Variable Interest Entities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Variable Interest Entity [Line Items]
VIE Assets	$ 2,009,051	$ 2,201,874
VIE Liabilities	1,542,684	1,713,108
Nonrecourse | Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
VIE Liabilities	1,414,303	1,551,203
Nonrecourse | Secured Financing [Member] | Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
VIE Liabilities	246,994	62,000
Nonrecourse | Liabilities at Fair Value [Member] | Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
VIE Liabilities	1,167,309	1,129,202
Nonrecourse | Asset-backed Notes at Amortized Cost [Member] | Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
VIE Liabilities	0	360,001
Asset Pledged as Collateral | Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
VIE Assets	1,617,978	1,831,907
Asset Pledged as Collateral | Restricted Cash [Member] | Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
VIE Assets	23,726	28,821
Asset Pledged as Collateral | Loans Receivable [Member] | Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
VIE Assets	1,580,061	1,745,465
Asset Pledged as Collateral | Loans Receivable at Amortized Cost [Member] | Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
VIE Assets	0	41,747
Asset Pledged as Collateral | Financing Receivable [Member] | Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
VIE Assets	$ 14,191	$ 15,874