Variable Interest Entities - Nonconsolidated VIEs (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Variable Interest Entity [Line Items]
Asset	$ 10,429,477	$ 9,965,798
Liability	8,628,764	8,110,760
Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entity [Line Items]
Asset	30,388	28,969
Liability	0	0
Maximum Exposure to Loss	30,388	28,969
VIEs' assets	$ 154,789	$ 175,547