Derivative Instruments - Notional Value and Fair Value of Derivative Instruments (Details) - Not Designated as Hedging Instrument - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Derivative [Line Items]
Notional Value	$ 493,378	$ 510,544
Derivative Assets	24,428	24,712
Derivative Liabilities	10,722	13,712
Exchange-traded futures
Derivative [Line Items]
Notional Value	155,467	154,687
Derivative Assets	2,946	1,768
Derivative Liabilities	9	162
Currency forwards
Derivative [Line Items]
Notional Value	27,740	34,597
Derivative Assets	5,314	4,446
Derivative Liabilities	4,494	5,047
Interest rate swaps
Derivative [Line Items]
Notional Value	19,350	16,847
Derivative Assets	671	386
Derivative Liabilities	483	262
Credit default swaps
Derivative [Line Items]
Notional Value	170,418	225,671
Derivative Assets	13,130	17,507
Derivative Liabilities	5,234	7,302
Total return swaps
Derivative [Line Items]
Notional Value	70,403	28,742
Derivative Assets	2,367	605
Derivative Liabilities	3	933
Option swaps
Derivative [Line Items]
Notional Value	50,000	50,000
Derivative Assets	0	0
Derivative Liabilities	$ 499	$ 6