Introduction and Basis of Presentation - Changes in Allowance for Doubtful Accounts (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Receivables [Abstract]
Balance at beginning of year	$ 1,117	$ 857	$ 1,280
Addition to provision	1,011	940	452
Amounts written off, net of recoveries	(1,093)	(680)	(875)
Balance at ending of year	$ 1,035	$ 1,117	$ 857