Fair Value Measurements - Estimated Fair Values of Financial Instruments (Detail) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023	Dec. 31, 2022
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	$ 8,464,517	$ 8,687,276	$ 9,301,774	$ 12,028,132
Securities held to maturity, net of allowance for credit losses of $310 at both March 31, 2024 and December 31, 2023	3,600,729	3,619,428
Loans, net	19,137,909	18,578,255
Deposits	40,806,486	41,920,568
Federal funds purchased	41,200	14,200
Repurchase agreements	3,943,207	4,127,188
Junior subordinated deferrable interest debentures	123,141	123,127
Subordinated notes	99,530	99,491
Carrying Amount [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	8,464,517	8,687,276
Securities held to maturity, net of allowance for credit losses of $310 at both March 31, 2024 and December 31, 2023	3,600,729	3,619,428
Accrued interest receivable	206,090	251,385
Deposits	40,806,486	41,920,568
Federal funds purchased	41,200	14,200
Repurchase agreements	3,943,207	4,127,188
Junior subordinated deferrable interest debentures	123,141	123,127
Subordinated notes	99,530	99,491
Accrued interest payable	65,102	61,222
Carrying Amount [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans, net	19,137,909	18,578,255
Estimated Fair Value [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	8,464,517	8,687,276
Securities held to maturity, net of allowance for credit losses of $310 at both March 31, 2024 and December 31, 2023	3,451,316	3,532,044
Accrued interest receivable	206,090	251,385
Deposits	40,792,337	41,903,580
Federal funds purchased	41,200	14,200
Repurchase agreements	3,943,207	4,127,188
Junior subordinated deferrable interest debentures	123,712	123,712
Subordinated notes	96,513	96,071
Accrued interest payable	65,102	61,222
Estimated Fair Value [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans, net	$ 18,637,078	$ 18,117,369