Restructuring Programs and Other Separation Costs - Schedule of Restructuring Program Activity (Detail) - Severance and Other Employment Expenses [Member] $ in Thousands	6 Months Ended
	Jun. 30, 2018 USD ($)
2018 Restructuring Program [Member]
Restructuring Cost And Reserve [Line Items]
Costs incurred	$ 1,750
Liability, ending balance	1,750
2017 Restructuring Program [Member]
Restructuring Cost And Reserve [Line Items]
Liability, beginning balance	1,234
Payments made	(807)
Liability, ending balance	$ 427