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Investment Information - Aging of available for sale securities in an unrealized loss position (Details) - USD ($) $ in Thousands | Sep. 30, 2022 | Dec. 31, 2021
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Debt Securities, Available-for-sale, Unrealized Loss Position, Estimated Fair Value [Abstract] |  |
Estimated Fair Value - Less than 12 Months | $ 14,940,746 | $ 12,238,683
Estimated Fair Value - 12 Months or More | 2,936,029 | 297,357
Estimated Fair Value | 17,876,775 | 12,536,040
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract] |  |
Gross Unrealized Losses - Less than 12 Months | (1,376,623) | (157,279)
Gross Unrealized Losses - 12 Months or More | (485,664) | (14,265)
Gross Unrealized Losses | (1,862,287) | (171,544)
Fixed maturities |  |
Debt Securities, Available-for-sale, Unrealized Loss Position, Estimated Fair Value [Abstract] |  |
Estimated Fair Value - Less than 12 Months | 14,713,545 | 11,953,950
Estimated Fair Value - 12 Months or More | 2,936,029 | 297,357
Estimated Fair Value | 17,649,574 | 12,251,307
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract] |  |
Gross Unrealized Losses - Less than 12 Months | (1,374,990) | (156,689)
Gross Unrealized Losses - 12 Months or More | (485,664) | (14,265)
Gross Unrealized Losses | (1,860,654) | (170,954)
Corporate bonds |  |
Debt Securities, Available-for-sale, Unrealized Loss Position, Estimated Fair Value [Abstract] |  |
Estimated Fair Value - Less than 12 Months | 5,596,229 | 3,639,582
Estimated Fair Value - 12 Months or More | 1,470,800 | 98,867
Estimated Fair Value | 7,067,029 | 3,738,449
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract] |  |
Gross Unrealized Losses - Less than 12 Months | (625,774) | (63,938)
Gross Unrealized Losses - 12 Months or More | (269,591) | (5,256)
Gross Unrealized Losses | (895,365) | (69,194)
Mortgage backed securities |  |
Debt Securities, Available-for-sale, Unrealized Loss Position, Estimated Fair Value [Abstract] |  |
Estimated Fair Value - Less than 12 Months | 620,572 | 222,176
Estimated Fair Value - 12 Months or More | 93,902 | 46,809
Estimated Fair Value | 714,474 | 268,985
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract] |  |
Gross Unrealized Losses - Less than 12 Months | (63,732) | (3,545)
Gross Unrealized Losses - 12 Months or More | (20,451) | (1,865)
Gross Unrealized Losses | (84,183) | (5,410)
Municipal bonds |  |
Debt Securities, Available-for-sale, Unrealized Loss Position, Estimated Fair Value [Abstract] |  |
Estimated Fair Value - Less than 12 Months | 373,219 | 26,665
Estimated Fair Value - 12 Months or More | 9,399 | 16,361
Estimated Fair Value | 382,618 | 43,026
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract] |  |
Gross Unrealized Losses - Less than 12 Months | (36,039) | (385)
Gross Unrealized Losses - 12 Months or More | (1,653) | (1,024)
Gross Unrealized Losses | (37,692) | (1,409)
Commercial mortgage backed securities |  |
Debt Securities, Available-for-sale, Unrealized Loss Position, Estimated Fair Value [Abstract] |  |
Estimated Fair Value - Less than 12 Months | 995,680 | 675,603
Estimated Fair Value - 12 Months or More | 34,445 | 5,908
Estimated Fair Value | 1,030,125 | 681,511
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract] |  |
Gross Unrealized Losses - Less than 12 Months | (49,215) | (2,805)
Gross Unrealized Losses - 12 Months or More | (795) | (312)
Gross Unrealized Losses | (50,010) | (3,117)
US government and government agencies |  |
Debt Securities, Available-for-sale, Unrealized Loss Position, Estimated Fair Value [Abstract] |  |
Estimated Fair Value - Less than 12 Months | 4,205,475 | 4,211,621
Estimated Fair Value - 12 Months or More | 715,347 | 33,373
Estimated Fair Value | 4,920,822 | 4,244,994
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract] |  |
Gross Unrealized Losses - Less than 12 Months | (303,805) | (44,180)
Gross Unrealized Losses - 12 Months or More | (96,979) | (1,787)
Gross Unrealized Losses | (400,784) | (45,967)
Non-US government securities |  |
Debt Securities, Available-for-sale, Unrealized Loss Position, Estimated Fair Value [Abstract] |  |
Estimated Fair Value - Less than 12 Months | 1,728,965 | 1,511,301
Estimated Fair Value - 12 Months or More | 301,298 | 62,957
Estimated Fair Value | 2,030,263 | 1,574,258
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract] |  |
Gross Unrealized Losses - Less than 12 Months | (221,540) | (31,983)
Gross Unrealized Losses - 12 Months or More | (66,043) | (2,766)
Gross Unrealized Losses | (287,583) | (34,749)
Asset backed securities |  |
Debt Securities, Available-for-sale, Unrealized Loss Position, Estimated Fair Value [Abstract] |  |
Estimated Fair Value - Less than 12 Months | 1,193,405 | 1,667,002
Estimated Fair Value - 12 Months or More | 310,838 | 33,082
Estimated Fair Value | 1,504,243 | 1,700,084
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract] |  |
Gross Unrealized Losses - Less than 12 Months | (74,885) | (9,853)
Gross Unrealized Losses - 12 Months or More | (30,152) | (1,255)
Gross Unrealized Losses | (105,037) | (11,108)
Short-term investments |  |
Debt Securities, Available-for-sale, Unrealized Loss Position, Estimated Fair Value [Abstract] |  |
Estimated Fair Value - Less than 12 Months | 227,201 | 284,733
Estimated Fair Value - 12 Months or More | 0 | 0
Estimated Fair Value | 227,201 | 284,733
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract] |  |
Gross Unrealized Losses - Less than 12 Months | (1,633) | (590)
Gross Unrealized Losses - 12 Months or More | 0 | 0
Gross Unrealized Losses | $ (1,633) | $ (590)

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- Definition 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. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 50 -Paragraph 5 -URI https://asc.fasb.org/extlink&oid=124269663&loc=SL82922890-210455 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 7 -URI https://asc.fasb.org/extlink&oid=126970911&loc=d3e27337-111563 Reference 3: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 55 -Paragraph 8 -URI https://asc.fasb.org/extlink&oid=121590138&loc=SL82922954-210456 + Details
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