Income Taxes - Additional Information (Detail) (USD $)	12 Months Ended		12 Months Ended		9 Months Ended
	Dec. 31, 2011	Sep. 30, 2012	Dec. 31, 2011 Research and Development Credit Carryforwards	Dec. 31, 2011 Federal Tax	Sep. 30, 2012 Minimum	Sep. 30, 2012 Maximum
Income Taxes [Line Items]
Deferred tax asset	$ 1,800,000
Deferred tax asset valuation allowance	199,200,000
Unrecognized tax benefit	0	0
Tax years open to examination by major taxing jurisdictions					1997	2011
Federal tax net operating loss carryforward	315,600,000
Federal research and experimentation	57,200,000		7,200,000
State tax net operating loss carryforward	151,900,000
Federal tax NOLs				243,500,000
Federal research and experimentation and orphan drug credit carryforward				51,700,000
Restricted NOLs				72,100,000
Federal tax credits				$ 5,500,000