Variable Interest Entities - Narrative (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Variable Interest Entity [Line Items]
Accrued expenses and other liabilities	$ 243,207	$ 131,367
Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entity [Line Items]
Maximum loss	$ 223,509	32,466
Multifamily Loan Securitization, Liability | Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entity [Line Items]
Maximum loss, percentage of loans	10.00%
Maximum loss	$ 50,901	0
Multifamily Loan Securitization | Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entity [Line Items]
Accrued expenses and other liabilities	$ 448	$ 0