(Reserve for Unfunded Commitments) (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Accounting Standards Update 2016-13 [Member]
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning balance	$ 0	$ 0	$ 9,139	$ 0
SEC Schedule, 12-09, Allowance, Credit Loss [Member]
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning balance	10,739	2,537	2,367	2,506
Provision (benefit) charged to non-interest expense	1,146	(68)	379	(37)
Ending balance	$ 11,885	$ 2,469	$ 11,885	$ 2,469