Fixed Maturity Securities In An Unrealized Loss Position (Securities in an Unrealized Loss Position) (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Debt securities
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 Months	$ 12,344,077	$ 8,723,575
Gross Unrealized Losses, Less than 12 Months	813,393	81,947
Fair Value, 12 Months or Greater	3,703,323	361,235
Gross Unrealized Losses, 12 Months or Greater	404,571	42,266
Fair Value, Total	16,047,400	9,084,810
Gross Unrealized Losses, Total	1,217,964	124,213
U.S. government and government agency
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 Months	578,877	487,712
Gross Unrealized Losses, Less than 12 Months	63,917	4,026
Fair Value, 12 Months or Greater	75,024	17,021
Gross Unrealized Losses, 12 Months or Greater	4,890	268
Fair Value, Total	653,901	504,733
Gross Unrealized Losses, Total	68,807	4,294
State and municipal
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 Months	2,158,379	502,333
Gross Unrealized Losses, Less than 12 Months	139,486	7,403
Fair Value, 12 Months or Greater	268,007	29,547
Gross Unrealized Losses, 12 Months or Greater	45,134	2,156
Fair Value, Total	2,426,386	531,880
Gross Unrealized Losses, Total	184,620	9,559
Mortgage-backed
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 Months	1,260,172	558,751
Gross Unrealized Losses, Less than 12 Months	117,781	6,900
Fair Value, 12 Months or Greater	278,990	106,130
Gross Unrealized Losses, 12 Months or Greater	62,897	4,762
Fair Value, Total	1,539,162	664,881
Gross Unrealized Losses, Total	180,678	11,662
Asset-backed
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 Months	2,416,683	3,832,944
Gross Unrealized Losses, Less than 12 Months	97,758	18,503
Fair Value, 12 Months or Greater	1,595,161	75,385
Gross Unrealized Losses, 12 Months or Greater	63,716	291
Fair Value, Total	4,011,844	3,908,329
Gross Unrealized Losses, Total	161,474	18,794
Corporate
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 Months	4,933,243	2,582,860
Gross Unrealized Losses, Less than 12 Months	314,122	29,322
Fair Value, 12 Months or Greater	1,126,858	51,095
Gross Unrealized Losses, 12 Months or Greater	159,576	3,088
Fair Value, Total	6,060,101	2,633,955
Gross Unrealized Losses, Total	473,698	32,410
Foreign government
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 Months	996,723	758,975
Gross Unrealized Losses, Less than 12 Months	80,329	15,793
Fair Value, 12 Months or Greater	359,283	82,057
Gross Unrealized Losses, 12 Months or Greater	68,358	31,701
Fair Value, Total	1,356,006	841,032
Gross Unrealized Losses, Total	$ 148,687	$ 47,494

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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Amount of accumulated unrealized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for 12 months or longer, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in unrealized loss position without allowance for credit loss.

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