Fair Value Measurements (Impaired Loans Remeasured and Reported at Fair Value of Underlying Collateral) (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying value of impaired loans before allocations		$ 99,453
Specific valuation allowance allocations		(28,483)
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying value of impaired loans before allocations	$ 1,559	2,354	$ 12,517
Specific valuation allowance allocations	(450)	(383)	(2,599)
Fair value	1,109	1,971	9,918
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying value of impaired loans before allocations	34,302	65,176	22,688
Specific valuation allowance allocations	(11,151)	(18,019)
Reversal of specific valuation allowance allocations			9,260
Fair value	$ 23,151	$ 47,157	$ 31,948