Earnings Per Share (Details) (USD $) In Thousands, except Share data	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010	Dec. 31, 2010
Basic EPS:
Income from continuing operations	$ 26,682	$ 12,513	$ 46,931	$ 26,753
Income from continuing operations, Shares	42,436,000	37,845,000	42,313,000	37,749,000
Plus: Income from continuing operations allocated to unvested shareholders	(456)	(242)	(807)	(512)
Income from continuing operations allocated to common shares	26,226	12,271	46,124	26,241
Income from continuing operations allocated to common shares, Shares	42,436,000	37,845,000	42,313,000	37,749,000
Income from continuing operations allocated to common shares, per share amount	$ 0.62	$ 0.32	$ 1.09	$ 0.70
Dilutive Securities:
Less: Income from continuing operations allocated to unvested shareholders	456	242	807	512
Less: Income from continuing operations reallocated to unvested shareholders	(454)	(241)	(803)	(509)
Stock Options, Shares	229,000	258,000	219,000	230,000
Diluted EPS:
Income from continuing operations allocated to common shares, and assumed share conversions	$ 26,228	$ 12,272	$ 46,128	$ 26,244
Income from continuing operations allocated to common shares, and assumed share conversions, Shares	42,665,000	38,103,000	42,532,000	37,979,000
Income from continuing operations allocated to common shares, and assumed share conversions, per share amount	$ 0.61	$ 0.32	$ 1.08	$ 0.69
Earnings Per Share (Textuals) [Abstract]
Options to purchase, shares	1,383,331	1,500,000	1,383,331	1,500,000	1,361,779
Options to purchase, exercise price	$ 32.39	$ 29.18	$ 32.39	$ 29.18
Stock options not included in the computation of diluted EPS	600,000	1,200,000	800,000	1,200,000