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		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Numerator:
Net income from continuing operations	$ 41,419	$ 39,416	$ 98,826	$ 96,164
Net income from discontinued operations	0	(51)	0	1,711
Net income	$ 41,419	$ 39,365	$ 98,826	$ 97,875
Denominator:
Basic earnings per share - Continuing operations (in dollars per share)	$ 0.72	$ 0.67	$ 1.72	$ 1.65
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)	$ 0.72	$ 0.67	$ 1.72	$ 1.68
Numerator:
Net income from continuing operations	$ 41,419	$ 39,416	$ 98,826	$ 96,164
Net income from discontinued operations	0	(51)	0	1,711
Net income	$ 41,419	$ 39,365	$ 98,826	$ 97,875
Denominator:
Diluted earnings per share - Continuing operations (in dollars per share)	$ 0.72	$ 0.67	$ 1.71	$ 1.63
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)	$ 0.72	$ 0.67	$ 1.71	$ 1.66
Basic earnings per share [Member]
Numerator:
Net income from continuing operations	$ 41,419	$ 39,416	$ 98,826	$ 96,164
Net income from discontinued operations	0	(51)	0	1,711
Net income	41,419	39,365	98,826	97,875
Income allocated to participating securities	(278)	(343)	(695)	(867)
Net income available to common shareholders	$ 41,141	$ 39,022	$ 98,131	$ 97,008
Denominator:
Weighted average common shares outstanding – basic	56,843	57,932	57,019	57,878
Numerator:
Net income from continuing operations	$ 41,419	$ 39,416	$ 98,826	$ 96,164
Net income from discontinued operations	0	(51)	0	1,711
Net income	$ 41,419	$ 39,365	$ 98,826	$ 97,875
Denominator:
Weighted average common shares outstanding – basic	56,843	57,932	57,019	57,878
Diluted earnings per share [Member]
Numerator:
Net income from continuing operations	$ 41,419	$ 39,416	$ 98,826	$ 96,164
Net income from discontinued operations	0	(51)	0	1,711
Net income	$ 41,419	$ 39,365	$ 98,826	$ 97,875
Denominator:
Weighted average common shares outstanding – basic	56,843	57,932	57,019	57,878
Numerator:
Net income from continuing operations	$ 41,419	$ 39,416	$ 98,826	$ 96,164
Net income from discontinued operations	0	(51)	0	1,711
Net income	41,419	39,365	98,826	97,875
Income allocated to participating securities	(277)	(340)	(691)	(862)
Net income available to common shareholders	$ 41,142	$ 39,025	$ 98,135	$ 97,013
Denominator:
Weighted average common shares outstanding – basic	56,843	57,932	57,019	57,878
Diluted effect of stock options and PVRSUs	378	524	479	503
Weighted average common shares outstanding – diluted	57,221	58,456	57,498	58,381