Debt - Narrative (Details)										1 Months Ended					3 Months Ended				12 Months Ended		25 Months Ended
Debt - Narrative (Details)	Sep. 22, 2020 USD ($) $ / shares	Jul. 20, 2020 USD ($) loan $ / shares shares	May 28, 2020 USD ($) $ / shares	Apr. 06, 2020 USD ($) $ / shares shares	Oct. 31, 2019 USD ($) $ / shares	Sep. 18, 2019 USD ($)	Dec. 21, 2018 USD ($)	Dec. 13, 2018 USD ($)	Apr. 27, 2018 USD ($) $ / shares	Dec. 31, 2019 USD ($) $ / shares	Nov. 30, 2019 USD ($)	Apr. 30, 2019 USD ($)	Jan. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2020 USD ($) $ / shares shares	Jun. 30, 2020 USD ($)	Mar. 31, 2020 USD ($) $ / shares	Mar. 31, 2019 USD ($)	Dec. 31, 2020 USD ($) $ / shares shares	Dec. 31, 2019 USD ($) $ / shares	Dec. 31, 2020 USD ($) $ / shares shares	Nov. 02, 2020	Sep. 30, 2020 USD ($)	May 15, 2020	Dec. 22, 2014 USD ($)	Dec. 16, 2014 USD ($)
Debt Instrument [Line Items]
Stated interest rate																								1.00%
Proceeds from revolver																			$ 0	$ 12,500,000
Partial extinguishment of equity component																			2,528,000
Derivative liabilities										$ 6,776,000					$ 7,507,000				7,507,000	6,776,000	$ 7,507,000
Stockholders' equity note, stock split, conversion ratio			0.1
Derivative liability			$ 6,300,000
Derivative, excluded component, loss, recognized in earnings																$ 3,500,000			3,500,000
Loss on debt restructuring																			(51,858,000)	920,000
Inducement loss																			9,183,000	0
Extinguishment of prior term loan																			0	185,000
Change in the fair value of derivative liabilities																			$ (2,305,000)	6,769,000
Exercisable pre-reverse stock split, up to (in shares) \| shares				538,995											538,995				538,995		538,995
Exercise price, pre-reverse stock split (in dollars per share) \| $ / shares		$ 0.01		$ 0.01											$ 0.01				$ 0.01		$ 0.01
Warrants not settleable in cash, fair value disclosure			$ 2,200,000	$ 1,400,000											$ 300,000				$ 300,000		$ 300,000
Warrants and rights outstanding, term		5 years
Exercisable warrants (in shares) (up to) \| shares		134,667
Warrants outstanding (in shares) \| shares															134,667				134,667		134,667
Common Stock
Debt Instrument [Line Items]
Debt conversion, converted instrument, shares issued (in shares) \| shares																			16,362,654
Expected Life in Years \| Derivative liabilities related to Warrants
Debt Instrument [Line Items]
Warrants and rights outstanding, term		5 years	4 years 10 months 9 days	5 years
2023 Series A Unsecured Convertible Notes for Series B Senior Unsecured Convertible Notes
Debt Instrument [Line Items]
Debt issuance costs															$ 1,400,000				$ 1,400,000		$ 1,400,000
Fair value of embedded derivative liability					$ 2,000,000.0
Original derivative amount, before re-measurement					13,500,000
Derivative liabilities																	$ 2,800,000
Gain on change in fair value of derivatives																	4,000,000.0
Loss on debt restructuring																			900,000
Revolving Credit Facility
Debt Instrument [Line Items]
Derivative liability																$ 5,600,000
Change in the fair value of derivative liabilities																			5,600,000
Convertible Debt
Debt Instrument [Line Items]
Loss on debt extinguishment																			(11,800,000)
Partial extinguishment of equity component																			16,200,000
Unamortized discount															14,600,000				14,600,000		14,600,000
Loss on debt restructuring																			(1,200,000)
Lender fees																			1,800,000
Third party fees																			2,200,000
