Derivative Financial Instruments - Information about Interest Rate Swap Agreements (Detail) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2023	Dec. 31, 2022
Derivative [Line Items]
Notional Amount	$ 25,977,000	$ 17,400,000
Average Maturity (in years)	2 years 4 months 24 days	1 year 7 months 6 days
Estimated Fair Value Gain (Loss)	$ 12,185	$ (7,892)
Interest Payments On Variable Rate Commercial Real Estate Loans [Member] | Cash Flow Hedges [Member]
Derivative [Line Items]
Notional Amount	$ 23,977,000	$ 15,900,000
Average Maturity (in years)	2 years	1 year 4 months 24 days
Weighted-Average Rate, Fixed	3.45%	1.91%
Weighted-Average Rate, Variable	5.32%	4.38%
Estimated Fair Value Gain (Loss)	$ 9,077	$ (7,059)
Fixed Rate Long-Term Borrowings [Member] | Fair Value Hedges [Member]
Derivative [Line Items]
Notional Amount	$ 2,000,000	$ 1,500,000
Average Maturity (in years)	6 years 7 months 6 days	3 years 3 months 18 days
Weighted-Average Rate, Fixed	3.11%	2.98%
Weighted-Average Rate, Variable	5.74%	4.52%
Estimated Fair Value Gain (Loss)	$ 3,108	$ (833)