Debt (Details) - USD ($)	Dec. 31, 2019	Oct. 01, 2019	Jul. 19, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Weighted Average Interest Rate at December 31, 2019	3.80%
Debt	$ 922,701,000
Total Debt	$ 914,995,000			$ 816,231,000
OnDeck Asset Securitization Trust II LLC 2018-1 | Secured Debt
Debt Instrument [Line Items]
Weighted Average Interest Rate at December 31, 2019	3.80%
Debt	$ 225,000,000			225,000,000
OnDeck Asset Securitization Trust II LLC 2019-1 | Secured Debt
Debt Instrument [Line Items]
Weighted Average Interest Rate at December 31, 2019	3.04%
Debt	$ 125,000,000			0
OnDeck Account Receivables Trust 2013-1 | Revolving Credit Facility
Debt Instrument [Line Items]
Weighted Average Interest Rate at December 31, 2019	3.40%
Debt	$ 129,512,000			117,664,000
Receivable Assets of OnDeck, LLC | Revolving Credit Facility
Debt Instrument [Line Items]
Weighted Average Interest Rate at December 31, 2019	3.30%
Debt	$ 94,099,000			113,631,000
OnDeck Asset Funding II LLC | Revolving Credit Facility
Debt Instrument [Line Items]
Weighted Average Interest Rate at December 31, 2019	4.70%
Debt	$ 123,840,000			109,568,000
Prime OnDeck Receivable Trust II | Revolving Credit Facility
Debt Instrument [Line Items]
Weighted Average Interest Rate at December 31, 2019	3.80%
Debt	$ 0			108,816,000
Loan Assets of OnDeck, LLC | Revolving Credit Facility
Debt Instrument [Line Items]
Weighted Average Interest Rate at December 31, 2019	3.40%
Debt	$ 120,665,000			100,000,000
Corporate line of credit | Revolving Credit Facility
Debt Instrument [Line Items]
Weighted Average Interest Rate at December 31, 2019	4.70%
Debt	$ 40,000,000	$ 20,000,000	$ 20,000,000	0
International and other agreements
Debt Instrument [Line Items]
Weighted Average Interest Rate at December 31, 2019	4.90%
Debt	$ 64,585,000			47,318,000
Debt
Debt Instrument [Line Items]
Debt	922,701,000			821,997,000
Deferred debt issuance cost	(7,706,000)			(5,766,000)
Total Debt	$ 914,995,000			$ 816,231,000