Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Income Taxes [Line Items]
Net operating loss carryforwards	$ 96,215	$ 79,050
Research and development credit carryforwards	29,564	26,112
Net Operating loss Carryforwards resulting from excess tax deduction	10,200
Increase (decrease) in valuation allowance	49,200
Net Operating Loss Carryforwards
Income Taxes [Line Items]
Increase (decrease) in deferred tax assets		(11,200)
General Business Credits
Income Taxes [Line Items]
Increase (decrease) in deferred tax assets		$ (636)
Federal
Income Taxes [Line Items]
Net operating loss carryforwards	$ 251,000
Net operating loss carryforwards, expiration date	2034
Research and Development Credit
Income Taxes [Line Items]
Net operating loss carryforwards, expiration date	2034
Research and development credit carryforwards	$ 29,000