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Investments - Gross Unrealized Losses and Fair Value for Mortgage-Backed in Unrealized Loss Position (Details) - USD ($) $ in Thousands | Jun. 30, 2023 | Dec. 31, 2022
--- | --- | ---
Less than 12 months |  |
Gross Unrealized Losses | $ (9,419) | $ (58,293)
Estimated Fair Value | 334,073 | 1,024,671
12 months or more |  |
Gross Unrealized Losses | (181,681) | (153,985)
Estimated Fair Value | 1,984,434 | 1,313,469
Total |  |
Gross Unrealized Losses | (191,100) | (212,278)
Estimated Fair Value | 2,318,507 | 2,338,140
Mortgage-backed securities |  |
Less than 12 months |  |
Gross Unrealized Losses | (879) | (13,956)
Estimated Fair Value | 44,532 | 99,598
12 months or more |  |
Gross Unrealized Losses | (65,461) | (54,749)
Estimated Fair Value | 308,309 | 220,576
Total |  |
Gross Unrealized Losses | (66,340) | (68,705)
Estimated Fair Value | 352,841 | 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 | (405) | 0
Estimated Fair Value | 3,055 | 0
Total |  |
Gross Unrealized Losses | (405) | (357)
Estimated Fair Value | 3,055 | 3,227
U.S. government-sponsored enterprises and Treasuries |  |
Less than 12 months |  |
Gross Unrealized Losses | (4,419) | (28,128)
Estimated Fair Value | 93,990 | 689,300
12 months or more |  |
Gross Unrealized Losses | (98,663) | (87,288)
Estimated Fair Value | 1,511,818 | 1,000,010
Total |  |
Gross Unrealized Losses | (103,082) | (115,416)
Estimated Fair Value | 1,605,808 | 1,689,310
Other securities |  |
Less than 12 months |  |
Gross Unrealized Losses | (4,121) | (15,852)
Estimated Fair Value | 195,551 | 232,546
12 months or more |  |
Gross Unrealized Losses | (17,152) | (11,948)
Estimated Fair Value | 161,252 | 92,883
Total |  |
Gross Unrealized Losses | (21,273) | (27,800)
Estimated Fair Value | $ 356,803 | $ 325,429

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