Investments - Schedule of Investment Funds (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2025	Dec. 31, 2024
Alternative Investment [Line Items]
Investment funds, unfunded commitments	$ 471,000
Minimum
Alternative Investment [Line Items]
Expected life of non-redeemable funds	7 years
Extension options term of non-redeemable funds	1 year
Expected life of redeemable funds	6 months
Maximum
Alternative Investment [Line Items]
Expected life of non-redeemable funds	12 years
Extension options term of non-redeemable funds	4 years
Expected life of redeemable funds	36 months
Commercial mortgage loans
Alternative Investment [Line Items]
Investment funds, Fair Value	$ 547,663	$ 566,142
Investment funds, unfunded commitments	190,366
Opportunistic and private credit
Alternative Investment [Line Items]
Investment funds, Fair Value	216,659	202,008
Investment funds, unfunded commitments	204,013
Infrastructure
Alternative Investment [Line Items]
Investment funds, Fair Value	188,605	179,627
Investment funds, unfunded commitments	21,662
Other
Alternative Investment [Line Items]
Investment funds, Fair Value	84,520	38,989
Investment funds, unfunded commitments	54,793
Investment funds
Alternative Investment [Line Items]
Investment funds, Fair Value	1,037,447	$ 986,766
Investment funds, unfunded commitments	470,834
Unfunded commitments, including past investment period	$ 628,000