Use of Special Purpose Entities (SPE) and Variable Interest Entities (VIE) - Financing VIEs Securitized Debt by Contractual Maturity (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Variable Interest Entity [Line Items]
Carrying value	$ 158,867	$ 116,541
Financing VIE
Variable Interest Entity [Line Items]
Within 24 months	0	89,509
Over 24 months to 36 months	132,319	0
Over 36 months	33,553	33,781
Total	165,872	123,290
Discount	(5,589)	(5,763)
Debt Issuance Costs, Net	(1,416)	(986)
Carrying value	$ 158,867	$ 116,541