Separate Accounts (Separate Account Assets) (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Fair Value, Separate Account Investment [Line Items]
Separate account assets	$ 119,188,485	$ 114,051,246
U.S. Treasury securities and obligations of U.S. government authorities and agencies
Fair Value, Separate Account Investment [Line Items]
Separate account assets	2,954	2,510
U.S. corporate securities
Fair Value, Separate Account Investment [Line Items]
Separate account assets	9,504	8,702
Foreign corporate securities
Fair Value, Separate Account Investment [Line Items]
Separate account assets	1,763	1,420
Mortgage-backed securities
Fair Value, Separate Account Investment [Line Items]
Separate account assets	186	276
Equity
Fair Value, Separate Account Investment [Line Items]
Separate account assets	72,614,821	67,144,660
Fixed Income
Fair Value, Separate Account Investment [Line Items]
Separate account assets	37,065,162	38,109,374
Other
Fair Value, Separate Account Investment [Line Items]
Separate account assets	4,101,661	3,441,016
Equity securities
Fair Value, Separate Account Investment [Line Items]
Separate account assets	104,159	49,260
Other invested assets
Fair Value, Separate Account Investment [Line Items]
Separate account assets	5,258,900	5,262,178
Short-term investments
Fair Value, Separate Account Investment [Line Items]
Separate account assets	2,126	1,237
Cash and cash equivalents
Fair Value, Separate Account Investment [Line Items]
Separate account assets	$ 27,249	$ 30,613