Earnings and Dividends Per Share (Summary Of Calculation Of Basic And Diluted Earnings Per Share) (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Earnings Per Share [Abstract]
Income from continuing operations attributable to common stockholders	$ 19,076	$ 15,860	$ 33,904	$ 33,077
Income from discontinued operations	844	1,068	1,759	2,201
Net income attributable to common stockholders	$ 19,920	$ 16,928	$ 35,663	$ 35,278
Weighted Average Number of Shares Outstanding, Basic	27,876,176	27,792,834	27,871,120	27,784,469
Income from continuing operations per common share, basic	$ 0.68	$ 0.57	$ 1.22	$ 1.19
Discontinued operations per common share, basic	$ 0.03	$ 0.04	$ 0.06	$ 0.08
Net income per common share attributable to common stockholders	$ 0.71	$ 0.61	$ 1.28	$ 1.27
Weighted average common shares outstanding, diluted	27,876,176	27,792,834	27,871,120	27,784,469
Stock options, diluted	37,551	27,997	36,480	27,558
Average dilutive common shares outstanding	27,913,727	27,820,831	27,907,600	27,812,027
Income from continuing operations per common share	$ 0.68	$ 0.57	$ 1.21	$ 1.19
Discontinued operations per common share	$ 0.03	$ 0.04	$ 0.06	$ 0.08
Net income per common share attributable to common stockholders	$ 0.71	$ 0.61	$ 1.27	$ 1.27
Stock options with an exercise price in excess of the market price for our common shares	16,848	11,026	10,100	14,559
Common Stock, Dividends, Per Share, Declared	$ 0.735	$ 0.65	$ 1.43	$ 1.30