Credit Quality - Schedule of Age Analysis of its Past Due Loans, Segregated by Class of Loans and Leases (Detail) - USD ($) $ in Thousands	Sep. 30, 2026	Dec. 31, 2025
Financing Receivable, Past Due [Line Items]
Loans, Past Due	$ 25,473,482	$ 24,720,620
Loans, Recorded Investment >90 Days & Accruing	9,987	4,974
30-89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Loans, Past Due	97,622	55,065
90 Days or more Past Due [Member]
Financing Receivable, Past Due [Line Items]
Loans, Past Due	109,894	101,466
Total Past Due [Member]
Financing Receivable, Past Due [Line Items]
Loans, Past Due	207,516	156,531
Current & Other [Member]
Financing Receivable, Past Due [Line Items]
Loans, Past Due	25,265,966	24,564,089
Construction & Land Development [Member]
Financing Receivable, Past Due [Line Items]
Loans, Past Due	3,398,426	3,570,902
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	1,704	1,508
Construction & Land Development [Member] \| 90 Days or more Past Due [Member]
Financing Receivable, Past Due [Line Items]
Loans, Past Due	2,681	1,301
Construction & Land Development [Member] \| Total Past Due [Member]
Financing Receivable, Past Due [Line Items]
Loans, Past Due	4,385	2,809
Construction & Land Development [Member] \| Current & Other [Member]
Financing Receivable, Past Due [Line Items]
Loans, Past Due	3,394,041	3,568,093
Commercial Real Estate [Member] \| Owner-Occupied [Member]
Financing Receivable, Past Due [Line Items]
Loans, Past Due	2,177,293	2,145,921
Loans, Recorded Investment >90 Days & Accruing	0	81
Commercial Real Estate [Member] \| Owner-Occupied [Member] \| 30-89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Loans, Past Due	6,935	4,754
Commercial Real Estate [Member] \| Owner-Occupied [Member] \| 90 Days or more Past Due [Member]
Financing Receivable, Past Due [Line Items]
Loans, Past Due	1,444	1,830
Commercial Real Estate [Member] \| Owner-Occupied [Member] \| Total Past Due [Member]
Financing Receivable, Past Due [Line Items]
Loans, Past Due	8,379	6,584
Commercial Real Estate [Member] \| Owner-Occupied [Member] \| Current & Other [Member]
Financing Receivable, Past Due [Line Items]
Loans, Past Due	2,168,914	2,139,337
Commercial Real Estate [Member] \| Nonowner-Occupied [Member]
Financing Receivable, Past Due [Line Items]
Loans, Past Due	9,033,200	8,343,520
Loans, Recorded Investment >90 Days & Accruing	3,499	0
Commercial Real Estate [Member] \| Nonowner-Occupied [Member] \| 30-89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Loans, Past Due	39,976	7,598
Commercial Real Estate [Member] \| Nonowner-Occupied [Member] \| 90 Days or more Past Due [Member]
Financing Receivable, Past Due [Line Items]
Loans, Past Due	78,140	71,038
Commercial Real Estate [Member] \| Nonowner-Occupied [Member] \| Total Past Due [Member]
Financing Receivable, Past Due [Line Items]
Loans, Past Due	118,116	78,636
Commercial Real Estate [Member] \| Nonowner-Occupied [Member] \| Current & Other [Member]
Financing Receivable, Past Due [Line Items]
Loans, Past Due	8,915,084	8,264,884
Other Commercial [Member]
Financing Receivable, Past Due [Line Items]
Loans, Past Due	3,774,652	3,784,833
Loans, Recorded Investment >90 Days & Accruing	649	591
Other Commercial [Member] \| 30-89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Loans, Past Due	8,150	2,490
Other Commercial [Member] \| 90 Days or more Past Due [Member]
Financing Receivable, Past Due [Line Items]
Loans, Past Due	7,354	6,569
Other Commercial [Member] \| Total Past Due [Member]
Financing Receivable, Past Due [Line Items]
Loans, Past Due	15,504	9,059
Other Commercial [Member] \| Current & Other [Member]
Financing Receivable, Past Due [Line Items]
Loans, Past Due	3,759,148	3,775,774
Residential Real Estate [Member]
Financing Receivable, Past Due [Line Items]
Loans, Past Due	6,257,512	6,098,262
Loans, Recorded Investment >90 Days & Accruing	5,602	3,701
Residential Real Estate [Member] \| 30-89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Loans, Past Due	32,110	25,026
Residential Real Estate [Member] \| 90 Days or more Past Due [Member]
Financing Receivable, Past Due [Line Items]
Loans, Past Due	19,442	19,124
Residential Real Estate [Member] \| Total Past Due [Member]
Financing Receivable, Past Due [Line Items]
Loans, Past Due	51,552	44,150
Residential Real Estate [Member] \| Current & Other [Member]
Financing Receivable, Past Due [Line Items]
Loans, Past Due	6,205,960	6,054,112
Consumer [Member] \| Bankcard [Member]
Financing Receivable, Past Due [Line Items]
Loans, Past Due	9,215	9,686
Loans, Recorded Investment >90 Days & Accruing	47	54
Consumer [Member] \| Bankcard [Member] \| 30-89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Loans, Past Due	82	28
Consumer [Member] \| Bankcard [Member] \| 90 Days or more Past Due [Member]
Financing Receivable, Past Due [Line Items]
Loans, Past Due	47	54
Consumer [Member] \| Bankcard [Member] \| Total Past Due [Member]
Financing Receivable, Past Due [Line Items]
Loans, Past Due	129	82
Consumer [Member] \| Bankcard [Member] \| Current & Other [Member]
Financing Receivable, Past Due [Line Items]
Loans, Past Due	9,086	9,604
Consumer [Member] \| Other Consumer [Member]
Financing Receivable, Past Due [Line Items]
Loans, Past Due	823,184	767,496
Loans, Recorded Investment >90 Days & Accruing	190	547
Consumer [Member] \| Other Consumer [Member] \| 30-89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Loans, Past Due	8,665	13,661
Consumer [Member] \| Other Consumer [Member] \| 90 Days or more Past Due [Member]
Financing Receivable, Past Due [Line Items]
Loans, Past Due	786	1,550
Consumer [Member] \| Other Consumer [Member] \| Total Past Due [Member]
Financing Receivable, Past Due [Line Items]
Loans, Past Due	9,451	15,211
Consumer [Member] \| Other Consumer [Member] \| Current & Other [Member]
Financing Receivable, Past Due [Line Items]
Loans, Past Due	$ 813,733	$ 752,285