Noncontrolling Interest (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	$ 266,056	$ 263,597
Net income (loss)	(2,436)	(11,602)
Stock based compensation	3,122	3,309
Exercise of options and warrants	39	195
Employee stock purchase plan	918	1,541
Foreign currency translation adjustment	(113)	400
Purchase of shares for treasury	(119)	(205)
Investments by noncontrolling interests		3,443
Ending balance	267,467	260,678
Comprehensive loss:
Net income (loss)	(2,436)	(11,602)
Other comprehensive income (loss):
Foreign currency translation adjustment	(113)	400
Comprehensive loss	(2,549)	(11,202)
On Deck Capital, Inc's stockholders' equity
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	262,045	259,525
Net income (loss)	(1,918)	(11,058)
Stock based compensation	3,122	3,309
Exercise of options and warrants	39	195
Employee stock purchase plan	918	1,541
Foreign currency translation adjustment	(63)	220
Purchase of shares for treasury	(119)	(205)
Investments by noncontrolling interests		0
Ending balance	264,024	253,527
Comprehensive loss:
Net income (loss)	(1,918)	(11,058)
Other comprehensive income (loss):
Foreign currency translation adjustment	(63)	220
Comprehensive loss	(1,981)	(10,838)
Noncontrolling interest
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	4,011	4,072
Net income (loss)	(518)	(544)
Stock based compensation	0	0
Exercise of options and warrants	0	0
Employee stock purchase plan	0	0
Foreign currency translation adjustment	(50)	180
Purchase of shares for treasury	0	0
Investments by noncontrolling interests		3,443
Ending balance	3,443	7,151
Comprehensive loss:
Net income (loss)	(518)	(544)
Other comprehensive income (loss):
Foreign currency translation adjustment	(50)	180
Comprehensive loss	$ (568)	$ (364)