Restructuring Programs and Separation Costs - Schedule of Restructuring Program Activity (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Restructuring Cost And Reserve [Line Items]
Restructuring and other related costs	$ 5,200	$ 9,016	$ 2,268
Severance and Other Employment Expenses [Member]
Restructuring Cost And Reserve [Line Items]
Liability, beginning balance	7,842
Restructuring and other related costs	5,200
Reduction in estimated expenses	(572)
Payments made	(11,236)
Liability, ending balance	1,234	7,842
2016 Restructuring Program [Member] | Severance and Other Employment Expenses [Member]
Restructuring Cost And Reserve [Line Items]
Liability, beginning balance	7,842
Reduction in estimated expenses	(572)
Payments made	(7,270)
Liability, ending balance		$ 7,842
2017 Restructuring Program [Member] | Severance and Other Employment Expenses [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring and other related costs	5,200
Payments made	(3,966)
Liability, ending balance	$ 1,234