Adjustments to additional paid in capital, equity component of convertible debt, subsequent adjustments																			1,000,000.0
Convertible Notes Payable
Debt Instrument [Line Items]
Principal										213,959,000					181,580,000				181,580,000	213,959,000	181,580,000
Carrying value of original debt										186,370,000					162,246,000				162,246,000	186,370,000	162,246,000
Line of Credit
Debt Instrument [Line Items]
Proceeds from revolver														$ 52,800,000
Interest rate, effective percentage				4.25%
Covenant, revenue required to attain																			125,000,000.0
Liquidity of the Company and its subsidiaries				$ 10,000,000.0											10,000,000.0				10,000,000.0		10,000,000.0
Line of Credit \| Revolving Credit Facility
Debt Instrument [Line Items]
Principal										25,000,000					25,000,000				$ 25,000,000	25,000,000	25,000,000
Proceeds from revolver						$ 2,500,000		$ 15,000,000.0				$ 5,000,000.0	$ 5,000,000.0
Debt issuance costs								300,000
Unamortized discount								500,000
Line of credit maximum borrowing capacity														25,000,000.0
Repayment fee											$ 100,000
Line of Credit \| Revolving Credit Facility \| LIBOR
Debt Instrument [Line Items]
Applicable margin																			3.75%
Line of Credit \| Revolving Credit Facility \| LIBOR \| Minimum
Debt Instrument [Line Items]
Applicable margin				1.50%
Line of Credit \| Revolving Credit Facility \| LIBOR \| Maximum
Debt Instrument [Line Items]
Applicable margin				5.50%
Line of Credit \| Revolving Credit Facility \| Base Rate
Debt Instrument [Line Items]
Applicable margin				4.50%															2.75%
Line of Credit \| Term Loan
Debt Instrument [Line Items]
Principal								80,000,000.0
Debt issuance costs								800,000
Unamortized discount								1,800,000
Line of Credit \| Term Loan \| LIBOR
Debt Instrument [Line Items]
Applicable margin																			8.75%
Line of Credit \| Term Loan \| LIBOR \| Minimum
Debt Instrument [Line Items]
Applicable margin				1.50%
Line of Credit \| Term Loan \| LIBOR \| Maximum
Debt Instrument [Line Items]
Applicable margin				13.00%
Line of Credit \| Term Loan \| Base Rate
Debt Instrument [Line Items]
Applicable margin				12.00%															7.75%
Revolving Credit Facility \| Convertible Notes Payable
Debt Instrument [Line Items]
Principal										$ 25,000,000					$ 25,000,000				$ 25,000,000	$ 25,000,000	25,000,000
Qualified Institutional Buyers
Debt Instrument [Line Items]
Principal																									$ 18,750,000	$ 125,000,000.0
2019 Notes \| Convertible Debt
Debt Instrument [Line Items]
Stated interest rate																									3.75%	3.75%
Debt transfer amount									$ 75,100,000
Note 2023 \| Convertible Debt
Debt Instrument [Line Items]
Stated interest rate									4.75%
Debt transfer amount									$ 75,100,000
Conversion price (in dollars per share) \| $ / shares									$ 44.50
Senior Notes, due December 2019
Debt Instrument [Line Items]
Loss on debt extinguishment														1,700,000				$ 200,000
Partial extinguishment of equity component														2,900,000
Senior Notes, due December 2019 \| Convertible Debt
Debt Instrument [Line Items]
Proceeds from convertible debt					$ 29,300,000
Senior Notes, due December 2019 \| Convertible Notes Payable
Debt Instrument [Line Items]
Stated interest rate										3.75%										3.75%
Senior Notes, due December 2019 \| Convertible Debt
Debt Instrument [Line Items]
Debt transfer amount									$ 75,100,000
Transaction costs														$ 300,000
Loss on debt extinguishment									2,500,000
Partial extinguishment of equity component									$ 7,600,000
