Derivative Financial Instruments (Counterparty Credit Risk Narrative) (Detail) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Dec. 31, 2020
Derivative [Line Items]
Maximum Length of Time Hedged in Cash Flow Hedge	3 years 1 month 6 days
Derivative instrument asset, Amount Offset	$ 30,234	$ 33,043
Credit Derivative, Maximum Exposure, Undiscounted	191,000
Cash and Due from Banks [Member]
Derivative [Line Items]
Derivative, Collateral, Right to Reclaim Cash	32,200
Valuation, Market Approach [Member]
Derivative [Line Items]
Credit Derivative, Maximum Exposure, Undiscounted	36,000
CME [Member]
Derivative [Line Items]
Derivative instrument asset, Amount Offset	$ 72,700