Schedule II - Consolidated Valuation and Qualifying Accounts (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Allowance for doubtful accounts
Valuation And Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	$ 2,550	$ 3,040	$ 3,100
Charged/(Credited) to Expense	1,115	815	492
Other Adjustments	(41)	79	56
Deductions	(1,058)	(1,384)	(608)
Balance at End of Period	$ 2,566	2,550	3,040
Deferred tax valuation allowance
Valuation And Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period		1,206	1,361
Charged/(Credited) to Expense		$ (1,206)	(155)
Balance at End of Period			$ 1,206