Fair Value Measurements - Estimated Fair Value of Financial Instruments (Detail) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and short-term investments	$ 3,240,996	$ 10,472,084
Securities available for sale	7,739,216	11,976,514
Total held to maturity securities	5,709,541	1,480,416
Trading securities	9,646	31,875
Other securities	342,543	327,098
Loans (exclusive of allowance for credit losses)	18,972,908	17,172,148
Derivatives	23,626	57,680
Demand and savings deposits	30,932,642	34,748,286
Time deposits	553,382	851,641
Other borrowings	2,661,283	3,238,435
Long-term debt	272,505	271,544
Derivatives	71,268	13,944
Estimate of Fair Value Measurement [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and short-term investments	3,240,996	10,472,084
Securities available for sale	7,739,216	11,976,514
Total held to maturity securities	5,245,451	1,442,391
Trading securities	9,646	31,875
Other securities	342,543	327,098
Loans (exclusive of allowance for credit losses)	18,971,934	17,506,662
Derivatives	23,626	57,680
Demand and savings deposits	30,932,642	34,748,286
Time deposits	553,382	851,641
Other borrowings	2,661,283	3,238,435
Long-term debt	273,596	285,961
Derivatives	71,268	13,944
Commitments to extend credit for loans	4,116	7,841
Commercial letters of credit	113	179
Standby letters of credit	2,074	3,553
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and short-term investments	2,205,537	9,255,727
Securities available for sale	1,134,537	387,020
Trading securities	3,749	5,985
Other securities	40,639	64,149
Demand and savings deposits	30,932,642	34,748,286
Other borrowings	52,987	12,597
Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and short-term investments	1,035,459	1,216,357
Securities available for sale	6,604,679	11,589,494
Total held to maturity securities	5,245,451	1,442,391
Trading securities	5,897	25,890
Other securities	301,904	262,949
Loans (exclusive of allowance for credit losses)	18,971,934	17,506,662
Derivatives	23,626	57,680
Time deposits	553,382	851,641
Other borrowings	2,608,296	3,225,838
Long-term debt	273,596	285,961
Derivatives	$ 71,268	$ 13,944