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Investment Securities - Schedule of Available-for-sale Investment Securities Portfolios (Details) - USD ($) | Sep. 30, 2023 | Dec. 31, 2022 | Sep. 30, 2022
--- | --- | --- | ---
Available-for-sale securities |  |  |
Continuous unrealized losses existing for less than 12 months, fair value | $ 1,078,576,000 |  |
Continuous unrealized losses existing for less than 12 months, unrealized losses | (41,403,000) |  |
Continuous unrealized losses existing for greater than 12 months, fair value | 2,521,891,000 |  |
Continuous unrealized losses existing for greater than 12 months, unrealized losses | (662,535,000) |  |
Total, fair value | 3,600,467,000 |  |
Total, unrealized losses | (703,938,000) |  |
Available-for-sale securities, at fair value | 3,611,835,000 | $ 3,243,017,000 | $ 2,923,653,000
U.S. government agencies |  |  |
Available-for-sale securities |  |  |
Continuous unrealized losses existing for less than 12 months, fair value | 29,974,000 |  |
Continuous unrealized losses existing for less than 12 months, unrealized losses | (26,000) |  |
Continuous unrealized losses existing for greater than 12 months, fair value | 42,456,000 |  |
Continuous unrealized losses existing for greater than 12 months, unrealized losses | (7,544,000) |  |
Total, fair value | 72,430,000 |  |
Total, unrealized losses | (7,570,000) |  |
Available-for-sale securities, at fair value | 72,430,000 | 74,222,000 | 44,013,000
Municipal |  |  |
Available-for-sale securities |  |  |
Continuous unrealized losses existing for less than 12 months, fair value | 71,452,000 |  |
Continuous unrealized losses existing for less than 12 months, unrealized losses | (2,331,000) |  |
Continuous unrealized losses existing for greater than 12 months, fair value | 90,634,000 |  |
Continuous unrealized losses existing for greater than 12 months, unrealized losses | (6,403,000) |  |
Total, fair value | 162,086,000 |  |
Total, unrealized losses | (8,734,000) |  |
Available-for-sale securities, at fair value | 168,523,000 | 168,655,000 | 174,001,000
Financial issuers |  |  |
Available-for-sale securities |  |  |
Continuous unrealized losses existing for less than 12 months, fair value | 0 |  |
Continuous unrealized losses existing for less than 12 months, unrealized losses | 0 |  |
Continuous unrealized losses existing for greater than 12 months, fair value | 75,627,000 |  |
Continuous unrealized losses existing for greater than 12 months, unrealized losses | (8,368,000) |  |
Total, fair value | 75,627,000 |  |
Total, unrealized losses | (8,368,000) |  |
Available-for-sale securities, at fair value | 75,627,000 | 84,703,000 | 86,043,000
Other |  |  |
Available-for-sale securities |  |  |
Continuous unrealized losses existing for less than 12 months, fair value | 979,000 |  |
Continuous unrealized losses existing for less than 12 months, unrealized losses | (21,000) |  |
Continuous unrealized losses existing for greater than 12 months, fair value | 0 |  |
Continuous unrealized losses existing for greater than 12 months, unrealized losses | 0 |  |
Total, fair value | 979,000 |  |
Total, unrealized losses | (21,000) |  |
Available-for-sale securities, at fair value | 979,000 | 1,002,000 | 990,000
Residential mortgage-backed securities |  |  |
Available-for-sale securities |  |  |
Continuous unrealized losses existing for less than 12 months, fair value | 963,794,000 |  |
Continuous unrealized losses existing for less than 12 months, unrealized losses | (38,223,000) |  |
Continuous unrealized losses existing for greater than 12 months, fair value | 2,242,942,000 |  |
Continuous unrealized losses existing for greater than 12 months, unrealized losses | (617,912,000) |  |
Total, fair value | 3,206,736,000 |  |
Total, unrealized losses | (656,135,000) |  |
Available-for-sale securities, at fair value | 3,206,736,000 | 2,819,937,000 | 2,538,800,000
Commercial (multi-family) mortgage-backed securities |  |  |
Available-for-sale securities |  |  |
Continuous unrealized losses existing for less than 12 months, fair value | 12,377,000 |  |
Continuous unrealized losses existing for less than 12 months, unrealized losses | (802,000) |  |
Continuous unrealized losses existing for greater than 12 months, fair value | 0 |  |
Continuous unrealized losses existing for greater than 12 months, unrealized losses | 0 |  |
Total, fair value | 12,377,000 |  |
Total, unrealized losses | (802,000) |  |
Available-for-sale securities, at fair value | 12,377,000 |  |
Collateralized mortgage obligations |  |  |
Available-for-sale securities |  |  |
Continuous unrealized losses existing for less than 12 months, fair value | 0 |  |
Continuous unrealized losses existing for less than 12 months, unrealized losses | 0 |  |
Continuous unrealized losses existing for greater than 12 months, fair value | 70,232,000 |  |
Continuous unrealized losses existing for greater than 12 months, unrealized losses | (22,308,000) |  |
Total, fair value | 70,232,000 |  |
Total, unrealized losses | (22,308,000) |  |
Available-for-sale securities, at fair value | 70,232,000 | 79,550,000 | 79,806,000
Mortgage-backed securities, subprime |  |  |
Available-for-sale securities |  |  |
Available-for-sale securities, at fair value | $ 0 | $ 0 | $ 0

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