Derivative Contracts - Credit-risk related Contingent Features (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Derivative Instruments, Gain (Loss) [Line Items]
Percentage of notional amount disclosed	100.00%
Unconsolidated Funds
Derivative Instruments, Gain (Loss) [Line Items]
Percentage of notional amount disclosed	100.00%
Interest Rate Swap | Derivatives Designated as Cash Flow Hedges | Cash Flow Hedging
Derivative Instruments, Gain (Loss) [Line Items]
Fair value derivatives in net liability position	$ 254,268	$ 56,896
Percentage of notional amount disclosed	100.00%
Interest Rate Swap | Derivatives Designated as Cash Flow Hedges | Cash Flow Hedging | Unconsolidated Funds
Derivative Instruments, Gain (Loss) [Line Items]
Fair value derivatives in net liability position	$ 412	$ 0
Percentage of notional amount disclosed	100.00%