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Investment Information - Aging of available for sale securities in an unrealized loss position (Details) - USD ($) $ in Thousands | Jun. 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 | $ 16,180,106 | $ 12,238,683
Estimated Fair Value - 12 Months or More | 869,409 | 297,357
Estimated Fair Value | 17,049,515 | 12,536,040
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract] |  |
Gross Unrealized Losses - Less than 12 Months | (1,145,737) | (157,279)
Gross Unrealized Losses - 12 Months or More | (112,851) | (14,265)
Gross Unrealized Losses | (1,258,588) | (171,544)
Fixed maturities |  |
Debt Securities, Available-for-sale, Unrealized Loss Position, Estimated Fair Value [Abstract] |  |
Estimated Fair Value - Less than 12 Months | 15,674,308 | 11,953,950
Estimated Fair Value - 12 Months or More | 869,409 | 297,357
Estimated Fair Value | 16,543,717 | 12,251,307
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract] |  |
Gross Unrealized Losses - Less than 12 Months | (1,144,480) | (156,689)
Gross Unrealized Losses - 12 Months or More | (112,851) | (14,265)
Gross Unrealized Losses | (1,257,331) | (170,954)
Fixed maturities | Corporate bonds |  |
Debt Securities, Available-for-sale, Unrealized Loss Position, Estimated Fair Value [Abstract] |  |
Estimated Fair Value - Less than 12 Months | 6,583,215 | 3,639,582
Estimated Fair Value - 12 Months or More | 489,098 | 98,867
Estimated Fair Value | 7,072,313 | 3,738,449
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract] |  |
Gross Unrealized Losses - Less than 12 Months | (580,235) | (63,938)
Gross Unrealized Losses - 12 Months or More | (75,429) | (5,256)
Gross Unrealized Losses | (655,664) | (69,194)
Fixed maturities | Mortgage backed securities |  |
Debt Securities, Available-for-sale, Unrealized Loss Position, Estimated Fair Value [Abstract] |  |
Estimated Fair Value - Less than 12 Months | 595,485 | 222,176
Estimated Fair Value - 12 Months or More | 61,751 | 46,809
Estimated Fair Value | 657,236 | 268,985
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract] |  |
Gross Unrealized Losses - Less than 12 Months | (46,415) | (3,545)
Gross Unrealized Losses - 12 Months or More | (9,483) | (1,865)
Gross Unrealized Losses | (55,898) | (5,410)
Fixed maturities | Municipal bonds |  |
Debt Securities, Available-for-sale, Unrealized Loss Position, Estimated Fair Value [Abstract] |  |
Estimated Fair Value - Less than 12 Months | 271,481 | 26,665
Estimated Fair Value - 12 Months or More | 8,876 | 16,361
Estimated Fair Value | 280,357 | 43,026
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract] |  |
Gross Unrealized Losses - Less than 12 Months | (17,908) | (385)
Gross Unrealized Losses - 12 Months or More | (1,028) | (1,024)
Gross Unrealized Losses | (18,936) | (1,409)
Fixed maturities | Commercial mortgage backed securities |  |
Debt Securities, Available-for-sale, Unrealized Loss Position, Estimated Fair Value [Abstract] |  |
Estimated Fair Value - Less than 12 Months | 973,212 | 675,603
Estimated Fair Value - 12 Months or More | 0 | 5,908
Estimated Fair Value | 973,212 | 681,511
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract] |  |
Gross Unrealized Losses - Less than 12 Months | (42,056) | (2,805)
Gross Unrealized Losses - 12 Months or More | 0 | (312)
Gross Unrealized Losses | (42,056) | (3,117)
Fixed maturities | US government and government agencies |  |
Debt Securities, Available-for-sale, Unrealized Loss Position, Estimated Fair Value [Abstract] |  |
Estimated Fair Value - Less than 12 Months | 4,029,550 | 4,211,621
Estimated Fair Value - 12 Months or More | 69,596 | 33,373
Estimated Fair Value | 4,099,146 | 4,244,994
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract] |  |
Gross Unrealized Losses - Less than 12 Months | (235,510) | (44,180)
Gross Unrealized Losses - 12 Months or More | (5,276) | (1,787)
Gross Unrealized Losses | (240,786) | (45,967)
Fixed maturities | Non-US government securities |  |
Debt Securities, Available-for-sale, Unrealized Loss Position, Estimated Fair Value [Abstract] |  |
Estimated Fair Value - Less than 12 Months | 1,929,278 | 1,511,301
Estimated Fair Value - 12 Months or More | 103,969 | 62,957
Estimated Fair Value | 2,033,247 | 1,574,258
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract] |  |
Gross Unrealized Losses - Less than 12 Months | (148,781) | (31,983)
Gross Unrealized Losses - 12 Months or More | (14,943) | (2,766)
Gross Unrealized Losses | (163,724) | (34,749)
Fixed maturities | Asset backed securities |  |
Debt Securities, Available-for-sale, Unrealized Loss Position, Estimated Fair Value [Abstract] |  |
Estimated Fair Value - Less than 12 Months | 1,292,087 | 1,667,002
Estimated Fair Value - 12 Months or More | 136,119 | 33,082
Estimated Fair Value | 1,428,206 | 1,700,084
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract] |  |
Gross Unrealized Losses - Less than 12 Months | (73,575) | (9,853)
Gross Unrealized Losses - 12 Months or More | (6,692) | (1,255)
Gross Unrealized Losses | (80,267) | (11,108)
Short-term investments |  |
Debt Securities, Available-for-sale, Unrealized Loss Position, Estimated Fair Value [Abstract] |  |
Estimated Fair Value - Less than 12 Months | 505,798 | 284,733
Estimated Fair Value - 12 Months or More | 0 | 0
Estimated Fair Value | 505,798 | 284,733
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract] |  |
Gross Unrealized Losses - Less than 12 Months | (1,257) | (590)
Gross Unrealized Losses - 12 Months or More | 0 | 0
Gross Unrealized Losses | $ (1,257) | $ (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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