Earnings Per Share Computation Of Basic And Diluted Earnings Per Common Share (Details) (USD $) Share data in Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Earnings Per Share [Line Items]
Net income from continuing operations	$ 38,573,000	$ 42,637,000	$ 89,973,000	$ 100,639,000
Net income from discontinued operations	143,000	107,000	293,000	270,000
Net income	38,716,000	42,744,000	90,266,000	100,909,000
Basic earnings per share (in dollars per share)	$ 0.66	$ 0.74	$ 1.54	$ 1.74
Diluted earnings per share (in dollars per share)	$ 0.66	$ 0.73	$ 1.53	$ 1.73
Continuing Operations [Member]
Earnings Per Share [Line Items]
Basic earnings per share (in dollars per share)	$ 0.66	$ 0.74	$ 1.54	$ 1.73
Diluted earnings per share (in dollars per share)	$ 0.65	$ 0.73	$ 1.53	$ 1.73
Discontinued Operations [Member]
Earnings Per Share [Line Items]
Net income from discontinued operations	143,000	107,000	293,000	270,000
Basic earnings per share (in dollars per share)	$ 0.00	$ 0.00	$ 0.00	$ 0.01
Diluted earnings per share (in dollars per share)	$ 0.01	$ 0.00	$ 0.00	$ 0.00
Basic earnings per share [Member]
Earnings Per Share [Line Items]
Net income from continuing operations	38,573,000	42,637,000	89,973,000	100,639,000
Net income from discontinued operations	143,000	107,000	293,000	270,000
Net income	38,716,000	42,744,000	90,266,000	100,909,000
Income allocated to participating securities	(377,000)	(453,000)	(901,000)	(1,066,000)
Net income available to common shareholders	38,339,000	42,291,000	89,365,000	99,843,000
Weighted average common shares outstanding - basic	57,978	57,388	57,884	57,455
Basic earnings per share (in dollars per share)	$ 0.66	$ 0.74	$ 1.54	$ 1.74
Diluted earnings per share [Member]
Earnings Per Share [Line Items]
Net income from continuing operations	38,573,000	42,637,000	89,973,000	100,639,000
Net income from discontinued operations	143,000	107,000	293,000	270,000
Net income	38,716,000	42,744,000	90,266,000	100,909,000
Income allocated to participating securities	(375,000)	(476,000)	(898,000)	(1,081,000)
Net income available to common shareholders	$ 38,341,000	$ 42,268,000	$ 89,368,000	$ 99,828,000
Weighted average common shares outstanding - basic	57,978	57,388	57,884	57,455
Diluted effect of stock options and PVRSUs	394	225	383	157
Weighted average shares outstanding - diluted	58,372	57,613	58,267	57,612