Repayment of term loan										$ 13,000,000.0								$ 2,700,000
Initial Term Loan
Debt Instrument [Line Items]
Paid-in-kind option, increase to principal balance																			$ 14,400,000		$ 22,900,000
Paid-in-kind interest option, term																			24 months
Initial Term Loan \| Minimum
Debt Instrument [Line Items]
Interest rate, effective percentage															16.60%				16.60%		16.60%
Initial Term Loan \| Maximum
Debt Instrument [Line Items]
Interest rate, effective percentage															17.70%				17.70%		17.70%
Initial Term Loan \| Line of Credit \| Term Loan
Debt Instrument [Line Items]
Principal								50,000,000.0
Delayed Draw Term Loan A \| Term Loan
Debt Instrument [Line Items]
Proceeds from revolver										10,000,000.0
Amount drawn on term loan							$ 20,000,000.0
Delayed Draw Term Loan A \| Term Loan \| Minimum
Debt Instrument [Line Items]
Interest rate, effective percentage															9.60%				9.60%		9.60%
Delayed Draw Term Loan A \| Term Loan \| Maximum
Debt Instrument [Line Items]
Interest rate, effective percentage															10.90%				10.90%		10.90%
Delayed Draw Term Loan A \| Line of Credit \| Term Loan
Debt Instrument [Line Items]
Principal								30,000,000.0
Delayed Draw Term Loan B \| Line of Credit \| Term Loan
Debt Instrument [Line Items]
Principal								$ 15,000,000.0
Extinguishment of prior term loan										15,000,000.0
2023 Series B Convertible Notes
Debt Instrument [Line Items]
Derivative liability			$ 6,300,000
2023 Series B Convertible Notes \| Convertible Debt
Debt Instrument [Line Items]
Stated interest rate					7.00%
Principal			$ 34,405,000							$ 34,405,000							$ 34,405,000			$ 34,405,000
Conversion price (in dollars per share) \| $ / shares			$ 7.20		$ 7.20					$ 7.20							$ 7.20			$ 7.20
Debt issuance costs					$ 2,300,000
Proceeds from convertible debt					34,400,000
Debt conversion, original amount	$ 400,000
Debt conversion, converted instrument	$ 500,000
Net proceeds from the financing					$ 26,900,000
PIK interest, percentage					8.00%
Debt instrument, discount on face amount	31.90%
Debt instrument, convertible, extinguishment of liability component															$ 500,000				$ 500,000		$ 500,000
2023 Series B Convertible Notes \| Convertible Debt \| Series B Convertible Note Holders
Debt Instrument [Line Items]
Stated interest rate		7.00%
Debt instrument, discount on face amount		10.00%
2023 Series B Convertible Notes \| Convertible Debt \| 2023 Note Holders
Debt Instrument [Line Items]
Debt instrument, discount on face amount		55.00%
2023 Series B Convertible Notes \| Convertible Debt \| 2023 Series A Unsecured Convertible Notes for Series B Senior Unsecured Convertible Notes
Debt Instrument [Line Items]
Debt issuance costs															200,000				200,000		200,000
Debt conversion, converted instrument					$ 5,100,000
Paid-in-kind option, increase to principal balance																			2,000,000.0
Carrying value of original debt															7,200,000				7,200,000		7,200,000
Fair value of embedded derivative liability															2,000,000.0				2,000,000.0		2,000,000.0
Future undiscounted cash flows															6,800,000				6,800,000		6,800,000
2023 Series B Convertible Notes \| Convertible Notes Payable
Debt Instrument [Line Items]
Principal										$ 34,405,000					0				0	$ 34,405,000	0
Series A Unsecured Convertible Notes due 2023 \| Convertible Debt
Debt Instrument [Line Items]
Debt conversion, converted instrument	$ 59,000,000.0
Debt instrument, discount on face amount	53.40%
Debt instrument, convertible, extinguishment of liability component															$ 19,300,000				$ 19,300,000		$ 19,300,000
