Summary of Stock Warrant Activities (Detail)	6 Months Ended
	Jun. 30, 2012
Class of Warrant or Right [Line Items]
Shares - beginning of period	3,922,953
Exercised
Cancelled
Shares - end of period	3,922,953
Weighted average exercise price - beginning of period	11.52
Exercised
Cancelled
Weighted average exercise price - end of period	11.52
Weighted average remaining contractual term - beginning of period	1 year 3 months 7 days
Weighted average remaining contractual term - end of period	9 months 7 days