Borrowings - Schedule of Other Secured Borrowings (Details) - USD ($)	Jun. 30, 2017	Dec. 31, 2016	Jun. 29, 2015
Debt Instrument [Line Items]
Less: deferred debt issuance costs	$ (6,840,000)	$ (6,000,000)
Other secured borrowings	$ 0	144,099,000
Secured debt
Debt Instrument [Line Items]
Less: deferred debt issuance costs		(872,000)
Other secured borrowings		$ 144,099,000
Secured debt | Asset-backed Securities Class A Notes 2015-1
Debt Instrument [Line Items]
Interest Rate		4.01%	4.01%
Amount Outstanding, before debt issuance costs deducted		$ 178,971,000
Intercompany eliminations		$ (34,000,000)
Other secured borrowings			$ 205,000,000.0
Secured debt | Asset-backed Securities Class M Notes 2015-1
Debt Instrument [Line Items]
Interest Rate		0.00%
Amount Outstanding, before debt issuance costs deducted		$ 60,000,000
Intercompany eliminations		$ (60,000,000)
Other secured borrowings			$ 60,000,000.0