Valuation and Qualifying Accounts (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Allowance for Doubtful Accounts
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	$ 868	$ 495	$ 359
Additions Charged to Costs and Expenses	776	334	233
Deductions/(Recoveries)	509	(39)	97
Balance at End of Period	1,135	868	495
Valuation Allowance of Deferred Tax Assets
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	9,013	6,607	7,477
Additions Charged to Costs and Expenses	70	2,406	(870)
Deductions/(Recoveries)	0	0	0
Balance at End of Period	$ 9,083	$ 9,013	$ 6,607