Fair Value Measurements - Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Mar. 31, 2025	Dec. 31, 2024
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities	$ 35,461	$ 28,533
Available-for-sale securities	10,895,659	7,774,334
Derivative Assets, Fair Value	294,003	234,443
Derivative Liabilities, Fair Value	145,962	107,442
Securities sold not yet purchased	11,900	7,100
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities	15,253	8,695
Available-for-sale securities	1,883,640	1,643,243
Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities	20,208	19,838
Available-for-sale securities	9,012,019	6,131,091
U.S. Treasury [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	1,585,179	1,326,073
U.S. Agencies [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	107,664	129,047
Mortgage-backed [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	5,960,927	4,420,930
State and political subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	2,430,300	1,218,569
Corporates [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	298,461	317,170
Fair Value Measurement, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities	35,461	28,533
Available-for-sale securities	10,895,659	7,774,334
Equity securities with readily determinable fair values	12,032	11,596
Derivative Assets, Fair Value	294,003	234,443
Total	11,237,155	8,048,906
Derivative Liabilities, Fair Value	145,962	107,442
Securities sold not yet purchased	11,925	7,100
Total	157,887	114,542
Fair Value Measurement, Recurring [Member] | Collateralized loan obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	513,128	362,545
Fair Value Measurement, Recurring [Member] | Trading - other [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities	2,130	140
Fair Value Measurement, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities	15,253	8,695
Available-for-sale securities	1,883,640	1,643,243
Equity securities with readily determinable fair values	12,032	11,596
Total	1,910,925	1,663,534
Fair Value Measurement, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Trading - other [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities	2,130	140
Fair Value Measurement, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities	20,208	19,838
Available-for-sale securities	9,012,019	6,131,091
Derivative Assets, Fair Value	294,003	234,443
Total	9,326,230	6,385,372
Derivative Liabilities, Fair Value	145,962	107,442
Securities sold not yet purchased	11,925	7,100
Total	157,887	114,542
Fair Value Measurement, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Collateralized loan obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	513,128	362,545
Fair Value Measurement, Recurring [Member] | U.S. Treasury [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities	629	1,620
Available-for-sale securities	1,585,179	1,326,073
Fair Value Measurement, Recurring [Member] | U.S. Treasury [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities	629	1,620
Available-for-sale securities	1,585,179	1,326,073
Fair Value Measurement, Recurring [Member] | U.S. Agencies [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities	6,980	8,369
Available-for-sale securities	107,664	129,047
Fair Value Measurement, Recurring [Member] | U.S. Agencies [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities	6,980	8,369
Available-for-sale securities	107,664	129,047
Fair Value Measurement, Recurring [Member] | Mortgage-backed [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	5,960,927	4,420,930
Fair Value Measurement, Recurring [Member] | Mortgage-backed [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	5,960,927	4,420,930
Fair Value Measurement, Recurring [Member] | State and political subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities	13,228	11,469
Available-for-sale securities	2,430,300	1,218,569
Fair Value Measurement, Recurring [Member] | State and political subdivisions [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities	13,228	11,469
Available-for-sale securities	2,430,300	1,218,569
Fair Value Measurement, Recurring [Member] | Corporates [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities	12,494	6,935
Available-for-sale securities	298,461	317,170
Fair Value Measurement, Recurring [Member] | Corporates [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities	12,494	6,935
Available-for-sale securities	$ 298,461	$ 317,170