Earnings Per Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008
Basic EPS:
Net Income (Loss) from continuing operations, and share Amounts	$ 84,610	$ 46,475	$ (39,076)
Net Income (Loss) from continuing operations, and share Amounts, Shares	42,394,000	38,300,000	33,594,000
Less: Income (Loss) from continuing operations allocated to unvested shareholders	(1,598)	(879)
Income (Loss) from continuing operations allocated to common shares	83,012	45,596	(39,076)
Income (Loss) from continuing operations allocated to common shares, Shares	42,394,000	38,300,000	33,594,000
Income (Loss) from continuing operations allocated to common shares, per share amount	$ 1.96	$ 1.19	$ (1.16)
Dilutive Securities:
Plus: Income (Loss) from continuing operations allocated to unvested shareholders	1,598	879
Less: Income (Loss) from continuing operations re-allocated to unvested shareholders	0
Income from continuing operations, stock options, value	(1,589)	(874)
Stock Options, Shares	235,000	224,000
Diluted EPS:
Net Income (Loss) from continuing operations, and assumed share conversions	$ 83,021	$ 45,601	$ (39,076)
Net Income (Loss) from continuing operations, and assumed share conversions, Shares	42,629,000	38,524,000	33,594,000
Net Income (Loss) from continuing operations, and assumed share conversions, per share amount	$ 1.95	$ 1.18	$ (1.16)
Earnings Per Share (Textual) [Abstract]
Options to purchase, shares	1,375,281	1,361,779	1,289,194	1,119,469
Options to purchase, exercise price	$ 32.46	$ 29.67	$ 29.72
Stock options not included in the computation of diluted EPS	800,000	600,000	1,300,000
Employee restricted stock grants not included in the computation of Diluted EPS, maximum	200,000	100,000
Employee restricted stock outstanding, shares			700,000