Credit Quality - Schedule of Age Analysis of its Past Due Loans, Segregated by Class of Loans (Detail) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Disclosure Details Of Troubled Debt Restructuring Loan Modification Based On Post Modification Outstanding Balance [Line Items]
Total Financing Receivables	$ 18,994,125	$ 18,051,307
Loans, Recorded Investment >90 Days & Accruing	19,605	18,981
30-89 Days Past Due [Member]
Disclosure Details Of Troubled Debt Restructuring Loan Modification Based On Post Modification Outstanding Balance [Line Items]
Loans, Past Due	112,812	78,208
90 Days or more Past Due [Member]
Disclosure Details Of Troubled Debt Restructuring Loan Modification Based On Post Modification Outstanding Balance [Line Items]
Loans, Past Due	59,289	77,430
Total Past Due [Member]
Disclosure Details Of Troubled Debt Restructuring Loan Modification Based On Post Modification Outstanding Balance [Line Items]
Loans, Past Due	172,101	155,638
Current & Other [Member]
Disclosure Details Of Troubled Debt Restructuring Loan Modification Based On Post Modification Outstanding Balance [Line Items]
Loans, Past Due	18,822,024	17,895,669
Construction & Land Development [Member]
Disclosure Details Of Troubled Debt Restructuring Loan Modification Based On Post Modification Outstanding Balance [Line Items]
Total Financing Receivables	2,395,284	2,014,165
Loans, Recorded Investment >90 Days & Accruing	0	383
Construction & Land Development [Member] | 30-89 Days Past Due [Member]
Disclosure Details Of Troubled Debt Restructuring Loan Modification Based On Post Modification Outstanding Balance [Line Items]
Loans, Past Due	5,121	6,599
Construction & Land Development [Member] | 90 Days or more Past Due [Member]
Disclosure Details Of Troubled Debt Restructuring Loan Modification Based On Post Modification Outstanding Balance [Line Items]
Loans, Past Due	655	3,096
Construction & Land Development [Member] | Total Past Due [Member]
Disclosure Details Of Troubled Debt Restructuring Loan Modification Based On Post Modification Outstanding Balance [Line Items]
Loans, Past Due	5,776	9,695
Construction & Land Development [Member] | Current & Other [Member]
Disclosure Details Of Troubled Debt Restructuring Loan Modification Based On Post Modification Outstanding Balance [Line Items]
Loans, Past Due	2,389,508	2,004,470
Commercial Real Estate [Member] | Owner-Occupied [Member]
Disclosure Details Of Troubled Debt Restructuring Loan Modification Based On Post Modification Outstanding Balance [Line Items]
Total Financing Receivables	1,713,972	1,733,176
Loans, Recorded Investment >90 Days & Accruing	2,873	611
Commercial Real Estate [Member] | Owner-Occupied [Member] | 30-89 Days Past Due [Member]
Disclosure Details Of Troubled Debt Restructuring Loan Modification Based On Post Modification Outstanding Balance [Line Items]
Loans, Past Due	6,491	7,522
Commercial Real Estate [Member] | Owner-Occupied [Member] | 90 Days or more Past Due [Member]
Disclosure Details Of Troubled Debt Restructuring Loan Modification Based On Post Modification Outstanding Balance [Line Items]
Loans, Past Due	11,264	13,325
Commercial Real Estate [Member] | Owner-Occupied [Member] | Total Past Due [Member]
Disclosure Details Of Troubled Debt Restructuring Loan Modification Based On Post Modification Outstanding Balance [Line Items]
Loans, Past Due	17,755	20,847
Commercial Real Estate [Member] | Owner-Occupied [Member] | Current & Other [Member]
Disclosure Details Of Troubled Debt Restructuring Loan Modification Based On Post Modification Outstanding Balance [Line Items]
Loans, Past Due	1,696,217	1,712,329
Commercial Real Estate [Member] | Nonowner-Occupied [Member]
Disclosure Details Of Troubled Debt Restructuring Loan Modification Based On Post Modification Outstanding Balance [Line Items]
Total Financing Receivables	5,955,839	5,957,288
Loans, Recorded Investment >90 Days & Accruing	1,506	545
Commercial Real Estate [Member] | Nonowner-Occupied [Member] | 30-89 Days Past Due [Member]
Disclosure Details Of Troubled Debt Restructuring Loan Modification Based On Post Modification Outstanding Balance [Line Items]
Loans, Past Due	15,290	5,791
Commercial Real Estate [Member] | Nonowner-Occupied [Member] | 90 Days or more Past Due [Member]
Disclosure Details Of Troubled Debt Restructuring Loan Modification Based On Post Modification Outstanding Balance [Line Items]
Loans, Past Due	10,892	18,829
Commercial Real Estate [Member] | Nonowner-Occupied [Member] | Total Past Due [Member]
Disclosure Details Of Troubled Debt Restructuring Loan Modification Based On Post Modification Outstanding Balance [Line Items]
Loans, Past Due	26,182	24,620
Commercial Real Estate [Member] | Nonowner-Occupied [Member] | Current & Other [Member]
