Summary of Restructuring Expenses by Function (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Restructuring Cost And Reserve [Line Items]
Total restructuring expenses, Cash	$ 2,524	$ 536	$ 2,760	$ 924
Total restructuring expenses, Non-cash		90		235
Total restructuring expenses	2,524	626	2,760	1,159
Research and Development [Member]
Restructuring Cost And Reserve [Line Items]
Total restructuring expenses, Cash	104	463	174	820
Total restructuring expenses, Non-cash		48		193
Total restructuring expenses	104	511	174	1,013
Selling, General and Administrative [Member]
Restructuring Cost And Reserve [Line Items]
Total restructuring expenses, Cash	2,420	73	2,586	104
Total restructuring expenses, Non-cash		42		42
Total restructuring expenses	$ 2,420	$ 115	$ 2,586	$ 146