Investments (Other Invested Assets) (Details) - USD ($) $ in Thousands	Mar. 31, 2025	Dec. 31, 2024
Other Invested Assets [Line Items]
Other invested assets	$ 2,040,612	$ 1,582,094
Total LPs/LLCs
Other Invested Assets [Line Items]
Other invested assets	1,935,074	1,533,210
Derivative Instruments
Other Invested Assets [Line Items]
Other invested assets	80,482	24,499
Other
Other Invested Assets [Line Items]
Other invested assets	25,056	24,385
Equity Method | Total LPs/LLCs
Other Invested Assets [Line Items]
Other invested assets	1,895,158	1,489,086
Equity Method | Private equity | Total LPs/LLCs
Other Invested Assets [Line Items]
Other invested assets	397,782	388,822
Equity Method | Hedge funds | Total LPs/LLCs
Other Invested Assets [Line Items]
Other invested assets	1,422,821	1,024,534
Equity Method | Real estate-related | Total LPs/LLCs
Other Invested Assets [Line Items]
Other invested assets	74,555	75,730
Fair Value | Total LPs/LLCs
Other Invested Assets [Line Items]
Other invested assets	39,916	44,124
Fair Value | Private equity | Total LPs/LLCs
Other Invested Assets [Line Items]
Other invested assets	24,326	28,094
Fair Value | Hedge funds | Total LPs/LLCs
Other Invested Assets [Line Items]
Other invested assets	15	14
Fair Value | Real estate-related | Total LPs/LLCs
Other Invested Assets [Line Items]
Other invested assets	$ 15,575	$ 16,016