Separate Accounts (Separate Account Assets) (Details) - USD ($) $ in Thousands	Sep. 30, 2025	Dec. 31, 2024
Fair Value, Separate Account Investment [Line Items]
Separate account assets	$ 119,905,139	$ 118,143,256
U.S. Treasury securities and obligations of U.S. government authorities and agencies
Fair Value, Separate Account Investment [Line Items]
Separate account assets	24,350	15,548
Obligations of U.S. states and their political subdivisions authorities
Fair Value, Separate Account Investment [Line Items]
Separate account assets	117	115
U.S. corporate securities
Fair Value, Separate Account Investment [Line Items]
Separate account assets	51,055	24,458
Foreign corporate securities
Fair Value, Separate Account Investment [Line Items]
Separate account assets	3,443	3,158
Asset-backed securities
Fair Value, Separate Account Investment [Line Items]
Separate account assets	791	1,099
Mortgage-backed securities
Fair Value, Separate Account Investment [Line Items]
Separate account assets	157	82
Equity
Fair Value, Separate Account Investment [Line Items]
Separate account assets	75,160,096	73,226,610
Fixed Income
Fair Value, Separate Account Investment [Line Items]
Separate account assets	31,544,612	33,828,097
Other
Fair Value, Separate Account Investment [Line Items]
Separate account assets	5,319,636	4,431,975
Equity securities
Fair Value, Separate Account Investment [Line Items]
Separate account assets	243,874	126,792
Other invested assets
Fair Value, Separate Account Investment [Line Items]
Separate account assets	7,520,085	6,444,077
Short-term investments
Fair Value, Separate Account Investment [Line Items]
Separate account assets	3,750	2,559
Cash and cash equivalents
Fair Value, Separate Account Investment [Line Items]
Separate account assets	$ 33,173	$ 38,686