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Investments - Gross Unrealized Losses and Fair Value for Mortgage-Backed in Unrealized Loss Position (Details) - USD ($) $ in Thousands | Mar. 31, 2025 | Dec. 31, 2024
--- | --- | ---
Less than 12 months |  |
Gross Unrealized Losses | $ (907) | $ (2,797)
Estimated Fair Value | 108,396 | 149,164
12 months or more |  |
Gross Unrealized Losses | (99,035) | (115,288)
Estimated Fair Value | 1,075,581 | 1,390,575
Total |  |
Gross Unrealized Losses | (99,942) | (118,085)
Estimated Fair Value | 1,183,977 | 1,539,739
Mortgage-backed securities |  |
Less than 12 months |  |
Gross Unrealized Losses | (846) | (2,723)
Estimated Fair Value | 96,803 | 137,585
12 months or more |  |
Gross Unrealized Losses | (63,774) | (70,512)
Estimated Fair Value | 308,278 | 290,257
Total |  |
Gross Unrealized Losses | (64,620) | (73,235)
Estimated Fair Value | 405,081 | 427,842
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 | (409) | (490)
Estimated Fair Value | 2,250 | 2,359
Total |  |
Gross Unrealized Losses | (409) | (490)
Estimated Fair Value | 2,250 | 2,359
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 | (24,058) | (32,265)
Estimated Fair Value | 624,355 | 915,744
Total |  |
Gross Unrealized Losses | (24,058) | (32,265)
Estimated Fair Value | 624,355 | 915,744
Other securities |  |
Less than 12 months |  |
Gross Unrealized Losses | (61) | (74)
Estimated Fair Value | 11,593 | 11,579
12 months or more |  |
Gross Unrealized Losses | (10,794) | (12,021)
Estimated Fair Value | 140,698 | 182,215
Total |  |
Gross Unrealized Losses | (10,855) | (12,095)
Estimated Fair Value | $ 152,291 | $ 193,794

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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/exampleRef -Topic 326 -SubTopic 30 -Name Accounting Standards Codification -Section 55 -Paragraph 8 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479081/326-30-55-8 Reference 2: http://fasb.org/us-gaap/role/ref/otherTransitionRef -Topic 320 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 7 -Publisher FASB -URI https://asc.fasb.org/1943274/2147481800/320-10-50-7 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 5 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479106/326-30-50-5 + Details
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