Property And Equipment (Narrative) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Abstract]
Impairment of property and equipment	$ 0	$ 0	$ 0
Depreciation and amortization expense	$ 2,200	$ 3,800	$ 3,500