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Loans and the Allowance for Credit Losses - Summary of Commercial Loans by Risk Grade (Detail) - USD ($)
$ in Thousands
Jun. 30, 2026
Dec. 31, 2025
Summary of commercial loans by risk grade    
Portfolio loans, net of unearned income $ 19,478,966 $ 19,226,432
Commercial and Industrial [Member]    
Summary of commercial loans by risk grade    
Portfolio loans, net of unearned income 2,949,863 2,863,893
Commercial and Industrial [Member] | Pass [Member]    
Summary of commercial loans by risk grade    
Portfolio loans, net of unearned income 2,734,095 2,736,863
Commercial and Industrial [Member] | Criticized [Member]    
Summary of commercial loans by risk grade    
Portfolio loans, net of unearned income 142,791 84,552
Commercial and Industrial [Member] | Classified - substandard [Member]    
Summary of commercial loans by risk grade    
Portfolio loans, net of unearned income 72,977 42,478
Commercial Portfolio Segment [Member]    
Summary of commercial loans by risk grade    
Portfolio loans, net of unearned income 14,043,233 13,802,727
Commercial Portfolio Segment [Member] | Pass [Member]    
Summary of commercial loans by risk grade    
Portfolio loans, net of unearned income 13,315,332 13,197,799
Commercial Portfolio Segment [Member] | Criticized [Member]    
Summary of commercial loans by risk grade    
Portfolio loans, net of unearned income 431,234 413,068
Commercial Portfolio Segment [Member] | Classified - substandard [Member]    
Summary of commercial loans by risk grade    
Portfolio loans, net of unearned income 296,667 191,860
Commercial Portfolio Segment [Member] | Commercial Real Estate - Land and Construction [Member]    
Summary of commercial loans by risk grade    
Portfolio loans, net of unearned income 1,505,492 1,783,637
Commercial Portfolio Segment [Member] | Commercial Real Estate - Land and Construction [Member] | Pass [Member]    
Summary of commercial loans by risk grade    
Portfolio loans, net of unearned income 1,452,874 1,748,260
Commercial Portfolio Segment [Member] | Commercial Real Estate - Land and Construction [Member] | Criticized [Member]    
Summary of commercial loans by risk grade    
Portfolio loans, net of unearned income 22,398 8,331
Commercial Portfolio Segment [Member] | Commercial Real Estate - Land and Construction [Member] | Classified - substandard [Member]    
Summary of commercial loans by risk grade    
Portfolio loans, net of unearned income 30,220 27,046
Commercial Portfolio Segment [Member] | Commercial Real Estate - Improved Property [Member]    
Summary of commercial loans by risk grade    
Portfolio loans, net of unearned income 9,587,878 9,155,197
Commercial Portfolio Segment [Member] | Commercial Real Estate - Improved Property [Member] | Pass [Member]    
Summary of commercial loans by risk grade    
Portfolio loans, net of unearned income 9,128,363 8,712,676
Commercial Portfolio Segment [Member] | Commercial Real Estate - Improved Property [Member] | Criticized [Member]    
Summary of commercial loans by risk grade    
Portfolio loans, net of unearned income 266,045 320,185
Commercial Portfolio Segment [Member] | Commercial Real Estate - Improved Property [Member] | Classified - substandard [Member]    
Summary of commercial loans by risk grade    
Portfolio loans, net of unearned income 193,470 122,336
Commercial Portfolio Segment [Member] | Commercial and Industrial [Member]    
Summary of commercial loans by risk grade    
Portfolio loans, net of unearned income 2,949,863 2,863,893
Commercial Portfolio Segment [Member] | Commercial and Industrial [Member] | Pass [Member]    
Summary of commercial loans by risk grade    
Portfolio loans, net of unearned income 2,734,095 2,736,863
Commercial Portfolio Segment [Member] | Commercial and Industrial [Member] | Criticized [Member]    
Summary of commercial loans by risk grade    
Portfolio loans, net of unearned income 142,791 84,552
Commercial Portfolio Segment [Member] | Commercial and Industrial [Member] | Classified - substandard [Member]    
Summary of commercial loans by risk grade    
Portfolio loans, net of unearned income $ 72,977 $ 42,478