Income Taxes - Reconciliation of Statutory Federal Income Tax Rate to Effective Tax Rate (Detail)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Federal statutory tax rate (percent)	34.00%	34.00%	34.00%
State tax (percent)	11.10%	6.90%	10.50%
Change in valuation allowance (percent)	45.90%	40.00%	44.00%
Permanent differences (percent)	5.40%	5.30%	4.60%
Tax credits (percent)	(6.20%)	(3.80%)	(4.40%)
Foreign rate impact (percent)	(0.60%)	(0.20%)	(0.10%)
Foreign tax withheld at source (percent)	1.50%	0.00%	0.00%
Other (percent)	2.80%	1.70%	(0.90%)
Total effective tax rate (percent)	3.70%	2.10%	(1.30%)