Fair Value Disclosures - Financial Assets and Financial Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($)	Dec. 31, 2022	Dec. 31, 2021
Activity in available-for-sale securities and other investments:
Securities available-for-sale, at fair value	$ 5,474,359,000	$ 6,573,179,000
Loans held-for-sale	(11,965,000)	(37,810,000)
Obligations of State and Political Subdivisions [Member]
Activity in available-for-sale securities and other investments:
Securities available-for-sale, at fair value	1,898,611,000	2,753,471,000
Residential Mortgage-Backed Securities [Member]
Activity in available-for-sale securities and other investments:
Securities available-for-sale, at fair value	2,616,566,000	3,259,449,000
Commercial Mortgage-Backed Securities [Member]
Activity in available-for-sale securities and other investments:
Securities available-for-sale, at fair value	374,869,000	365,120,000
IRLCs [Member]
Activity in available-for-sale securities and other investments:
Asset Derivative Fair Value	400,000	1,279,000
Liability Derivative Fair Value	0	0
Forward Mortgage-Backed Securities Trades [Member]
Activity in available-for-sale securities and other investments:
Asset Derivative Fair Value	85,000	0
Liability Derivative Fair Value	0	147,000
U.S. Treasury securities [Member]
Activity in available-for-sale securities and other investments:
Securities available-for-sale, at fair value	482,549,000	126,841,000
Fair Value, Measurements, Recurring [Member]
Activity in available-for-sale securities and other investments:
Securities available-for-sale, at fair value	5,474,359,000	6,573,179,000
Loans held-for-sale	(10,497,000)	(34,122,000)
Fair Value, Measurements, Recurring [Member] \| Obligations of State and Political Subdivisions [Member]
Activity in available-for-sale securities and other investments:
Securities available-for-sale, at fair value	1,898,611,000	2,753,471,000
Fair Value, Measurements, Recurring [Member] \| Residential Mortgage-Backed Securities [Member]
Activity in available-for-sale securities and other investments:
Securities available-for-sale, at fair value	2,616,566,000	3,259,449,000
Fair Value, Measurements, Recurring [Member] \| Commercial Mortgage-Backed Securities [Member]
Activity in available-for-sale securities and other investments:
Securities available-for-sale, at fair value	374,869,000	365,120,000
Fair Value, Measurements, Recurring [Member] \| IRLCs [Member]
Activity in available-for-sale securities and other investments:
Asset Derivative Fair Value	400,000	1,279,000
Fair Value, Measurements, Recurring [Member] \| Forward Mortgage-Backed Securities Trades [Member]
Activity in available-for-sale securities and other investments:
Loans held-for-sale	(85,000)
Liability Derivative Fair Value		(147,000)
Fair Value, Measurements, Recurring [Member] \| U.S. Treasury securities [Member]
Activity in available-for-sale securities and other investments:
Securities available-for-sale, at fair value	482,549,000	126,841,000
Fair Value, Measurements, Recurring [Member] \| Corporate Bonds [Member]
Activity in available-for-sale securities and other investments:
Securities available-for-sale, at fair value	97,850,000	63,868,000
Fair Value, Measurements, Recurring [Member] \| Level 1 Inputs [Member]
Activity in available-for-sale securities and other investments:
Securities available-for-sale, at fair value	486,463,000	131,271,000
Fair Value, Measurements, Recurring [Member] \| Level 1 Inputs [Member] \| U.S. Treasury securities [Member]
Activity in available-for-sale securities and other investments:
Securities available-for-sale, at fair value	482,549,000	126,841,000
Fair Value, Measurements, Recurring [Member] \| Level 2 Inputs [Member]
Activity in available-for-sale securities and other investments:
Securities available-for-sale, at fair value	4,987,896,000	6,441,908,000
Loans held-for-sale	(10,497,000)	(34,122,000)
Fair Value, Measurements, Recurring [Member] \| Level 2 Inputs [Member] \| Obligations of State and Political Subdivisions [Member]
Activity in available-for-sale securities and other investments:
Securities available-for-sale, at fair value	1,898,611,000	2,753,471,000
Fair Value, Measurements, Recurring [Member] \| Level 2 Inputs [Member] \| Residential Mortgage-Backed Securities [Member]
Activity in available-for-sale securities and other investments:
Securities available-for-sale, at fair value	2,616,566,000	3,259,449,000
Fair Value, Measurements, Recurring [Member] \| Level 2 Inputs [Member] \| Commercial Mortgage-Backed Securities [Member]
Activity in available-for-sale securities and other investments:
Securities available-for-sale, at fair value	374,869,000	365,120,000
Fair Value, Measurements, Recurring [Member] \| Level 2 Inputs [Member] \| IRLCs [Member]
Activity in available-for-sale securities and other investments:
Asset Derivative Fair Value	400,000	1,279,000
Fair Value, Measurements, Recurring [Member] \| Level 2 Inputs [Member] \| Forward Mortgage-Backed Securities Trades [Member]
Activity in available-for-sale securities and other investments:
Loans held-for-sale	(85,000)
Liability Derivative Fair Value		(147,000)
Fair Value, Measurements, Recurring [Member] \| Level 2 Inputs [Member] \| Corporate Bonds [Member]
Activity in available-for-sale securities and other investments:
Securities available-for-sale, at fair value	97,850,000	63,868,000
Other Securities [Member] \| Fair Value, Measurements, Recurring [Member]
Activity in available-for-sale securities and other investments:
Securities available-for-sale, at fair value	3,914,000	4,430,000
Other Securities [Member] \| Fair Value, Measurements, Recurring [Member] \| Level 1 Inputs [Member]
Activity in available-for-sale securities and other investments:
Securities available-for-sale, at fair value	$ 3,914,000	$ 4,430,000

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Fair value, before effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets elected not to be offset. Excludes assets not subject to a master netting arrangement.

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Amount, after valuation allowance, of financing receivable held for sale and not part of disposal group. Excludes loan covered under loss sharing agreement and loan classified as investment in debt security.

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