Noncontrolling Interest (Schedule of Changes in Equity, Including Equity Attributable to Noncontrolling Interests (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
	Jun. 29, 2017	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance				$ 266,056	$ 263,597
Net income (loss)		$ 4,774	$ (2,569)	2,338	(14,171)
Stock based compensation				5,834	6,134
Exercise of options and warrants				39	347
Employee stock purchase plan				968	1,618
Foreign currency translation adjustment		(396)	36	(509)	436
Purchase of treasury shares				(441)	(644)
Investments by noncontrolling interests				3,403	3,443
Return of equity to noncontrolling interests	$ (1,000)				(960)
Ending balance		277,688	259,800	277,688	259,800
Comprehensive loss:
Net income (loss)		4,774	(2,569)	2,338	(14,171)
Other comprehensive income (loss):
Foreign currency translation adjustment		(396)	36	(509)	436
Comprehensive income (loss)		4,378	(2,533)	1,829	(13,735)
On Deck Capital, Inc.'s stockholders' equity
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance				262,045	259,525
Net income (loss)				3,873	(12,556)
Stock based compensation				5,834	6,134
Exercise of options and warrants				39	347
Employee stock purchase plan				968	1,618
Foreign currency translation adjustment				(280)	240
Purchase of treasury shares				(441)	(644)
Investments by noncontrolling interests				0	0
Return of equity to noncontrolling interests					0
Ending balance		272,038	254,664	272,038	254,664
Comprehensive loss:
Net income (loss)				3,873	(12,556)
Other comprehensive income (loss):
Foreign currency translation adjustment				(280)	240
Comprehensive income (loss)				3,593	(12,316)
Noncontrolling interest
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance				4,011	4,072
Net income (loss)				(1,535)	(1,615)
Stock based compensation				0	0
Exercise of options and warrants				0	0
Employee stock purchase plan				0	0
Foreign currency translation adjustment				(229)	196
Purchase of treasury shares				0	0
Investments by noncontrolling interests				3,403	3,443
Return of equity to noncontrolling interests					(960)
Ending balance		$ 5,650	$ 5,136	5,650	5,136
Comprehensive loss:
Net income (loss)				(1,535)	(1,615)
Other comprehensive income (loss):
Foreign currency translation adjustment				(229)	196
Comprehensive income (loss)				$ (1,764)	$ (1,419)