Restructuring - Additional Information (Detail) - USD ($)	9 Months Ended
	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014
Restructuring Cost and Reserve [Line Items]
Total restructuring charge	$ 16,700,000
Cost of revenue [Member]
Restructuring Cost and Reserve [Line Items]
Total restructuring charge	700,000
Research and development [Member]
Restructuring Cost and Reserve [Line Items]
Total restructuring charge	9,700,000
Sales and marketing [Member]
Restructuring Cost and Reserve [Line Items]
Total restructuring charge	800,000
General and administrative [Member]
Restructuring Cost and Reserve [Line Items]
Total restructuring charge	5,500,000
Q2 2015 Restructuring Plan [Member]
Restructuring Cost and Reserve [Line Items]
Total restructuring charge	12,600,000
Employee severance costs pay and related costs	10,600,000
Lease and contract termination costs	2,000,000
Stock-based expense reversals	400,000
Restructuring liability	$ 491,000	$ 1,860,000
Restructuring liability, expected paid out period	3 months 18 days
Q1 2015 Restructuring Plan [Member]
Restructuring Cost and Reserve [Line Items]
Total restructuring charge	$ 3,800,000
Employee severance costs pay and related costs	2,500,000
Lease and contract termination costs	1,300,000
Stock-based expense reversals	100,000
Restructuring liability	0		$ 330,000
Q1 2014 Restructuring Plan [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring liability	$ 5,205,000	6,663,000	8,082,000	$ 10,009,000
Restructuring liability, expected paid out period	1 year 3 months 18 days
Other Restructuring Plans [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring liability	$ 784,000	$ 1,933,000	$ 1,957,000	$ 2,857,000
Restructuring liability, expected paid out period	2 years 1 month 6 days