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, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Derivative Instruments, Gain (Loss) [Line Items]
Derivatives not designated as hedging instruments, Derivatives	$ (396)	$ (3,290)	$ (3,148)	$ 15,543
Interest Rate Swap Agreements [Member] | Fixed Rate Long-Term Borrowings [Member] | Derivatives Designated and Qualifying as Hedging Instruments [Member] | Fair Value Hedges [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivatives in fair value hedging relationships, Derivatives	(9,713)	(13,067)	(42,217)	75,760
Derivatives in fair value hedging relationships, Hedged item	9,636	12,822	41,456	(75,607)
Interest Rate Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivatives not designated as hedging instruments, Derivatives	(3,456)	(4,776)	(9,434)	8,988
Foreign Exchange and Other Option and Futures Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivatives not designated as hedging instruments, Derivatives	$ 3,060	$ 1,486	$ 6,286	$ 6,555