Income Taxes - Reconciliation of Federal Statutory Income Tax Rate and Effective Income Tax Rate (Detail)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Tax Disclosure [Abstract]
Federal statutory rate	34.00%	34.00%	34.00%
Change in valuation allowance	(2.50%)	(4.90%)	(0.20%)
State income taxes, net of federal effect	5.80%	5.80%	5.80%
Research and development credits	4.30%	1.50%	4.20%
Removal of net operating loss and other credits	(39.50%)	(36.40%)	(43.90%)
Other	(2.10%)	0.00%	0.10%
Effective income tax rate	0.00%	0.00%	0.00%