Fixed Maturity Securities In An Unrealized Loss Position (Securities in an Unrealized Loss Position) (Details) - USD ($) $ in Thousands	Jun. 30, 2025	Dec. 31, 2024
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 Months	$ 3,129,765	$ 5,460,931
Gross Unrealized Losses, Less than 12 Months	33,678	82,882
Fair Value, 12 Months or Greater	5,697,092	7,086,937
Gross Unrealized Losses, 12 Months or Greater	487,982	625,846
Fair Value, Total	8,826,857	12,547,868
Gross Unrealized Losses, Total	521,660	708,728
U.S. government and government agency
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 Months	941,906	767,515
Gross Unrealized Losses, Less than 12 Months	11,134	9,637
Fair Value, 12 Months or Greater	466,439	560,260
Gross Unrealized Losses, 12 Months or Greater	19,315	33,226
Fair Value, Total	1,408,345	1,327,775
Gross Unrealized Losses, Total	30,449	42,863
State and municipal
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 Months	200,033	348,116
Gross Unrealized Losses, Less than 12 Months	3,908	8,027
Fair Value, 12 Months or Greater	1,262,830	1,411,761
Gross Unrealized Losses, 12 Months or Greater	51,312	81,430
Fair Value, Total	1,462,863	1,759,877
Gross Unrealized Losses, Total	55,220	89,457
Mortgage-backed
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 Months	859,569	1,541,464
Gross Unrealized Losses, Less than 12 Months	11,556	21,326
Fair Value, 12 Months or Greater	887,676	1,060,823
Gross Unrealized Losses, 12 Months or Greater	146,042	171,734
Fair Value, Total	1,747,245	2,602,287
Gross Unrealized Losses, Total	157,598	193,060
Asset-backed
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 Months	610,864	411,763
Gross Unrealized Losses, Less than 12 Months	2,675	4,613
Fair Value, 12 Months or Greater	532,828	626,237
Gross Unrealized Losses, 12 Months or Greater	24,130	36,899
Fair Value, Total	1,143,692	1,038,000
Gross Unrealized Losses, Total	26,805	41,512
Corporate
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 Months	366,889	1,791,970
Gross Unrealized Losses, Less than 12 Months	2,120	21,346
Fair Value, 12 Months or Greater	2,207,465	2,951,377
Gross Unrealized Losses, 12 Months or Greater	83,962	135,117
Fair Value, Total	2,574,354	4,743,347
Gross Unrealized Losses, Total	86,082	156,463
Foreign government
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 Months	150,504	600,103
Gross Unrealized Losses, Less than 12 Months	2,285	17,933
Fair Value, 12 Months or Greater	339,854	476,479
Gross Unrealized Losses, 12 Months or Greater	163,221	167,440
Fair Value, Total	490,358	1,076,582
Gross Unrealized Losses, Total	$ 165,506	$ 185,373