Accrued Restructuring Costs - Additional Information (Detail) (USD $)	3 Months Ended	9 Months Ended	12 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2011	Sep. 30, 2011	Dec. 31, 2010	Sep. 30, 2012 Facility Closing	Dec. 31, 2010 Facility Closing
Restructuring Cost and Reserve [Line Items]
Severance and related benefit costs			$ 6,500,000
Restructuring costs	$ 203,000	$ 62,000			$ 1,600,000
Lease expiration date				2013