Restructuring Liabilities - Summary of Changes in Restructuring Liabilities (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2018 USD ($)
Restructuring Cost and Reserve [Line Items]
Balance at beginning of period	$ 5,335
Current period charges	247
Change in estimate	1,293
Payments and usage—net of accretion	(2,434)
Balance at end of period	4,441
Severance and Related Costs [Member]
Restructuring Cost and Reserve [Line Items]
Balance at beginning of period	4,835
Current period charges	247
Change in estimate	1,293
Payments and usage—net of accretion	(2,434)
Balance at end of period	3,941
Facility Closing Costs [Member]
Restructuring Cost and Reserve [Line Items]
Balance at beginning of period	500
Balance at end of period	$ 500