Analysis of Deferred Tax Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Net operating loss carryforwards	$ 174,569	$ 138,786
Difference in depreciation and amortization	2,589	2,694
Research and development tax credits	37,812	31,397
Stock-based compensation	16,166	20,774
Deferred rent	2,306	2,771
Deferred revenue	1,315	1,324
Capitalized inventory	36,282	19,018
Other	3,047	3,060
Gross deferred tax assets	274,086	219,824
Valuation allowance	(274,086)	(219,824)
Net deferred tax assets	$ 0	$ 0