Investments (Other Invested Assets) (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Other Invested Assets [Line Items]
Other invested assets	$ 1,465,970	$ 1,222,985
Total LPs/LLCs
Other Invested Assets [Line Items]
Other invested assets	1,457,141	1,204,869
Derivative Instruments
Other Invested Assets [Line Items]
Other invested assets	8,387	17,718
Other
Other Invested Assets [Line Items]
Other invested assets	442	398
Equity Method | Total LPs/LLCs
Other Invested Assets [Line Items]
Other invested assets	1,408,955	1,137,562
Equity Method | Private equity | Total LPs/LLCs
Other Invested Assets [Line Items]
Other invested assets	383,918	333,863
Equity Method | Hedge funds | Total LPs/LLCs
Other Invested Assets [Line Items]
Other invested assets	926,861	720,360
Equity Method | Real estate-related | Total LPs/LLCs
Other Invested Assets [Line Items]
Other invested assets	98,176	83,339
Fair Value | Total LPs/LLCs
Other Invested Assets [Line Items]
Other invested assets	48,186	67,307
Fair Value | Private equity | Total LPs/LLCs
Other Invested Assets [Line Items]
Other invested assets	31,762	48,483
Fair Value | Hedge funds | Total LPs/LLCs
Other Invested Assets [Line Items]
Other invested assets	14	137
Fair Value | Real estate-related | Total LPs/LLCs
Other Invested Assets [Line Items]
Other invested assets	$ 16,410	$ 18,687