Fair Value Measurements - Financial Assets and Financial Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at estimated fair value	$ 17,399,107	$ 13,924,628
Trading account securities	25,008	25,162
Derivative assets	127,209	23,339
Derivative liabilities	97,033	114,019
Interest rate swaps, caps and floors [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	78,898	44,310
Derivative liabilities	99,093	25,261
Commodity swaps and options [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	145,933	114,757
Derivative liabilities	144,385	113,261
Foreign Exchange Forward [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	252	33
Derivative liabilities	252	55
U.S. Treasury [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at estimated fair value	5,022,617	2,179,433
Trading account securities	25,008	24,237
Residential Mortgage Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at estimated fair value	5,698,809	4,066,265
States and political subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at estimated fair value	6,635,298	7,636,571
Trading account securities		925
Other [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at estimated fair value	42,383	42,359
Level 1 [Member] | Foreign Exchange Forward [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	252	33
Derivative liabilities	252	55
Level 1 [Member] | U.S. Treasury [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at estimated fair value	5,022,617	2,179,433
Trading account securities	25,008	24,237
Level 2 [Member] | Interest rate swaps, caps and floors [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	78,898	44,310
Derivative liabilities	99,093	25,261
Level 2 [Member] | Commodity swaps and options [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	145,933	114,757
Derivative liabilities	144,385	113,261
Level 2 [Member] | Residential Mortgage Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at estimated fair value	5,698,809	4,066,265
Level 2 [Member] | States and political subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at estimated fair value	6,635,298	7,636,571
Trading account securities		925
Level 2 [Member] | Other [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale, at estimated fair value	$ 42,383	$ 42,359