Borrowings - Secured Financing (Details) - USD ($)	1 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Total Issued						$ 1,110,000,000	$ 1,900,500,000
Total loans and accrued interest amount securitized at inception						$ 1,208,963,000	$ 2,101,644,000
Issuance 2018-A
Debt Instrument [Line Items]
Total Issued					$ 670,000,000
Weighted Average Life (in years)					4 years 5 months 4 days
Basis spread on variable rate					0.78%
Issuance 2018-B
Debt Instrument [Line Items]
Total Issued				$ 686,500,000
Weighted Average Life (in years)				4 years 4 months 24 days
Basis spread on variable rate				0.76%
Issuance 2018-C
Debt Instrument [Line Items]
Total Issued			$ 544,000,000
Weighted Average Life (in years)			4 years 3 months 25 days
Basis spread on variable rate			0.77%
Issuance 2019-A
Debt Instrument [Line Items]
Total Issued		$ 453,000,000
Weighted Average Life (in years)		4 years 3 months 3 days
Basis spread on variable rate		0.92%
Issuance 2019-B
Debt Instrument [Line Items]
Total Issued	$ 657,000,000
Weighted Average Life (in years)	4 years 4 months 28 days
Basis spread on variable rate	1.01%