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	$ 7,290	$ 7,533	$ 8,792
Charged to Income	1,799	1,693	1,178
Charged to Equity	0	0	0
Acquisition of business	0	3	0
Deductions	1,519	1,939	2,437
Balance at End of Year	7,570	7,290	7,533
Tax valuation allowance
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	20,228	15,103	33,303
Charged to Income	20,536	291	680
Charged to Equity	(2,828)	0	0
Acquisition of business	(1,057)	7,484	0
Deductions	6,777	2,650	18,880
Balance at End of Year	$ 30,102	$ 20,228	$ 15,103