SELF-STORAGE REAL ESTATE OWNED (Narrative) (Details) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($) property	Jun. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)	May 06, 2020	Apr. 10, 2020	Feb. 21, 2020	Feb. 14, 2020	Feb. 10, 2020	Sep. 17, 2019	Aug. 16, 2019	Mar. 08, 2019
Schedule of Investments [Line Items]
Investment commitment	$ 371,469		$ 371,469		$ 608,851
Funded Investment, outstanding	333,996		333,996		478,634
Development property investments, Fair Value	364,688		364,688		549,684
Cash consideration			$ 18,592	$ 81,500
Development Property Investments [Member]
Schedule of Investments [Line Items]
Number of investments \| property			20
Put option purchase price terms			The put, if exercised, requires the Company to purchase the member’s interest at the original purchase price plus a yield of 4.5% on such purchase price.
Development Property Investments [Member] \| Class A Membership Units [Member] \| New Haven [Member] \| Limited Liability Company that Owned the Property [Member]
Schedule of Investments [Line Items]
Minority interest, ownership percentage													100.00%
Development Property Investments [Member] \| Class A Membership Units [Member] \| Jacksonville 2 [Member] \| Limited Liability Company that Owned the Property [Member]
Schedule of Investments [Line Items]
Minority interest, ownership percentage												100.00%
Development Property Investments [Member] \| Class A Membership Units [Member] \| Miami 4, Miami 5, Miami 6, Miami 7 and Miami 8 [Member} \| Limited Liability Company that Owned the Property [Member]
Schedule of Investments [Line Items]
Minority interest, ownership percentage											100.00%
Development Property Investments [Member] \| Loan Investments [Member]
Schedule of Investments [Line Items]
Number of investments \| property			34
Investment commitment	$ 316,498		$ 316,498		553,880
Equity method investment, ownership percentage	49.90%		49.90%
Mortgage loans on real estate, interest rate			6.90%
Mortgage loans on real estate, periodic payment terms			typically have a term of 72 months
Development property investments, Fair Value	$ 303,764		$ 303,764		490,651
In-place leases	5,700		5,700
Development property investment, assets	433,700		433,700		592,300
Development property investment, liabilities	392,400		392,400		531,700
Development property investment, revenue	2,000	$ 2,600	3,600	4,400
Development property investment, operating expenses	1,800	$ 2,800	3,300	$ 5,000
Development Property Investments [Member] \| Loan Investments [Member] \| Atlanta 4 [Member]
Schedule of Investments [Line Items]
Investment commitment					13,678
Development property investments, Fair Value					17,082
Development Property Investments [Member] \| Loan Investments [Member] \| Houston [Member]
Schedule of Investments [Line Items]
Investment commitment	14,825		14,825		14,825
Funded Investment, outstanding	14,800		14,800
Development property investments, Fair Value	15,661		15,661		17,820
Development Property Investments [Member] \| Loan Investments [Member] \| Miami [Member]
Schedule of Investments [Line Items]
Land					3,900
Construction-in-progress					16,500
Development Property Investments [Member] \| Loan Investments [Member] \| Philadelphia [Member]
Schedule of Investments [Line Items]
Investment commitment	14,338		14,338		14,338
Funded Investment, outstanding	11,500		11,500
Development property investments, Fair Value	$ 11,313		$ 11,313		11,807
Development Property Investments [Member] \| Loan Investments [Member] \| Raleigh [Member]
Schedule of Investments [Line Items]
Investment commitment					8,792
Development property investments, Fair Value					8,593
Development Property Investments [Member] \| Loan Investments [Member] \| Jacksonville 3 [Member]
Schedule of Investments [Line Items]
Investment commitment					8,096
Development property investments, Fair Value					10,129
Development Property Investments [Member] \| Loan Investments [Member] \| Class A Membership Units [Member] \| Charlotte II, Knoxville, Louisville I, Atlanta III, Atlanta V And Atlanta VI [Member] \| Limited Liability Company that Owned the Property [Member]
Schedule of Investments [Line Items]
Minority interest, ownership percentage										100.00%
