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Business Combination - Schedule of Pro Forma Information (Details) - Luther Burbank - USD ($) $ in Thousands | 9 Months Ended
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Jun. 30, 2024 | Jun. 30, 2023
Business Acquisition [Line Items] |  |
Net-interest income | $ 531,398 | $ 646,731
Non-interest income | 47,493 | 40,965
Net income | $ 142,921 | $ 238,473

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