Income Taxes (Narrative) (Detail) - USD ($) $ / shares in Units, $ in Thousands		12 Months Ended
	Dec. 21, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Tax Credit Carryforward [Line Items]
Operating loss carryforwards		$ 18,000
Income tax expense (benefit), intraperiod tax allocation		$ 14,522	$ 14,802	$ 12,657
Reduction in net deferred tax liability				$ 400
Effective tax rate, Statutory federal tax	35.00%	21.00%	21.00%	35.00%
Income tax expense		$ 14,447	$ 14,759	$ 12,605
Estimated Tax Act impact on earnings per common share				$ 0.04
Effective tax rate, Share-based compensation		(7.00%)	(2.60%)	(3.00%)
Maryland State [Member]
Tax Credit Carryforward [Line Items]
Operating loss carryforwards expiration year		2030