Income Taxes - Income Tax Expense (Benefit) Differed from Amounts Computed by Applying Statutory Federal Income Tax Rate (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Income tax provision at statutory rate	$ (15,662)	$ (17,013)	$ (9,955)
Nondeductible items	401	456	(32)
Change in tax credits	(792)	(678)	(893)
Change in valuation allowance	16,706	17,911	10,965
Foreign tax and other	(487)	(676)	(85)
Income tax expense (benefit)	$ 166	$ 0	$ 0