Earnings Per Share Computation Of Basic And Diluted Earnings Per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Numerator:
Net income from continuing operations	$ 35,813	$ 35,279	$ 57,407	$ 56,748
Net income from discontinued operations	0	121	0	1,762
Net income	$ 35,813	$ 35,400	$ 57,407	$ 58,510
Denominator:
Basic earnings per share - Continuing operations (in dollars per share)	$ 0.62	$ 0.61	$ 1.00	$ 0.97
Basic earnings per share - Discontinued operations (in dollars per share)	0.00	0.00	0.00	0.03
Basic earnings per share (in dollars per share)	$ 0.62	$ 0.61	$ 1.00	$ 1.00
Numerator:
Net income from continuing operations	$ 35,813	$ 35,279	$ 57,407	$ 56,748
Net income from discontinued operations	0	121	0	1,762
Net income	$ 35,813	$ 35,400	$ 57,407	$ 58,510
Denominator:
Diluted earnings per share - Continuing operations (in dollars per share)	$ 0.62	$ 0.60	$ 0.99	$ 0.96
Diluted earnings per share - Discontinued operations (in dollars per share)	0.00	0.00	0.00	0.03
Diluted earnings per share (in dollars per share)	$ 0.62	$ 0.60	$ 0.99	$ 0.99
Basic earnings per share [Member]
Numerator:
Net income from continuing operations	$ 35,813	$ 35,279	$ 57,407	$ 56,748
Net income from discontinued operations	0	121	0	1,762
Net income	35,813	35,400	57,407	58,510
Income allocated to participating securities	(243)	(324)	(413)	(523)
Net income available to common shareholders	$ 35,570	$ 35,076	$ 56,994	$ 57,987
Denominator:
Weighted average common shares outstanding – basic	57,212	57,893	57,108	57,850
Numerator:
Net income from continuing operations	$ 35,813	$ 35,279	$ 57,407	$ 56,748
Net income from discontinued operations	0	121	0	1,762
Net income	$ 35,813	$ 35,400	$ 57,407	$ 58,510
Denominator:
Weighted average common shares outstanding – basic	57,212	57,893	57,108	57,850
Diluted earnings per share [Member]
Numerator:
Net income from continuing operations	$ 35,813	$ 35,279	$ 57,407	$ 56,748
Net income from discontinued operations	0	121	0	1,762
Net income	$ 35,813	$ 35,400	$ 57,407	$ 58,510
Denominator:
Weighted average common shares outstanding – basic	57,212	57,893	57,108	57,850
Numerator:
Net income from continuing operations	$ 35,813	$ 35,279	$ 57,407	$ 56,748
Net income from discontinued operations	0	121	0	1,762
Net income	35,813	35,400	57,407	58,510
Income allocated to participating securities	(241)	(322)	(411)	(521)
Net income available to common shareholders	$ 35,572	$ 35,078	$ 56,996	$ 57,989
Denominator:
Weighted average common shares outstanding – basic	57,212	57,893	57,108	57,850
Diluted effect of stock options and PVRSUs	476	492	525	491
Weighted average common shares outstanding – diluted	57,688	58,385	57,633	58,341