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Debt Securities - Debt securities in an unrealized loss position (Details) - USD ($) $ in Thousands | Mar. 31, 2023 | Dec. 31, 2022
--- | --- | ---
Fair Value |  |
Less than 12 months | $ 237,884 | $ 1,070,674
12 months or more | 2,102,068 | 1,368,859
Total | 2,339,952 | 2,439,533
Unrealized Losses |  |
Less than 12 months | (8,637) | (81,841)
Unrealized Losses | (271,946) | (229,363)
Total | (280,583) | (311,204)
Fair Value |  |
Less than 12 months |  | 58,065
12 months or more | 780,653 | 727,230
Total | 780,653 | 785,295
Unrealized Losses |  |
Less than 12 months |  | (8,009)
12 months or more | (126,906) | (125,008)
Total | (126,906) | (133,017)
U.S. Treasury securities |  |
Fair Value |  |
Less than 12 months | 964 | 74
12 months or more | 83,668 | 113,987
Total | 84,632 | 114,061
Unrealized Losses |  |
Less than 12 months | (32) | 0
Unrealized Losses | (2,518) | (3,744)
Total | (2,550) | (3,744)
Obligations of U.S. government corporations and agencies |  |
Fair Value |  |
Less than 12 months | 11,262 | 19,603
12 months or more | 196 | 0
Total | 11,458 | 19,603
Unrealized Losses |  |
Less than 12 months | (223) | (321)
Unrealized Losses | (8) | 0
Total | (231) | (321)
Obligations of states and political subdivisions |  |
Fair Value |  |
Less than 12 months | 80,541 | 166,147
12 months or more | 133,343 | 75,217
Total | 213,884 | 241,364
Unrealized Losses |  |
Less than 12 months | (755) | (10,059)
Unrealized Losses | (20,035) | (16,016)
Total | (20,790) | (26,075)
Asset-backed securities |  |
Fair Value |  |
Less than 12 months | 16,954 | 390,164
12 months or more | 452,193 | 79,711
Total | 469,147 | 469,875
Unrealized Losses |  |
Less than 12 months | (346) | (15,648)
Unrealized Losses | (18,741) | (4,035)
Total | (19,087) | (19,683)
Commercial mortgage-backed securities |  |
Fair Value |  |
Less than 12 months | 7,634 | 89,428
12 months or more | 101,193 | 18,966
Total | 108,827 | 108,394
Unrealized Losses |  |
Less than 12 months | (290) | (12,623)
Unrealized Losses | (14,603) | (3,406)
Total | (14,893) | (16,029)
Fair Value |  |
Less than 12 months |  | 58,065
12 months or more | 406,940 | 353,017
Total | 406,940 | 411,082
Unrealized Losses |  |
Less than 12 months |  | (8,009)
12 months or more | (63,198) | (55,729)
Total | (63,198) | (63,738)
Residential mortgage-backed securities |  |
Fair Value |  |
Less than 12 months | 103,167 | 366,221
12 months or more | 1,122,195 | 876,668
Total | 1,225,362 | 1,242,889
Unrealized Losses |  |
Less than 12 months | (5,778) | (38,111)
Unrealized Losses | (194,821) | (182,606)
Total | (200,599) | (220,717)
Fair Value |  |
Less than 12 months |  | 0
12 months or more | 373,713 | 374,213
Total | 373,713 | 374,213
Unrealized Losses |  |
Less than 12 months |  | 0
12 months or more | (63,708) | (69,279)
Total | (63,708) | (69,279)
Corporate debt securities |  |
Fair Value |  |
Less than 12 months | 17,362 | 39,037
12 months or more | 209,280 | 204,310
Total | 226,642 | 243,347
Unrealized Losses |  |
Less than 12 months | (1,213) | (5,079)
Unrealized Losses | (21,220) | (19,556)
Total | $ (22,433) | $ (24,635)

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