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Investments - Gross Unrealized Losses and Fair Value for Mortgage-Backed in Unrealized Loss Position (Details) - USD ($) $ in Thousands | Mar. 31, 2023 | Dec. 31, 2022
--- | --- | ---
Less than 12 months |  |
Gross Unrealized Losses | $ (14,052) | $ (58,293)
Estimated Fair Value | 372,448 | 1,024,671
12 months or more |  |
Gross Unrealized Losses | (163,031) | (153,985)
Estimated Fair Value | 1,901,108 | 1,313,469
Total |  |
Gross Unrealized Losses | (177,083) | (212,278)
Estimated Fair Value | 2,273,556 | 2,338,140
Mortgage-backed securities |  |
Less than 12 months |  |
Gross Unrealized Losses | (1,138) | (13,956)
Estimated Fair Value | 22,201 | 99,598
12 months or more |  |
Gross Unrealized Losses | (60,748) | (54,749)
Estimated Fair Value | 297,543 | 220,576
Total |  |
Gross Unrealized Losses | (61,886) | (68,705)
Estimated Fair Value | 319,744 | 320,174
Utah Housing Corporation bonds |  |
Less than 12 months |  |
Gross Unrealized Losses | 0 | (357)
Estimated Fair Value | 0 | 3,227
12 months or more |  |
Gross Unrealized Losses | (294) | 0
Estimated Fair Value | 3,166 | 0
Total |  |
Gross Unrealized Losses | (294) | (357)
Estimated Fair Value | 3,166 | 3,227
U.S. government-sponsored enterprises and Treasuries |  |
Less than 12 months |  |
Gross Unrealized Losses | (4,463) | (28,128)
Estimated Fair Value | 193,623 | 689,300
12 months or more |  |
Gross Unrealized Losses | (88,085) | (87,288)
Estimated Fair Value | 1,471,861 | 1,000,010
Total |  |
Gross Unrealized Losses | (92,548) | (115,416)
Estimated Fair Value | 1,665,484 | 1,689,310
Other securities |  |
Less than 12 months |  |
Gross Unrealized Losses | (8,451) | (15,852)
Estimated Fair Value | 156,624 | 232,546
12 months or more |  |
Gross Unrealized Losses | (13,904) | (11,948)
Estimated Fair Value | 128,538 | 92,883
Total |  |
Gross Unrealized Losses | (22,355) | (27,800)
Estimated Fair Value | $ 285,162 | $ 325,429

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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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- Definition 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. + References Reference 1: 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 2: 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 + Details
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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 less 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 320 -SubTopic 10 -Section 50 -Paragraph 7 -URI https://asc.fasb.org/extlink&oid=126970911&loc=d3e27337-111563 Reference 2: 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 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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