Income Taxes - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Taxes [Line Items]
Net loss before income taxes	$ (42,498,000)	$ (41,250,000)	$ (43,172,000)
Federal tax provision at statutory rate	35.00%	35.00%	35.00%
Income tax expense	(115,000)	(7,000)	4,331,000
Valuation allowance increased (decreased)	22,100,000	8,000,000	12,900,000
Gross unrecognized tax that would decrease effective tax rate, if recognized	600,000	600,000
Research and development credit and orphan drug credit, expiration dates	2024 through 2033
Federal [Member]
Income Taxes [Line Items]
Operating loss carryforwards	334,400,000
Operating loss carryforwards, expiration dates	2031 and 2033
Unrealized net operating loss deductions from stock option exercises	134,100,000
Research and development credit and orphan drug credit	22,200,000
State [Member]
Income Taxes [Line Items]
Operating loss carryforwards	268,000,000
Operating loss carryforwards, expiration dates	At various dates between the years 2015 and 2033
Unrealized net operating loss deductions from stock option exercises	63,400,000
California credit carryforwards [Member]
Income Taxes [Line Items]
Research and development credit and orphan drug credit	$ 7,800,000