Restructuring Activity Recorded in Operating Expenses and Accrued Expenses (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Restructuring Cost And Reserve [Line Items]
Restructuring amounts accrued, beginning balance	$ 357
Restructuring amounts accrued, ending balance		$ 357
Employee Severance
Restructuring Cost And Reserve [Line Items]
Restructuring amounts accrued, beginning balance	357
Restructuring expense incurred		3,560
Restructuring amounts paid	$ (357)	(3,203)
Restructuring amounts accrued, ending balance		$ 357