Income Taxes - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Taxes [Line Items]
Provision for income taxes	$ 0	$ 0	$ 0
Increase in valuation allowance	11,100,000	8,800,000
Total unrecognized tax benefit	1,714,000	$ 1,194,000	$ 773,000	$ 388,000
Interest and penalties paid	0
Federal Income Tax
Income Taxes [Line Items]
Net operating loss	76,700,000
Research and development tax credit	2,400,000
State Income Tax
Income Taxes [Line Items]
Net operating loss	48,000,000
Research and development tax credit	$ 1,900,000