Disclosure Details Of Troubled Debt Restructuring Loan Modification Based On Post Modification Outstanding Balance [Line Items]
Loans, Past Due	5,929,657	5,932,668
Other Commercial [Member]
Disclosure Details Of Troubled Debt Restructuring Loan Modification Based On Post Modification Outstanding Balance [Line Items]
Total Financing Receivables	3,481,156	3,462,361
Loans, Recorded Investment >90 Days & Accruing	1,919	6,569
Other Commercial [Member] | 30-89 Days Past Due [Member]
Disclosure Details Of Troubled Debt Restructuring Loan Modification Based On Post Modification Outstanding Balance [Line Items]
Loans, Past Due	42,699	21,444
Other Commercial [Member] | 90 Days or more Past Due [Member]
Disclosure Details Of Troubled Debt Restructuring Loan Modification Based On Post Modification Outstanding Balance [Line Items]
Loans, Past Due	9,196	15,883
Other Commercial [Member] | Total Past Due [Member]
Disclosure Details Of Troubled Debt Restructuring Loan Modification Based On Post Modification Outstanding Balance [Line Items]
Loans, Past Due	51,895	37,327
Other Commercial [Member] | Current & Other [Member]
Disclosure Details Of Troubled Debt Restructuring Loan Modification Based On Post Modification Outstanding Balance [Line Items]
Loans, Past Due	3,429,261	3,425,034
Residential Real Estate [Member]
Disclosure Details Of Troubled Debt Restructuring Loan Modification Based On Post Modification Outstanding Balance [Line Items]
Total Financing Receivables	4,104,848	3,691,560
Loans, Recorded Investment >90 Days & Accruing	9,994	8,241
Residential Real Estate [Member] | 30-89 Days Past Due [Member]
Disclosure Details Of Troubled Debt Restructuring Loan Modification Based On Post Modification Outstanding Balance [Line Items]
Loans, Past Due	20,506	19,488
Residential Real Estate [Member] | 90 Days or more Past Due [Member]
Disclosure Details Of Troubled Debt Restructuring Loan Modification Based On Post Modification Outstanding Balance [Line Items]
Loans, Past Due	23,448	23,495
Residential Real Estate [Member] | Total Past Due [Member]
Disclosure Details Of Troubled Debt Restructuring Loan Modification Based On Post Modification Outstanding Balance [Line Items]
Loans, Past Due	43,954	42,983
Residential Real Estate [Member] | Current & Other [Member]
Disclosure Details Of Troubled Debt Restructuring Loan Modification Based On Post Modification Outstanding Balance [Line Items]
Loans, Past Due	4,060,894	3,648,577
Consumer [Member] | Bankcard [Member]
Disclosure Details Of Troubled Debt Restructuring Loan Modification Based On Post Modification Outstanding Balance [Line Items]
Total Financing Receivables	8,651	8,913
Loans, Recorded Investment >90 Days & Accruing	43	187
Consumer [Member] | Bankcard [Member] | 30-89 Days Past Due [Member]
Disclosure Details Of Troubled Debt Restructuring Loan Modification Based On Post Modification Outstanding Balance [Line Items]
Loans, Past Due	44	100
Consumer [Member] | Bankcard [Member] | 90 Days or more Past Due [Member]
Disclosure Details Of Troubled Debt Restructuring Loan Modification Based On Post Modification Outstanding Balance [Line Items]
Loans, Past Due	43	187
Consumer [Member] | Bankcard [Member] | Total Past Due [Member]
Disclosure Details Of Troubled Debt Restructuring Loan Modification Based On Post Modification Outstanding Balance [Line Items]
Loans, Past Due	87	287
Consumer [Member] | Bankcard [Member] | Current & Other [Member]
Disclosure Details Of Troubled Debt Restructuring Loan Modification Based On Post Modification Outstanding Balance [Line Items]
Loans, Past Due	8,564	8,626
Consumer [Member] | Other Consumer [Member]
Disclosure Details Of Troubled Debt Restructuring Loan Modification Based On Post Modification Outstanding Balance [Line Items]
Total Financing Receivables	1,334,375	1,183,844
Loans, Recorded Investment >90 Days & Accruing	3,270	2,445
Consumer [Member] | Other Consumer [Member] | 30-89 Days Past Due [Member]
Disclosure Details Of Troubled Debt Restructuring Loan Modification Based On Post Modification Outstanding Balance [Line Items]
Loans, Past Due	22,661	17,264
Consumer [Member] | Other Consumer [Member] | 90 Days or more Past Due [Member]
Disclosure Details Of Troubled Debt Restructuring Loan Modification Based On Post Modification Outstanding Balance [Line Items]
Loans, Past Due	3,791	2,615
Consumer [Member] | Other Consumer [Member] | Total Past Due [Member]
Disclosure Details Of Troubled Debt Restructuring Loan Modification Based On Post Modification Outstanding Balance [Line Items]
Loans, Past Due	26,452	19,879
Consumer [Member] | Other Consumer [Member] | Current & Other [Member]
Disclosure Details Of Troubled Debt Restructuring Loan Modification Based On Post Modification Outstanding Balance [Line Items]
Loans, Past Due	$ 1,307,923	$ 1,163,965