Derivative Instruments - Narrative (Details) - Not Designated as Hedging Instrument - USD ($)	Dec. 31, 2022	Dec. 31, 2021
Interest rate swaps
Derivative [Line Items]
Derivative, notional amount	$ 0	$ 0
Total return swaps
Derivative [Line Items]
Derivative, notional amount	0	0
Long | Interest rate futures
Derivative [Line Items]
Derivative, notional amount	2,400,000,000	2,200,000,000
Long | Foreign currency forward contracts
Derivative [Line Items]
Derivative, notional amount	861,700,000	915,000,000
Long | Foreign currency forward contracts
Derivative [Line Items]
Derivative, notional amount	225,600,000	245,800,000
Long | Credit default swaps
Derivative [Line Items]
Derivative, notional amount	13,100,000	0
Long | Equity futures
Derivative [Line Items]
Derivative, notional amount	116,000,000	74,300,000
Short | Interest rate futures
Derivative [Line Items]
Derivative, notional amount	500,000,000	500,000,000
Short | Foreign currency forward contracts
Derivative [Line Items]
Derivative, notional amount	172,400,000	329,300,000
Short | Foreign currency forward contracts
Derivative [Line Items]
Derivative, notional amount	86,300,000	131,000,000
Short | Credit default swaps
Derivative [Line Items]
Derivative, notional amount	$ 953,400,000	$ 218,500,000