Summary of Warrant Activity (Detail)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Warrants Outstanding Shares
Warrants outstanding at beginning of the period	791,508	3,127,618	4,867,477
Exercised	(765,915)	(2,336,110)	(1,739,859)
Canceled or expired	(25,593)
Warrants outstanding at end of the period	0	791,508	3,127,618
Weighted Average Exercise Price
Warrants outstanding at beginning of the period	10.05	8.48	9.54
Exercised	10.12	7.96	11.81
Canceled or expired	7.92
Warrants outstanding at end of the period		10.05	8.48