Consolidated Statements of Operations and Comprehensive Income - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenue:
Interest income	$ 383,579,000	$ 334,575,000	$ 264,844,000
Gain on sales of loans	0	2,485,000	14,411,000
Other revenue	14,797,000	13,890,000	12,062,000
Gross revenue	398,376,000	350,950,000	291,317,000
Cost of revenue:
Provision for loan losses	148,541,000	152,926,000	149,963,000
Interest expense	47,075,000	46,199,000	32,862,000
Total cost of revenue	195,616,000	199,125,000	182,825,000
Net revenue	202,760,000	151,825,000	108,492,000
Operating expense:
Sales and marketing	44,082,000	52,786,000	67,011,000
Technology and analytics	50,866,000	53,392,000	58,899,000
Processing and servicing	21,209,000	18,076,000	19,719,000
General and administrative	61,333,000	41,916,000	48,345,000
Total operating expense	177,490,000	166,170,000	193,974,000
Income (loss) from operations, before provision for income taxes	25,270,000	(14,345,000)	(85,482,000)
Provision for income taxes	0	0	0
Net income (loss)	25,270,000	(14,345,000)	(85,482,000)
Unrealized (loss) on derivative instrument	(456,000)
Unrealized (loss) on derivative instrument		0	0
Less: Net income (loss) attributable to noncontrolling interest	(2,411,000)	(2,811,000)	(2,524,000)
Net income (loss) attributable to On Deck Capital, Inc. common stockholders	$ 27,681,000	$ (11,534,000)	$ (82,958,000)
Net income (loss) per share attributable to On Deck Capital, Inc. common stockholders:
Basic (in dollars per share)	$ 0.37	$ (0.16)	$ (1.17)
Diluted (in dollars per share)	$ 0.35	$ (0.16)	$ (1.17)
Weighted-average common shares outstanding:
Basic (in shares)	74,561,019	72,890,313	70,934,937
Diluted (in shares)	78,549,940	72,890,313	70,934,937
Comprehensive income (loss):
Foreign currency translation adjustment	$ (1,791,000)	$ 594,000	$ (20,000)
Comprehensive income (loss)	23,023,000	(13,751,000)	(85,502,000)
Less: Comprehensive income (loss) attributable to noncontrolling interests	467,000	(267,000)	13,000
Less: Net income (loss) attributable to noncontrolling interest	(2,411,000)	(2,811,000)	(2,524,000)
Comprehensive income (loss) attributable to On Deck Capital, Inc. common stockholders	$ 25,901,000	$ (11,207,000)	$ (82,965,000)