Restructuring Activities - Additional Information (Detail) $ in Thousands			3 Months Ended		12 Months Ended
	Jan. 08, 2017 Employee	Oct. 03, 2016	Dec. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Restructuring Cost And Reserve [Line Items]
Reduction in headcount, percent		22.00%
Restructuring activity, announcement date					Oct. 03, 2016
Restructuring expenses			$ 4,901	$ 809	$ 9,521	$ 5,710
Restructuring activities, description					One-time employee termination benefits were comprised of severance, benefits and related costs, all of which resulted in cash expenditures during the third and fourth quarters of 2016.
January 2017 Corporate Restructuring [Member]
Restructuring Cost And Reserve [Line Items]
Reduction in headcount, percent	30.00%
Restructuring activity, announcement date					Jan. 08, 2017
Restructuring and related cost, number of expected employees after headcount reduction | Employee	80
January 2017 Corporate Restructuring [Member] | Discontinued Operations [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring expenses					$ 9,500
Stock-based Compensation Expense, Contractual Termination Benefits and One-time Employee Termination Benefits [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring expenses						$ 5,700
Contractual Termination Benefits [Member] | January 2017 Corporate Restructuring [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring expenses					$ 9,500
One-time Termination Benefits | January 2017 Corporate Restructuring [Member]
Restructuring Cost And Reserve [Line Items]
Severance payments payment period					1 year