Restructuring Programs and Other Separation Costs - Schedule of Restructuring Program Activity (Detail) - Severance and Other Employment Expenses [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Restructuring Cost And Reserve [Line Items]
Liability, beginning balance	$ 1,234	$ 7,842
Costs incurred	5,548	5,200
Reduction in estimated expenses		(572)
Payments made	(6,245)	(11,236)
Liability, ending balance	537	1,234
2016 Restructuring Program [Member]
Restructuring Cost And Reserve [Line Items]
Liability, beginning balance		7,842
Reduction in estimated expenses		(572)
Payments made		(7,270)
2017 Restructuring Program [Member]
Restructuring Cost And Reserve [Line Items]
Liability, beginning balance	1,234
Costs incurred		5,200
Payments made	(1,234)	(3,966)
Liability, ending balance		$ 1,234
2018 Restructuring Program [Member]
Restructuring Cost And Reserve [Line Items]
Costs incurred	5,548
Payments made	(5,011)
Liability, ending balance	$ 537