v3.26.1
Comprehensive Income - Components of Accumulated Other Comprehensive Income (Detail) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Jun. 30, 2026
Mar. 31, 2026
Jun. 30, 2025
Mar. 31, 2025
Jun. 30, 2026
Jun. 30, 2025
Accumulated Other Comprehensive Income (Loss) [Line Items]            
Beginning Balance $ 5,488,126 $ 5,495,983 $ 5,314,449 $ 4,993,223 $ 5,495,983 $ 4,993,223
Total change in other comprehensive income (loss), net of tax 5,748 (10,188) 11,280 28,895 (4,440) 40,175
Ending Balance 5,510,537 5,488,126 5,364,541 5,314,449 5,510,537 5,364,541
Defined Benefit Pension Item [Member]            
Accumulated Other Comprehensive Income (Loss) [Line Items]            
Beginning Balance   (4,198)     (4,198)  
Other comprehensive (loss) income before reclassification         0  
Amounts reclassified from accumulated other comprehensive income         0  
Total change in other comprehensive income (loss), net of tax         0  
Ending Balance (4,198)       (4,198)  
Unrealized Gains/Losses on AFS Securities [Member]            
Accumulated Other Comprehensive Income (Loss) [Line Items]            
Beginning Balance   (158,498)     (158,498)  
Other comprehensive (loss) income before reclassification         (12,398)  
Amounts reclassified from accumulated other comprehensive income         7,403  
Total change in other comprehensive income (loss), net of tax         (4,995)  
Ending Balance (163,493)       (163,493)  
Accumulated Other Comprehensive Income (Loss) [Member]            
Accumulated Other Comprehensive Income (Loss) [Line Items]            
Beginning Balance (149,115) (138,927) (195,008) (223,903) (138,927) (223,903)
Other comprehensive (loss) income before reclassification         (8,772)  
Amounts reclassified from accumulated other comprehensive income         4,332  
Total change in other comprehensive income (loss), net of tax 5,748 (10,188) 11,280 28,895 (4,440)  
Ending Balance (143,367) (149,115) $ (183,728) $ (195,008) (143,367) $ (183,728)
Unrealized Gains/Losses on Cash Flow Hedges [Member]            
Accumulated Other Comprehensive Income (Loss) [Line Items]            
Beginning Balance   $ 23,769     23,769  
Other comprehensive (loss) income before reclassification         3,626  
Amounts reclassified from accumulated other comprehensive income         (3,071)  
Total change in other comprehensive income (loss), net of tax         555  
Ending Balance $ 24,324       $ 24,324