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Investments - Gross Unrealized Losses and Fair Value for Mortgage-Backed in Unrealized Loss Position (Details) - USD ($) $ in Thousands | Jun. 30, 2024 | Dec. 31, 2023
--- | --- | ---
Less than 12 months |  |
Gross Unrealized Losses | $ (2,897) | $ (2,752)
Estimated Fair Value | 183,669 | 142,116
12 months or more |  |
Gross Unrealized Losses | (145,806) | (150,916)
Estimated Fair Value | 1,802,403 | 2,123,439
Total |  |
Gross Unrealized Losses | (148,703) | (153,668)
Estimated Fair Value | 1,986,072 | 2,265,555
Mortgage-backed securities |  |
Less than 12 months |  |
Gross Unrealized Losses | (1,739) | (531)
Estimated Fair Value | 106,041 | 51,391
12 months or more |  |
Gross Unrealized Losses | (72,217) | (61,949)
Estimated Fair Value | 313,289 | 300,318
Total |  |
Gross Unrealized Losses | (73,956) | (62,480)
Estimated Fair Value | 419,330 | 351,709
Utah Housing Corporation bonds |  |
Less than 12 months |  |
Gross Unrealized Losses | 0 | 0
Estimated Fair Value | 0 | 0
12 months or more |  |
Gross Unrealized Losses | (320) | (279)
Estimated Fair Value | 2,881 | 3,129
Total |  |
Gross Unrealized Losses | (320) | (279)
Estimated Fair Value | 2,881 | 3,129
U.S. government-sponsored enterprises and Treasuries |  |
Less than 12 months |  |
Gross Unrealized Losses | 0 | 0
Estimated Fair Value | 0 | 0
12 months or more |  |
Gross Unrealized Losses | (55,211) | (66,870)
Estimated Fair Value | 1,241,731 | 1,578,739
Total |  |
Gross Unrealized Losses | (55,211) | (66,870)
Estimated Fair Value | 1,241,731 | 1,578,739
Other securities |  |
Less than 12 months |  |
Gross Unrealized Losses | (1,158) | (2,221)
Estimated Fair Value | 77,628 | 90,725
12 months or more |  |
Gross Unrealized Losses | (18,058) | (21,818)
Estimated Fair Value | 244,502 | 241,253
Total |  |
Gross Unrealized Losses | (19,216) | (24,039)
Estimated Fair Value | $ 322,130 | $ 331,978

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