Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Line Items]
Effective tax rate of deferred tax assets	40.00%
(Decreased) increase in valuation allowances	$ 14,558,000	$ 16,645,000	$ (272,000)
Deferred tax asset	$ 0
Minimum [Member]
Income Tax Disclosure [Line Items]
Various tax years	2000
Maximum [Member]
Income Tax Disclosure [Line Items]
Various tax years	2015
State research and development [Member]
Income Tax Disclosure [Line Items]
Net operating loss carryforwards	$ 261,431,000
Net operating loss and tax credit carryforwards expiration date	2016
Deferred tax assets attributable to stock-based compensation deductions excess of book expense	$ 1,393,000
Research [Member] | State research and development [Member]
Income Tax Disclosure [Line Items]
Research and development tax credit carryforwards	8,319,000
Internal Revenue Service (IRS)[Member]
Income Tax Disclosure [Line Items]
Net operating loss carryforwards	368,164,000
Internal Revenue Service (IRS)[Member] | Research [Member]
Income Tax Disclosure [Line Items]
Research and development tax credit carryforwards	$ 10,731,000
Net operating loss and tax credit carryforwards expiration date	2020