Income Taxes (Narrative) (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Income Taxes [Line Items]
Net loss before income taxes	$ (41,250,000)	$ (43,172,000)	$ (32,465,000)
Federal tax provision at statutory rate	35.00%	35.00%	35.00%
Income tax expense	(7,000)	4,331,000	(1,572,000)
Valuation allowance increased (decreased)	8,000,000	12,900,000	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 2032
Federal [Member]
Income Taxes [Line Items]
Operating loss carryforwards	274,600
Operating loss carryforwards, expiration dates	2031 and 2032
Unrealized net operating loss deductions from stock option exercises	100,200,000
Research and development credit and orphan drug credit	14,000,000
State [Member]
Income Taxes [Line Items]
Operating loss carryforwards	287,900,000
Operating loss carryforwards, expiration dates	At various dates between the years 2015 and 2032
Unrealized net operating loss deductions from stock option exercises	68,900,000
California Credit Carryforwards [Member]
Income Taxes [Line Items]
Research and development credit and orphan drug credit	$ 5,200,000