Schedule II, Valuation and Qualifying Accounts (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Allowance for doubtful accounts
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	$ 4,691	$ 4,923	$ 6,004
Charged to Costs and Expenses	5,808	1,103	4,501
Deductions	(6,177)	(1,335)	(5,582)
Balance at End of Year	4,322	4,691	4,923
Valuation allowance on deferred taxes
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	17,205	17,173	18,991
Charged to Costs and Expenses	58,255	32	517
Deductions	0	0	(2,335)
Balance at End of Year	$ 75,460	$ 17,205	$ 17,173