Derivative Instruments - Narrative (Details) - Not Designated as Hedging Instrument - USD ($)	Dec. 31, 2023	Dec. 31, 2022
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	5,900,000,000	2,400,000,000
Long | Foreign currency forward contracts
Derivative [Line Items]
Derivative, notional amount	805,200,000	861,700,000
Long | Foreign currency forward contracts
Derivative [Line Items]
Derivative, notional amount	420,700,000	225,600,000
Long | Credit default swaps
Derivative [Line Items]
Derivative, notional amount	22,100,000	953,400,000
Long | Equity futures
Derivative [Line Items]
Derivative, notional amount	0	116,000,000
Long | Commodity futures
Derivative [Line Items]
Derivative, notional amount	255,200,000	0
Long | Commodity options
Derivative [Line Items]
Derivative, notional amount	400,000	0
Short | Interest rate futures
Derivative [Line Items]
Derivative, notional amount	2,700,000,000	500,000,000
Short | Foreign currency forward contracts
Derivative [Line Items]
Derivative, notional amount	496,400,000	172,400,000
Short | Foreign currency forward contracts
Derivative [Line Items]
Derivative, notional amount	130,000,000	86,300,000
Short | Credit default swaps
Derivative [Line Items]
Derivative, notional amount	1,500,000,000	13,100,000
Short | Commodity options
Derivative [Line Items]
Derivative, notional amount	$ 0	$ 0