Share-Based Compensation - Additional Information (Details) - USD ($)	3 Months Ended		6 Months Ended		12 Months Ended
	Jul. 03, 2018	Jul. 04, 2017	Jul. 03, 2018	Jul. 04, 2017	Jan. 02, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Employee service share-based compensation, tax benefit from compensation expense	$ 0	$ 0	$ 0	$ 0
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 3.44		$ 3.44	$ 3.54
Remaining expense to amortize	$ 1,400,000		$ 1,400,000
Share-based compensation arrangement by share-based payment award, options, vested and expected to vest, outstanding, weighted average remaining recognition period			1 year 7 months 6 days
Share-based Compensation Award, Tranche One [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, purchase price of common stock, percent			15.00%
Share-based Compensation Award, Tranche Two [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, purchase price of common stock, percent			22.50%
Share-based Compensation Award, Tranche Three [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, purchase price of common stock, percent			30.00%
Employee Stock Option [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, options, vested and expected to vest, outstanding, number	500,000		500,000
Inducement Awards [Member] \| Employee Stock Option [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, shares issued in period	48,000		48,000	15,000
Restricted Stock Units [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Accelerated share-based compensation expense	$ 700,000		$ 700,000
Cash-Based Bonus Award [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Accelerated share-based compensation expense	$ 1,100,000		$ 1,100,000
Time-Based Restricted Stock Units [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 9.71		$ 9.71
Number of shares, granted			198,000		0
Remaining vesting period	2 years		2 years
Share-based compensation arrangement by share-based payment award equity instruments other than options grants in period grant date fair value	$ 2,000,000		$ 2,000,000
Unvested share-based compensation	$ 400,000		$ 400,000
Share based compensation arrangement by share based payment award option and restricted stock, remaining weighted average vesting period			1 year
Weighted-Average Grant Date Fair Value, granted			$ 10.00
Time-Based Restricted Stock Units [Member] \| Non-Board Member [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares, granted	127,671		127,671
Time-Based Restricted Stock Units [Member] \| Board of Directors [Membe]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares, granted	70,206		70,206
Vesting period			1 year
Performance-Based Restricted Stock Units [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares, granted	0		0		0
Market-Based Restricted Stock Units [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares, granted	105,000	0	105,000	70,000
Unvested share-based compensation	$ 300,000		$ 300,000
Share based compensation arrangement by share based payment award option and restricted stock, remaining weighted average vesting period			2 years 6 months
Weighted-Average Grant Date Fair Value, granted	$ 3.51		$ 3.51	$ 1.06
Market-Based Restricted Stock Units [Member] \| Minimum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, estimated requisite service period			18 months
Market-Based Restricted Stock Units [Member] \| Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, estimated requisite service period			30 months
General and Administrative Expense [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Allocated share-based compensation expense	$ 2,100,000	$ 500,000	$ 2,200,000	$ 600,000

JAMBA, INC. 10-Q