Income Taxes (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Income Taxes
(Benefit from) provision for income taxes (less than)	$ (88,000)	$ 59,000	$ 31,000	$ 76,000
Recognition of previously unrecognized tax benefit	200,000		200,000
Current income tax expense (benefit)
Current federal income tax expense (benefit)		0		0
Current state income tax expense (benefit)		0		0
Components of deferred tax assets and liabilities
Gross unrecognized tax benefits	$ 0		$ 0		$ 200,000
Maximum | Foreign
Income Taxes
(Benefit from) provision for income taxes (less than)		$ 100,000		$ 100,000