Fixed Maturity Securities In An Unrealized Loss Position (Securities in an Unrealized Loss Position) (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Debt securities
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 Months	$ 13,439,725	$ 8,723,575
Gross Unrealized Losses, Less than 12 Months	691,914	81,947
Fair Value, 12 Months or Greater	1,186,365	361,235
Gross Unrealized Losses, 12 Months or Greater	148,291	42,266
Fair Value, Total	14,626,090	9,084,810
Gross Unrealized Losses, Total	840,205	124,213
U.S. government and government agency
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 Months	570,441	487,712
Gross Unrealized Losses, Less than 12 Months	40,355	4,026
Fair Value, 12 Months or Greater	35,683	17,021
Gross Unrealized Losses, 12 Months or Greater	2,559	268
Fair Value, Total	606,124	504,733
Gross Unrealized Losses, Total	42,914	4,294
State and municipal
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 Months	1,789,266	502,333
Gross Unrealized Losses, Less than 12 Months	92,972	7,403
Fair Value, 12 Months or Greater	95,746	29,547
Gross Unrealized Losses, 12 Months or Greater	12,315	2,156
Fair Value, Total	1,885,012	531,880
Gross Unrealized Losses, Total	105,287	9,559
Mortgage-backed
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 Months	1,223,393	558,751
Gross Unrealized Losses, Less than 12 Months	97,556	6,900
Fair Value, 12 Months or Greater	116,005	106,130
Gross Unrealized Losses, 12 Months or Greater	21,263	4,762
Fair Value, Total	1,339,398	664,881
Gross Unrealized Losses, Total	118,819	11,662
Asset-backed
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 Months	3,788,329	3,832,944
Gross Unrealized Losses, Less than 12 Months	124,135	18,503
Fair Value, 12 Months or Greater	193,620	75,385
Gross Unrealized Losses, 12 Months or Greater	5,414	291
Fair Value, Total	3,981,949	3,908,329
Gross Unrealized Losses, Total	129,549	18,794
Corporate
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 Months	4,775,827	2,582,860
Gross Unrealized Losses, Less than 12 Months	277,520	29,322
Fair Value, 12 Months or Greater	499,270	51,095
Gross Unrealized Losses, 12 Months or Greater	54,373	3,088
Fair Value, Total	5,275,097	2,633,955
Gross Unrealized Losses, Total	331,893	32,410
Foreign government
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 Months	1,292,469	758,975
Gross Unrealized Losses, Less than 12 Months	59,376	15,793
Fair Value, 12 Months or Greater	246,041	82,057
Gross Unrealized Losses, 12 Months or Greater	52,367	31,701
Fair Value, Total	1,538,510	841,032
Gross Unrealized Losses, Total	$ 111,743	$ 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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Amount of accumulated unrealized loss on investment in debt security measured at amortized cost (held-to-maturity), in continuous loss position for less than 12 months.

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