Noncontrolling Interest (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance			$ 329,422	$ 310,605
Net income (loss)	$ (17,173)	$ 3,507	(49,022)	2,912
Stock-based compensation			11,399	8,065
Employee stock purchase plan			3,996
Cumulative translation adjustment	210	(1,215)	393	(1,215)
Exercise of options and warrants			168	2,422
Purchase of shares for treasury			(576)
OnDeck Australia capitalization				6,870
Other				(183)
Ending balance	295,780	329,476	295,780	329,476
Comprehensive income (loss):
Net income (loss)	(17,173)	3,507	(49,022)	2,912
Foreign currency translation adjustment	210	(1,215)	393	(1,215)
Comprehensive income (loss):	(16,963)	2,292	(48,629)	1,697
On Deck Capital, Inc.'s stockholders' equity
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance			322,813	310,605
Net income (loss)			(47,102)	3,370
Stock-based compensation			11,399	8,065
Employee stock purchase plan			3,996
Cumulative translation adjustment			216	(669)
Exercise of options and warrants			168	2,422
Purchase of shares for treasury			(576)
OnDeck Australia capitalization				0
Other				(183)
Ending balance	290,914	323,610	290,914	323,610
Comprehensive income (loss):
Net income (loss)			(47,102)	3,370
Foreign currency translation adjustment			216	(669)
Comprehensive income (loss):			(46,886)	2,701
Noncontrolling interest
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance			6,609	0
Net income (loss)			(1,920)	(458)
Stock-based compensation			0	0
Employee stock purchase plan			0
Cumulative translation adjustment			177	(546)
Exercise of options and warrants			0	0
Purchase of shares for treasury			0
OnDeck Australia capitalization				6,870
Other				0
Ending balance	$ 4,866	$ 5,866	4,866	5,866
Comprehensive income (loss):
Net income (loss)			(1,920)	(458)
Foreign currency translation adjustment			177	(546)
Comprehensive income (loss):			$ (1,743)	$ (1,004)