Summary of Warrant Activity (Detail)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Warrants Outstanding Shares
Warrants outstanding at beginning of year	4,867,477	4,944,241	5,388,833
Granted	0	0	0
Exercised	(1,739,859)	(76,764)	(51,333)
Expired	0	0	(393,259)
Warrants outstanding at end of year	3,127,618	4,867,477	4,944,241
Exercisable at end of year	3,127,618	4,867,477	4,944,241
Weighted Average Exercise Price
Warrants outstanding at beginning of year	9.54	9.48	20.40
Granted	0	0	0
Exercised	11.81	8.34	10.68
Expired	0.00	0.00	159.00
Warrants outstanding at end of year	8.48	9.54	9.48
Exercisable at end of year	8.48	9.54	9.48