Fair Value Measurements - Estimated Fair Values of Financial Instruments (Detail) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022	Sep. 30, 2022	Dec. 31, 2021
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	$ 7,618,083	$ 12,028,132	$ 13,632,698	$ 16,583,000
Securities held to maturity, net of allowance for credit losses of $310 at September 30, 2023 and $158 at December 31, 2022	3,628,123	2,639,083
Loans, net	18,157,024	16,927,348
Deposits	40,992,235	43,954,196
Federal funds purchased	25,950	51,650
Repurchase agreements	3,722,245	4,660,641
Junior subordinated deferrable interest debentures	123,112	123,069
Subordinated notes	99,452	99,335
Carrying Amount [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	7,618,083	12,028,132
Securities held to maturity, net of allowance for credit losses of $310 at September 30, 2023 and $158 at December 31, 2022	3,628,123	2,639,083
Accrued interest receivable	199,344	243,682
Deposits	40,992,235	43,954,196
Federal funds purchased	25,950	51,650
Repurchase agreements	3,722,245	4,660,641
Junior subordinated deferrable interest debentures	123,112	123,069
Subordinated notes	99,452	99,335
Accrued interest payable	51,468	18,444
Carrying Amount [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans, net	18,157,024	16,927,348
Estimated Fair Value [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	7,618,083	12,028,132
Securities held to maturity, net of allowance for credit losses of $310 at September 30, 2023 and $158 at December 31, 2022	3,231,691	2,467,865
Accrued interest receivable	199,344	243,682
Deposits	40,971,688	43,920,741
Federal funds purchased	25,950	51,650
Repurchase agreements	3,722,245	4,660,641
Junior subordinated deferrable interest debentures	123,712	123,712
Subordinated notes	94,311	97,014
Accrued interest payable	51,468	18,444
Estimated Fair Value [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans, net	$ 17,496,332	$ 16,343,417