Fair Value Measurements - Estimated Fair Value of Financial Instruments (Detail) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and short-term investments	$ 4,121,276	$ 2,638,384
Securities available for sale	6,668,615	7,006,347
Securities held to maturity (exclusive of allowance for credit losses)	5,810,591	5,861,599
Trading securities	28,887	17,980
Other securities	428,149	349,758
Loans (exclusive of allowance for credit losses)	22,487,361	21,033,167
Derivatives	112,241	48,121
Demand and savings deposits	30,326,969	31,721,995
Time deposits	3,193,492	917,138
Other borrowings	3,850,583	2,222,167
Long-term debt	382,280	381,311
Derivatives	118,562	126,334
Estimate of Fair Value Measurement [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and short-term investments	4,121,276	2,638,384
Securities available for sale	6,668,615	7,006,347
Securities held to maturity (exclusive of allowance for credit losses)	5,234,236	5,280,659
Trading securities	28,887	17,980
Other securities	428,149	349,758
Loans (exclusive of allowance for credit losses)	22,295,499	20,816,899
Derivatives	112,241	48,121
Demand and savings deposits	30,326,969	31,721,995
Time deposits	3,200,832	917,138
Other borrowings	3,850,583	2,222,167
Long-term debt	415,254	418,737
Derivatives	118,562	126,334
Commitments to extend credit for loans	5,429	9,260
Commercial letters of credit	54	185
Standby letters of credit	2,185	3,982
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	3,811,438	1,686,787
Securities available for sale	1,130,480	1,144,570
Trading securities	819	2,384
Other securities	10,925	10,782
Demand and savings deposits	30,326,969	31,721,995
Other borrowings	73,981	62,480
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	309,838	951,597
Securities available for sale	5,538,135	5,861,777
Securities held to maturity (exclusive of allowance for credit losses)	5,234,236	5,280,659
Trading securities	28,068	15,596
Other securities	417,224	338,976
Loans (exclusive of allowance for credit losses)	22,295,499	20,816,899
Derivatives	112,241	48,121
Time deposits	3,200,832	917,138
Other borrowings	3,776,602	2,159,687
Long-term debt	415,254	418,737
Derivatives	$ 118,562	$ 126,334