Securitizations Net - Summary of Outstanding Balance Net of Discounts and Deals Costs of Securities and Effective Interest Rate (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Debt Instrument [Line Items]
Securitizations, net	$ 1,599,719	$ 1,261,456	$ 1,599,719	$ 1,261,456	$ 1,438,629
Interest expense — portfolio related	21,189	20,324	44,036	39,387
Average outstanding balance	$ 1,565,754	$ 1,277,009	$ 1,565,754	$ 1,277,009
Effective interest rate			4.74%	5.25%
Securitizations
Debt Instrument [Line Items]
Interest expense — portfolio related			$ 37,104	$ 33,553