Restructuring - Summary of Significant Restructuring Plan Activity Related To Employees And Other Charges (Detail) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2017 USD ($)	Sep. 30, 2017 USD ($)
Q3 2017 Restructuring Plan [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring liability, Beginning balance		$ 0
Restructuring expense and adjustments	$ 845	845
Cash payments		(838)
Restructuring liability, Ending balance	7	7
Cumulative costs to date, as of September 30, 2017	845	845
Total costs expected to be incurred, as of September 30, 2017	1,011	1,011
Q2 2017 Restructuring Plan [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring liability, Beginning balance		0
Restructuring expense and adjustments		1,301
Cash payments		(1,177)
Restructuring liability, Ending balance	124	124
Cumulative costs to date, as of September 30, 2017	1,301	1,301
Total costs expected to be incurred, as of September 30, 2017	1,436	1,436
Q2 2015 Restructuring Plan [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring liability, Beginning balance		19,388
Restructuring expense and adjustments	(100)	(560)
Cash payments		(3,890)
Restructuring liability, Ending balance	14,938	14,938
Cumulative costs to date, as of September 30, 2017	34,215	34,215
Total costs expected to be incurred, as of September 30, 2017	$ 34,215	$ 34,215