Fair Value Measurements (Estimated Fair Values of Financial Instruments) (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash and cash equivalents	$ 8,687,276	$ 12,028,132	$ 16,583,000	$ 10,288,853
Securities held to maturity	3,619,428	2,639,083
Loans, net	18,578,255	16,927,348
Deposits	41,920,568	43,954,196
Federal funds purchased	14,200	51,650
Repurchase agreements	4,127,188	4,660,641
Junior subordinated deferrable interest debentures	123,127	123,069
Subordinated notes	99,491	99,335
Carrying Amount [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash and cash equivalents	8,687,276	12,028,132
Securities held to maturity	3,619,428	2,639,083
Accrued interest receivable	251,385	243,682
Deposits	41,920,568	43,954,196
Federal funds purchased	14,200	51,650
Repurchase agreements	4,127,188	4,660,641
Junior subordinated deferrable interest debentures	123,127	123,069
Subordinated notes	99,491	99,335
Accrued interest payable	61,222	18,444
Carrying Amount [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans, net	18,578,255	16,927,348
Estimated Fair Value [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash and cash equivalents	8,687,276	12,028,132
Securities held to maturity	3,532,044	2,467,865
Accrued interest receivable	251,385	243,682
Deposits	41,903,580	43,920,741
Federal funds purchased	14,200	51,650
Repurchase agreements	4,127,188	4,660,641
Junior subordinated deferrable interest debentures	123,712	123,712
Subordinated notes	96,071	97,014
Accrued interest payable	61,222	18,444
Estimated Fair Value [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans, net	$ 18,117,369	$ 16,343,417