Valuation and Qualifying Accounts (Detail) - Allowance for Doubtful Accounts [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Valuation And Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	$ 17,810	$ 19,725	$ 20,608
Additions Charged to Costs and Expenses	5,208	3,231	4,898
Deductions	(4,822)	(5,146)	(5,781)
Balance at End of Period	$ 18,196	$ 17,810	$ 19,725