Stock Based Compensation - Unvested Stock Option Activity (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Forfeited, Shares	(55,710)	(124,710)	(177,321)
Granted - at fair market value, Weighted Average Exercise Price	$ 7.54	$ 3.76	$ 9.19
Unvested Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unvested shares, beginning of year	1,251,328	1,790,425	2,233,717
Vested, Shares	(533,118)	(679,387)	(822,471)
Forfeited, Shares	(55,710)	(124,710)	(177,321)
Unvested Shares, end of year	2,045,000	1,251,328	1,790,425
Unvested Weighted Average Exercise Price, beginning of year	$ 14.99	$ 13.50	$ 13.88
Vested, Weighted Average Exercise Price	$ 8.61	$ 14.76	$ 19.19
Forfeited, Weighted Average Exercise Price	$ 8.45	$ 10.13	$ 11.59
Unvested Weighted Average Exercise Price, end of year	$ 13.99	$ 14.99	$ 13.50
Options At Fair Market Value [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted - above fair market value, shares	1,382,500	265,000	376,500
Options At Fair Market Value [Member] | Unvested Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted - above fair market value, shares	1,382,500	265,000	376,500
Granted - at fair market value, Weighted Average Exercise Price	$ 7.54	$ 7.42	$ 8.99
Options Above Fair Market Value [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted - above fair market value, shares			180,000
Options Above Fair Market Value [Member] | Unvested Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted - above fair market value, shares			180,000
Granted - above fair market value, Weighted Average Exercise Price			$ 9.45