Organization and Summary of Significant Accounting Policies (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Apr. 01, 2019	Mar. 31, 2019	Jan. 01, 2019
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease, liability	$ 39.0
Operating lease, right-of-use asset					$ 27.6
Deferred rent and lease incentives					10.1
Operating lease, cost	$ 1.5
Operating lease, weighted average remaining lease term	7 years 2 months
Operating lease, weighted average discount rate, percent	7.00%
Accounting Standards Update 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease, liability					37.5
Operating lease, right-of-use asset					$ 37.5
On Deck Capital Canada
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Ownership percentage			58.50%
Restatement Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Under accrual of commissions on renewal loans		$ 2.4
Under accrual of commissions on renewal loans, percent		90.00%
Under accrual of commissions on renewal loans, portion of Stockholders' Equity, percent				1.00%
Under accrual of commissions on renewal loans, portion of commissions paid, percent				1.00%