Servicing Rights (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Transfers and Servicing [Abstract]
Serviced unpaid principal balance	$ 345.9	$ 79.7
Unpaid principal balance for loans sold during period	600.0	139.1	$ 17.5
Servicing revenue	$ 3.5	$ 0.9

Servicing Assets and Servicing Liabilities at Fair Value, Assumptions Used to Estimate Fair Value, Loans Sold During Period, Unpaid Principal Balance

No definition available.

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Namespace Prefix:	ondk_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration