Income Taxes - Summary of Effective Tax Rates Differ from Statutory Income Tax Rates (Detail)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Statutory income tax rate	(34.00%)	(34.00%)	(34.00%)
State income taxes	(6.80%)	(5.70%)	(3.70%)
Valuation allowance increase	35.90%	35.20%	37.80%
Effect of foreign operations		(1.30%)	(0.20%)
Change in unused net operating loss and credit carryforwards	3.70%	2.80%	(0.20%)
Nondeductible items	1.60%	3.90%	0.40%
Effective income tax rate, Total	0.40%	0.90%	0.10%