Borrowed Funds - Carrying Amounts and Market Values of Securities and Related Repurchase Liabilities and Weighted Average Interest Rates of Repurchase Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Assets Sold under Agreements to Repurchase [Line Items]
Securities Fair Market Value	$ 3,211,609	$ 2,130,670
Repurchase Liabilities	$ 3,225,838	$ 2,249,861
Weighted Average Interest Rate	0.25%	0.52%
2 to 29 days [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Securities Fair Market Value	$ 2,797,268	$ 1,625,230
Repurchase Liabilities	$ 2,820,788	$ 1,759,559
Weighted Average Interest Rate	0.19%	0.34%
30 to 90 Days [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Securities Fair Market Value	$ 414,091	$ 504,435
Repurchase Liabilities	$ 404,800	$ 489,302
Weighted Average Interest Rate	0.70%	1.17%
Over 90 Days [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Securities Fair Market Value	$ 250	$ 1,005
Repurchase Liabilities	$ 250	$ 1,000
Weighted Average Interest Rate	0.01%