Borrowings - Securitizations (Details) - USD ($) $ in Thousands	May 31, 2016	Jul. 31, 2015	Jun. 30, 2016	Dec. 31, 2015
Securities Financing Transaction [Line Items]
Total bonds issued			$ 501,000	$ 630,800
Total loan amount securitized at inception on-balance sheet term securitization	$ 619,944	$ 745,580
2015-B
Securities Financing Transaction [Line Items]
Total bonds issued		$ 630,800
Weighted Average Life		4 years 9 months 26 days
2016-A
Securities Financing Transaction [Line Items]
Total bonds issued	$ 501,000
Weighted Average Life	4 years 3 days
LIBOR | 2015-B
Securities Financing Transaction [Line Items]
Basis spread on variable rate		1.53%
LIBOR | 2016-A
Securities Financing Transaction [Line Items]
Basis spread on variable rate	1.38%