Credit Quality - Schedule of Age Analysis of its Past Due Loans, Segregated by Class of Loans and Leases (Detail) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Financing Receivable, Past Due [Line Items]
Total Financing Receivables	$ 21,532,568	$ 21,373,185
Loans, Recorded Investment >90 Days & Accruing	11,329	14,579
30-89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Loans, Past Due	69,393	83,950
90 Days or more Past Due [Member]
Financing Receivable, Past Due [Line Items]
Loans, Past Due	74,382	45,498
Total Past Due [Member]
Financing Receivable, Past Due [Line Items]
Loans, Past Due	143,775	129,448
Current & Other [Member]
Financing Receivable, Past Due [Line Items]
Loans, Past Due	21,388,793	21,243,737
Construction & Land Development [Member]
Financing Receivable, Past Due [Line Items]
Total Financing Receivables	2,997,678	3,148,245
Loans, Recorded Investment >90 Days & Accruing	0	0
Construction & Land Development [Member] | 30-89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Loans, Past Due	957	879
Construction & Land Development [Member] | 90 Days or more Past Due [Member]
Financing Receivable, Past Due [Line Items]
Loans, Past Due	6,027	6,423
Construction & Land Development [Member] | Total Past Due [Member]
Financing Receivable, Past Due [Line Items]
Loans, Past Due	6,984	7,302
Construction & Land Development [Member] | Current & Other [Member]
Financing Receivable, Past Due [Line Items]
Loans, Past Due	2,990,694	3,140,943
Commercial Real Estate [Member] | Owner-Occupied [Member]
Financing Receivable, Past Due [Line Items]
Total Financing Receivables	1,624,746	1,598,231
Loans, Recorded Investment >90 Days & Accruing	95	110
Commercial Real Estate [Member] | Owner-Occupied [Member] | 30-89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Loans, Past Due	3,503	6,361
Commercial Real Estate [Member] | Owner-Occupied [Member] | 90 Days or more Past Due [Member]
Financing Receivable, Past Due [Line Items]
Loans, Past Due	8,840	6,335
Commercial Real Estate [Member] | Owner-Occupied [Member] | Total Past Due [Member]
Financing Receivable, Past Due [Line Items]
Loans, Past Due	12,343	12,696
Commercial Real Estate [Member] | Owner-Occupied [Member] | Current & Other [Member]
Financing Receivable, Past Due [Line Items]
Loans, Past Due	1,612,403	1,585,535
Commercial Real Estate [Member] | Nonowner-Occupied [Member]
Financing Receivable, Past Due [Line Items]
Total Financing Receivables	7,010,266	6,718,343
Loans, Recorded Investment >90 Days & Accruing	0	2,460
Commercial Real Estate [Member] | Nonowner-Occupied [Member] | 30-89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Loans, Past Due	10,041	10,373
Commercial Real Estate [Member] | Nonowner-Occupied [Member] | 90 Days or more Past Due [Member]
Financing Receivable, Past Due [Line Items]
Loans, Past Due	6,950	13,146
Commercial Real Estate [Member] | Nonowner-Occupied [Member] | Total Past Due [Member]
Financing Receivable, Past Due [Line Items]
Loans, Past Due	16,991	23,519
Commercial Real Estate [Member] | Nonowner-Occupied [Member] | Current & Other [Member]
Financing Receivable, Past Due [Line Items]
Loans, Past Due	6,993,275	6,694,824
Other Commercial [Member]
Financing Receivable, Past Due [Line Items]
Total Financing Receivables	3,539,826	3,572,440
Loans, Recorded Investment >90 Days & Accruing	582	560
Other Commercial [Member] | 30-89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Loans, Past Due	4,108	3,218
Other Commercial [Member] | 90 Days or more Past Due [Member]
Financing Receivable, Past Due [Line Items]
Loans, Past Due	33,979	1,224
Other Commercial [Member] | Total Past Due [Member]
Financing Receivable, Past Due [Line Items]
Loans, Past Due	38,087	4,442
Other Commercial [Member] | Current & Other [Member]
Financing Receivable, Past Due [Line Items]
Loans, Past Due	3,501,739	3,567,998
Residential Real Estate [Member]
Financing Receivable, Past Due [Line Items]
Total Financing Receivables	5,366,385	5,271,236
Loans, Recorded Investment >90 Days & Accruing	6,981	6,244
Residential Real Estate [Member] | 30-89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Loans, Past Due	27,179	26,523
Residential Real Estate [Member] | 90 Days or more Past Due [Member]
Financing Receivable, Past Due [Line Items]
Loans, Past Due	12,881	12,136
Residential Real Estate [Member] | Total Past Due [Member]
Financing Receivable, Past Due [Line Items]
Loans, Past Due	40,060	38,659
Residential Real Estate [Member] | Current & Other [Member]
Financing Receivable, Past Due [Line Items]
Loans, Past Due	5,326,325	5,232,577
Consumer [Member] | Bankcard [Member]
Financing Receivable, Past Due [Line Items]
Total Financing Receivables	9,431	9,962
Loans, Recorded Investment >90 Days & Accruing	138	127
Consumer [Member] | Bankcard [Member] | 30-89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Loans, Past Due	122	145
Consumer [Member] | Bankcard [Member] | 90 Days or more Past Due [Member]
Financing Receivable, Past Due [Line Items]
Loans, Past Due	138	127
Consumer [Member] | Bankcard [Member] | Total Past Due [Member]
Financing Receivable, Past Due [Line Items]
Loans, Past Due	260	272
Consumer [Member] | Bankcard [Member] | Current & Other [Member]
Financing Receivable, Past Due [Line Items]
Loans, Past Due	9,171	9,690
Consumer [Member] | Other Consumer [Member]
Financing Receivable, Past Due [Line Items]
Total Financing Receivables	984,236	1,054,728
Loans, Recorded Investment >90 Days & Accruing	3,533	5,078
Consumer [Member] | Other Consumer [Member] | 30-89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Loans, Past Due	23,483	36,451
Consumer [Member] | Other Consumer [Member] | 90 Days or more Past Due [Member]
Financing Receivable, Past Due [Line Items]
Loans, Past Due	5,567	6,107
Consumer [Member] | Other Consumer [Member] | Total Past Due [Member]
Financing Receivable, Past Due [Line Items]
Loans, Past Due	29,050	42,558
Consumer [Member] | Other Consumer [Member] | Current & Other [Member]
Financing Receivable, Past Due [Line Items]
Loans, Past Due	$ 955,186	$ 1,012,170