Separate Accounts (Separate Account Assets) (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Fair Value, Separate Account Investment [Line Items]
Separate account assets	$ 111,611,386	$ 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	2,439	2,510
U.S. corporate securities
Fair Value, Separate Account Investment [Line Items]
Separate account assets	4,289	8,702
Foreign corporate securities
Fair Value, Separate Account Investment [Line Items]
Separate account assets	1,614	1,420
Mortgage-backed securities
Fair Value, Separate Account Investment [Line Items]
Separate account assets	177	276
Equity
Fair Value, Separate Account Investment [Line Items]
Separate account assets	64,287,893	67,144,660
Fixed Income
Fair Value, Separate Account Investment [Line Items]
Separate account assets	38,483,909	38,109,374
Other
Fair Value, Separate Account Investment [Line Items]
Separate account assets	3,777,729	3,441,016
Equity securities
Fair Value, Separate Account Investment [Line Items]
Separate account assets	83,292	49,260
Other invested assets
Fair Value, Separate Account Investment [Line Items]
Separate account assets	4,958,037	5,262,178
Short-term investments
Fair Value, Separate Account Investment [Line Items]
Separate account assets	9,688	1,237
Cash and cash equivalents
Fair Value, Separate Account Investment [Line Items]
Separate account assets	$ 2,319	$ 30,613