Earnings Per Share Computation Of Basic And Diluted Earnings Per Common Share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Numerator:
Net income from continuing operations	$ 39,416	$ 38,573	$ 96,164	$ 89,973
Net income (loss) from discontinued operations	(51)	143	1,711	293
Net income	39,365	38,716	97,875	90,266
Denominator:
Basic earnings per share (in dollars per share)	$ 0.67	$ 0.66	$ 1.68	$ 1.54
Numerator:
Net income from continuing operations	39,416	38,573	96,164	89,973
Net income (loss) from discontinued operations	(51)	143	1,711	293
Net income	39,365	38,716	97,875	90,266
Denominator:
Diluted earnings per share (in dollars per share)	$ 0.67	$ 0.66	$ 1.66	$ 1.53
Basic earnings per share [Member]
Numerator:
Net income from continuing operations	39,416	38,573	96,164	89,973
Net income (loss) from discontinued operations	(51)	143	1,711	293
Net income	39,365	38,716	97,875	90,266
Income allocated to participating securities	(343)	(377)	(867)	(901)
Net income available to common shareholders, basic	39,022	38,339	97,008	89,365
Denominator:
Weighted average common shares outstanding – basic	57,932	57,978	57,878	57,884
Numerator:
Net income from continuing operations	39,416	38,573	96,164	89,973
Net income (loss) from discontinued operations	(51)	143	1,711	293
Net income	39,365	38,716	97,875	90,266
Income allocated to participating securities	(343)	(377)	(867)	(901)
Denominator:
Weighted average common shares outstanding – basic	57,932	57,978	57,878	57,884
Diluted earnings per share [Member]
Numerator:
Net income from continuing operations	39,416	38,573	96,164	89,973
Net income (loss) from discontinued operations	(51)	143	1,711	293
Net income	39,365	38,716	97,875	90,266
Income allocated to participating securities	(340)	(375)	(862)	(898)
Denominator:
Weighted average common shares outstanding – basic	57,932	57,978	57,878	57,884
Numerator:
Net income from continuing operations	39,416	38,573	96,164	89,973
Net income (loss) from discontinued operations	(51)	143	1,711	293
Net income	39,365	38,716	97,875	90,266
Income allocated to participating securities	(340)	(375)	(862)	(898)
Net income available to common shareholders, diluted	39,025	38,341	97,013	89,368
Denominator:
Weighted average common shares outstanding – basic	57,932	57,978	57,878	57,884
Diluted effect of stock options and PVRSUs	524	394	503	383
Weighted average common shares outstanding – diluted	58,456	58,372	58,381	58,267
Continuing operations [Member]
Denominator:
Basic earnings per share (in dollars per share)	$ 0.67	$ 0.66	$ 1.65	$ 1.54
Denominator:
Diluted earnings per share (in dollars per share)	$ 0.67	$ 0.65	$ 1.63	$ 1.53
Discontinued Operations [Member]
Numerator:
Net income (loss) from discontinued operations	(51)	143	1,711	293
Denominator:
Basic earnings per share (in dollars per share)	$ 0.00	$ 0.00	$ 0.03	$ 0.00
Numerator:
Net income (loss) from discontinued operations	$ (51)	$ 143	$ 1,711	$ 293
Denominator:
Diluted earnings per share (in dollars per share)	$ 0.00	$ 0.01	$ 0.03	$ 0.00