Development Property Investments [Member] \| Loan Investments [Member] \| Class A Membership Units [Member] \| Fort Lauderdale And Boston 2 [Member] \| Limited Liability Company that Owned the Property [Member]
Schedule of Investments [Line Items]
Minority interest, ownership percentage									100.00%
Development Property Investments [Member] \| Loan Investments [Member] \| Class A Membership Units [Member] \| Atlanta 4 [Member] \| Limited Liability Company that Owned the Property [Member]
Schedule of Investments [Line Items]
Minority interest, ownership percentage								100.00%
Development Property Investments [Member] \| Loan Investments [Member] \| Class A Membership Units [Member] \| Raleigh [Member] \| Limited Liability Company that Owned the Property [Member]
Schedule of Investments [Line Items]
Minority interest, ownership percentage							100.00%
Development Property Investments [Member] \| Loan Investments [Member] \| Class A Membership Units [Member] \| Jacksonville 3 [Member] \| Limited Liability Company that Owned the Property [Member]
Schedule of Investments [Line Items]
Minority interest, ownership percentage						100.00%
Development Property Investments [Member] \| Loan Investments [Member] \| Class A Membership Units [Member] \| Minneapolis 1, Minneapolis 2, and Minneapolis 3 [Member] \| Limited Liability Company that Owned the Property [Member]
Schedule of Investments [Line Items]
Minority interest, ownership percentage	100.00%		100.00%
Development Property Investments [Member] \| Preferred Equity Investments [Member]
Schedule of Investments [Line Items]
Investment commitment	$ 54,971		$ 54,971		$ 54,971
Equity method investment, ownership percentage	90.00%		90.00%		90.00%
Development property investments, Fair Value	$ 60,924		$ 60,924		$ 59,033
Development Property Investments [Member] \| Preferred Equity Investments [Member] \| Minimum [Member]
Schedule of Investments [Line Items]
Percentage of financing provided by a traditional bank			60.00%
Development Property Investments [Member] \| Preferred Equity Investments [Member] \| Maximum [Member]
Schedule of Investments [Line Items]
Percentage of financing provided by a traditional bank			70.00%
Five Development Property Investments [Member] \| Preferred Equity Investments [Member]
Schedule of Investments [Line Items]
Number of investments \| property			5
Investment commitment	55,000		$ 55,000
Development Property Investment or Bridge Investment [Member] \| Loan Investments [Member]
Schedule of Investments [Line Items]
Development property investments, Fair Value	205,200		205,200		125,700
Acquisition date basis of investment	244,700		244,700		138,900
Cash consideration			30,000		10,500
Issuance of Operating Company ("OC") Units			6,700
In-place leases					5,100
Funded Investment [Member]
Schedule of Investments [Line Items]
Funded Investment, outstanding	333,996		333,996		478,634
Funded Investment [Member] \| Development Property Investments [Member] \| Loan Investments [Member]
Schedule of Investments [Line Items]
Funded Investment, outstanding	275,487		275,487		422,034
Funded Investment [Member] \| Development Property Investments [Member] \| Loan Investments [Member] \| Atlanta 4 [Member]
Schedule of Investments [Line Items]
Funded Investment, outstanding					13,497
Funded Investment [Member] \| Development Property Investments [Member] \| Loan Investments [Member] \| Houston [Member]
Schedule of Investments [Line Items]
Funded Investment, outstanding	14,825		14,825		14,825
Funded Investment [Member] \| Development Property Investments [Member] \| Loan Investments [Member] \| Philadelphia [Member]
Schedule of Investments [Line Items]
Funded Investment, outstanding	11,536		11,536		11,536
Funded Investment [Member] \| Development Property Investments [Member] \| Loan Investments [Member] \| Raleigh [Member]
Schedule of Investments [Line Items]
Funded Investment, outstanding					8,789
Funded Investment [Member] \| Development Property Investments [Member] \| Loan Investments [Member] \| Jacksonville 3 [Member]
Schedule of Investments [Line Items]
Funded Investment, outstanding					7,751
Funded Investment [Member] \| Development Property Investments [Member] \| Preferred Equity Investments [Member]
Schedule of Investments [Line Items]
Funded Investment, outstanding	$ 58,509		$ 58,509		$ 56,600

Jernigan Capital, Inc. 10-Q