Loans and the Allowance for Credit Losses - Summary of Commercial Loans by Risk Grade (Detail) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Summary of commercial loans by risk grade
Portfolio loans, net of unearned income	$ 11,873,167	$ 11,638,461
Commercial and Industrial [Member]
Summary of commercial loans by risk grade
Portfolio loans, net of unearned income	1,683,172	1,670,659
Commercial and Industrial [Member] | Pass [Member]
Summary of commercial loans by risk grade
Portfolio loans, net of unearned income	1,588,033	1,586,683
Commercial and Industrial [Member] | Criticized [Member]
Summary of commercial loans by risk grade
Portfolio loans, net of unearned income	65,431	73,204
Commercial and Industrial [Member] | Classified - substandard [Member]
Summary of commercial loans by risk grade
Portfolio loans, net of unearned income	29,708	10,772
Commercial Portfolio Segment [Member]
Summary of commercial loans by risk grade
Portfolio loans, net of unearned income	8,438,105	8,236,107
Commercial Portfolio Segment [Member] | Pass [Member]
Summary of commercial loans by risk grade
Portfolio loans, net of unearned income	8,164,671	7,977,436
Commercial Portfolio Segment [Member] | Criticized [Member]
Summary of commercial loans by risk grade
Portfolio loans, net of unearned income	171,536	183,174
Commercial Portfolio Segment [Member] | Classified - substandard [Member]
Summary of commercial loans by risk grade
Portfolio loans, net of unearned income	101,898	75,497
Commercial Portfolio Segment [Member] | Commercial Real Estate - Land and Construction [Member]
Summary of commercial loans by risk grade
Portfolio loans, net of unearned income	1,087,649	1,055,865
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	1,084,975	1,053,359
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	2,457	2,497
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	217	9
Commercial Portfolio Segment [Member] | Commercial Real Estate - Improved Property [Member]
Summary of commercial loans by risk grade
Portfolio loans, net of unearned income	5,667,284	5,509,583
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	5,491,663	5,337,394
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	103,648	107,473
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	71,973	64,716
Commercial Portfolio Segment [Member] | Commercial and Industrial [Member]
Summary of commercial loans by risk grade
Portfolio loans, net of unearned income	1,683,172	1,670,659
Commercial Portfolio Segment [Member] | Commercial and Industrial [Member] | Pass [Member]
Summary of commercial loans by risk grade
Portfolio loans, net of unearned income	1,588,033	1,586,683
Commercial Portfolio Segment [Member] | Commercial and Industrial [Member] | Criticized [Member]
Summary of commercial loans by risk grade
Portfolio loans, net of unearned income	65,431	73,204
Commercial Portfolio Segment [Member] | Commercial and Industrial [Member] | Classified - substandard [Member]
Summary of commercial loans by risk grade
Portfolio loans, net of unearned income	$ 29,708	$ 10,772