Valuation and Qualifying Accounts (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Allowance for Doubtful Accounts
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	$ 359	$ 252	$ 489
Additions Charged to Costs and Expenses	233	235	166
Deductions	97	128	403
Balance at End of Period	495	359	252
Valuation Allowance of Deferred Tax Assets
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	7,477	6,882	4,650
Additions Charged to Costs and Expenses	(870)	595	2,232
Deductions	0	0	0
Balance at End of Period	$ 6,607	$ 7,477	$ 6,882