Series A Unsecured Convertible Notes due 2023 \| Convertible Debt \| 2023 Series A Unsecured Convertible Notes for Series B Senior Unsecured Convertible Notes
Debt Instrument [Line Items]
Debt conversion, original amount					$ 9,000,000.0
Senior Notes, Due 2023
Debt Instrument [Line Items]
Effective interest rate															27.40%				27.40%		27.40%
Senior Notes, Due 2023 \| Convertible Debt
Debt Instrument [Line Items]
Stated interest rate									4.75%
Debt issuance costs									$ 1,600,000
Unamortized discount									$ 19,000,000.0
Interest rate, effective percentage									11.90%
Face amount of the 2023 Loan (due February 2023) \| Convertible Notes Payable
Debt Instrument [Line Items]
Principal										88,464,000					$ 102,905,000				$ 102,905,000	88,464,000	$ 102,905,000
2023 Series C Convertible Notes \| Convertible Debt
Debt Instrument [Line Items]
Stated interest rate		9.50%																				18.00%
Principal		$ 13,800,000
Conversion price (in dollars per share) \| $ / shares		$ 2.78
Proceeds from convertible debt		$ 10,000,000.0
Debt conversion, original amount		$ 32,300,000
Paid-in-kind option, increase to principal balance																			500,000
Debt instrument, convertible, conversion premium		20.00%
Debt instrument, convertible, threshold trading days \| loan		10
Debt instrument, covenant, default threshold		25.00%
2023 Series C Convertible Notes \| Convertible Debt \| Debt Instrument, Redemption, Period Two
Debt Instrument [Line Items]
Debt instrument, redemption price, percentage		75.00%
2023 Series C Convertible Notes \| Convertible Debt \| Debt Instrument, Redemption, Period Three
Debt Instrument [Line Items]
Debt instrument, redemption price, percentage		50.00%
2023 Series C Convertible Notes \| Convertible Debt \| Series B Convertible Note Holders
Debt Instrument [Line Items]
Debt conversion, converted instrument		$ 35,900,000
2023 Series C Convertible Notes \| Convertible Debt \| 2023 Note Holders
Debt Instrument [Line Items]
Debt conversion, original amount		3,700,000
Debt conversion, converted instrument		$ 8,200,000
2023 Series C Convertible Notes \| Convertible Debt \| Maximum
Debt Instrument [Line Items]
Stated interest rate		18.00%
2023 Series C Convertible Notes \| Convertible Notes Payable
Debt Instrument [Line Items]
Principal										0					50,323,000				50,323,000	0	50,323,000
2023 Series D Convertible Notes \| Convertible Debt
Debt Instrument [Line Items]
Loss on debt extinguishment																			$ (42,700,000)
Conversion price (in dollars per share) \| $ / shares	$ 1.50
Debt issuance costs																							$ 600,000
Debt conversion, original amount	$ 27,500,000
Debt conversion, converted instrument															$ 24,500,000
Debt instrument, covenant, default threshold															25.00%
Debt conversion, converted instrument, shares issued (in shares) \| shares															16,400,000
Debt conversion, converted instrument, rate																			666.6667%
Inducement loss																			$ 9,200,000
2023 Series D Convertible Notes \| Convertible Debt \| Common Stock
Debt Instrument [Line Items]
Inducement loss																			24,500,000
2023 Series D Convertible Notes \| Convertible Notes Payable
Debt Instrument [Line Items]
Principal										$ 0					$ 3,352,000				$ 3,352,000	$ 0	$ 3,352,000
2023 Series A Unsecured Convertible Notes for Series B Senior Unsecured Convertible Notes \| Convertible Debt
Debt Instrument [Line Items]
Principal	50,100,000
Debt conversion, converted instrument	$ 27,900,000

Teligent, Inc. 10-K