Summary of Information about Warrants Outstanding (Detail)					12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2012 $6.96	Dec. 31, 2012 $8.70	Dec. 31, 2012 $10.68
Class of Warrant or Right [Line Items]
Warrants Outstanding, Issue Date					Jan. 30, 2009	Jan. 30, 2009	Aug. 25, 2009
Exercise Price of warrants issued					6.96	8.70	10.68
Outstanding Warrants	3,127,618	4,867,477	4,944,241	5,388,833	1,842,551	3,912	1,281,155
Warrant expiration date					Jul. 30, 2014	Jan. 30, 2014	Aug. 31, 2014
Weighted Average Remaining Contractual Life (Years)					1 year 7 months 6 days	1 year 1 month 6 days	1 year 8 months 12 days
Exercisable Warrants	3,127,618	4,867,477	4,944,241		1,842,551	3,912	1,281,155