Restructuring Programs and Other Separation Costs - Schedule of Restructuring Program Activity (Detail) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2018
2018 Restructuring Program [Member]
Restructuring Cost And Reserve [Line Items]
Costs incurred	$ 3,800	$ 5,500
Severance and Other Employment Expenses [Member] | 2018 Restructuring Program [Member]
Restructuring Cost And Reserve [Line Items]
Costs incurred		5,548
Payments made		(1,577)
Liability, ending balance	3,971	3,971
Severance and Other Employment Expenses [Member] | 2017 Restructuring Program [Member]
Restructuring Cost And Reserve [Line Items]
Liability, beginning balance		1,234
Payments made		(1,040)
Liability, ending balance	$ 194	$ 194