Valuation and Qualifying Accounts (Detail) - Allowance for Doubtful Accounts - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Valuation And Qualifying Accounts Disclosure [Line Items]
Beginning Balance		$ 3,545	$ 3,546	$ 3,674
Deductions	[1]	(354)	(1)	(128)
Ending Balance		$ 3,191	$ 3,545	$ 3,546

[1] Consists of uncollectible accounts written off