Summary of Information about Warrants Outstanding (Detail)	3 Months Ended
	Mar. 31, 2013
Class of Warrant or Right [Line Items]
Outstanding Warrants	3,093,676
Exercisable Warrants	3,093,676
$6.96
Class of Warrant or Right [Line Items]
Warrants Outstanding, Issue Date	Jan. 30, 2009
Exercise Price of warrants issued	6.96
Outstanding Warrants	1,819,567
Warrant expiration date	Jul. 30, 2014
Weighted Average Remaining Contractual Life (Years)	1 year 3 months 18 days
Exercisable Warrants	1,819,567
$8.70
Class of Warrant or Right [Line Items]
Warrants Outstanding, Issue Date	Jan. 30, 2009
Exercise Price of warrants issued	8.70
Outstanding Warrants	3,912
Warrant expiration date	Jan. 30, 2014
Weighted Average Remaining Contractual Life (Years)	8 months
Exercisable Warrants	3,912
$10.68
Class of Warrant or Right [Line Items]
Warrants Outstanding, Issue Date	Aug. 25, 2009
Exercise Price of warrants issued	10.68
Outstanding Warrants	1,270,197
Warrant expiration date	Aug. 31, 2014
Weighted Average Remaining Contractual Life (Years)	1 year 4 months 24 days
Exercisable Warrants	1,270,197