Investments (Other Invested Assets) (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Other Invested Assets [Line Items]
Other invested assets	$ 1,203,591	$ 1,088,613
Total LPs/LLCs
Other Invested Assets [Line Items]
Other invested assets	1,168,574	1,040,992
Company’s investment in separate accounts
Other Invested Assets [Line Items]
Other invested assets	426	510
Derivative Instruments
Other Invested Assets [Line Items]
Other invested assets	34,591	47,111
Equity Method | Total LPs/LLCs
Other Invested Assets [Line Items]
Other invested assets	1,103,599	971,993
Equity Method | Private equity | Total LPs/LLCs
Other Invested Assets [Line Items]
Other invested assets	340,262	287,969
Equity Method | Hedge funds | Total LPs/LLCs
Other Invested Assets [Line Items]
Other invested assets	670,663	576,595
Equity Method | Real estate-related | Total LPs/LLCs
Other Invested Assets [Line Items]
Other invested assets	92,674	107,429
Fair Value | Total LPs/LLCs
Other Invested Assets [Line Items]
Other invested assets	64,975	68,999
Fair Value | Private equity | Total LPs/LLCs
Other Invested Assets [Line Items]
Other invested assets	56,468	59,146
Fair Value | Hedge funds | Total LPs/LLCs
Other Invested Assets [Line Items]
Other invested assets	194	396
Fair Value | Real estate-related | Total LPs/LLCs
Other Invested Assets [Line Items]
Other invested assets	$ 8,313	$ 9,457