Derivative Financial Instruments - Information about Fair Values of Derivative Instruments in Consolidated Statement of Income (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Derivative Instruments, Gain (Loss) [Line Items]
Derivatives not designated as hedging instruments, derivatives	$ 10,000	$ 10,000	$ 24,000	$ 36,000
Interest rate swap agreements | Designated as Hedging Instrument | Fair value hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Derivatives in fair value hedging relationships, derivative	130,000	(61,000)	52,000	(95,000)
Derivatives in fair value hedging relationships, hedged item	$ (130,000)	$ 61,000	$ (52,000)	$ 96,000
Interest rate swap agreements | Fixed Rate Long-Term Borrowings | Designated as Hedging Instrument | Fair value hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Other costs of operations	Other costs of operations	Other costs of operations	Other costs of operations
Derivatives in fair value hedging relationships, derivative	$ 130,000	$ (61,000)	$ 52,000	$ (95,000)
Derivatives in fair value hedging relationships, hedged item	(130,000)	61,000	(52,000)	96,000
Interest rate swap agreements | Fixed Rate Available For Sale Securities | Designated as Hedging Instrument | Fair value hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Derivatives in fair value hedging relationships, derivative	0		0
Derivatives in fair value hedging relationships, hedged item	0		0
Interest Rate Contracts
Derivative Instruments, Gain (Loss) [Line Items]
Derivatives not designated as hedging instruments, derivatives	5,000	6,000	11,000	25,000
Foreign exchange and other option and futures contracts
Derivative Instruments, Gain (Loss) [Line Items]
Derivatives not designated as hedging instruments, derivatives	$ 5,000	$ 4,000	$ 13,000	$ 11,000