Analysis of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deferred tax assets:
Net operating loss carryforwards	$ 212,342	$ 144,897
Difference in depreciation and amortization	55,162	1,210
Research and development tax credits	67,309	44,306
Stock-based compensation	15,538	14,392
Deferred rent	4,831	1,210
Deferred revenue	888	904
Capitalized inventory	22,943	22,127
Other	15,727	4,071
Total deferred tax assets	394,740	233,117
Deferred tax liabilities:
Debt discount	(25,162)	(28,548)
Total deferred tax liabilities	(25,162)	(28,548)
Valuation allowance	(369,345)	(204,569)
Net deferred tax assets	$ 233	$ 0