Separate Accounts (Separate Account Assets) (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Fair Value, Separate Account Investment [Line Items]
Separate account assets	$ 122,779,095	$ 119,188,485
U.S. Treasury securities and obligations of U.S. government authorities and agencies
Fair Value, Separate Account Investment [Line Items]
Separate account assets	6,814	2,954
Obligations of U.S. states and their political subdivisions authorities
Fair Value, Separate Account Investment [Line Items]
Separate account assets	117	0
U.S. corporate securities
Fair Value, Separate Account Investment [Line Items]
Separate account assets	21,535	9,504
Foreign corporate securities
Fair Value, Separate Account Investment [Line Items]
Separate account assets	2,705	1,763
Asset-backed securities
Fair Value, Separate Account Investment [Line Items]
Separate account assets	1,029	0
Mortgage-backed securities
Fair Value, Separate Account Investment [Line Items]
Separate account assets	180	186
Equity
Fair Value, Separate Account Investment [Line Items]
Separate account assets	77,430,801	72,614,821
Fixed Income
Fair Value, Separate Account Investment [Line Items]
Separate account assets	34,531,108	37,065,162
Other
Fair Value, Separate Account Investment [Line Items]
Separate account assets	4,526,225	4,101,661
Equity securities
Fair Value, Separate Account Investment [Line Items]
Separate account assets	121,973	104,159
Other invested assets
Fair Value, Separate Account Investment [Line Items]
Separate account assets	6,078,743	5,258,900
Short-term investments
Fair Value, Separate Account Investment [Line Items]
Separate account assets	466	2,126
Cash and cash equivalents
Fair Value, Separate Account Investment [Line Items]
Separate account assets	$ 57,399	$ 27,249