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							12 Months Ended			15 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012
Earnings Per Share [Abstract]
Income from continuing operations attributable to common stockholders	$ 28,139	$ 13,282	$ 15,859	$ 17,216	$ 16,668	$ 23,985	$ 15,537	$ 74,496	$ 73,192	$ 61,786	$ 17,002
Discontinued operations								16,235	7,940	7,635
Net income attributable to common stockholders	$ 41,105	$ 14,350	$ 16,927	$ 18,349	$ 18,808	$ 25,117	$ 19,093	$ 90,731	$ 81,132	$ 69,421	$ 18,114
Weighted Average Number of Shares Outstanding, Basic	27,848,002	27,830,311	27,792,834	27,776,104	27,729,560	27,708,136	27,696,727	27,811,813	27,719,096	27,664,482	27,741,961
Income from continuing operations per common share, basic	$ 1.01	$ 0.48	$ 0.57	$ 0.62	$ 0.60	$ 0.87	$ 0.56	$ 2.68	$ 2.64	$ 2.23	$ 0.61
Discontinued operations per common share, basic	$ 0.47	$ 0.04	$ 0.04	$ 0.04				$ 0.58	$ 0.29	$ 0.28
Net income per common share attributable to common stockholders								$ 3.26	$ 2.93	$ 2.51
Weighted average common shares outstanding, diluted								27,811,813	27,719,096	27,664,482
Stock options, diluted								26,907	72,035	65,548
Restricted shares, diluted								0	1,461	2,929
Average dilutive common shares outstanding	27,868,245	27,862,582	27,820,831	27,803,222	27,789,725	27,799,616	27,796,109	27,838,720	27,792,592	27,732,959	27,784,915
Income from continuing operations per common share	$ 1.01	$ 0.48	$ 0.57	$ 0.62	$ 0.60	$ 0.86	$ 0.56	$ 2.68	$ 2.63	$ 2.23	$ 0.61
Discontinued operations per common share	$ 0.47	$ 0.04	$ 0.04	$ 0.04	$ 0.08	$ 0.04	$ 0.13	$ 0.58	$ 0.29	$ 0.27	$ 0.04
Net income per common share attributable to common stockholders								$ 3.26	$ 2.92	$ 2.50
Stock options with an exercise price in excess of the market price for our common shares								0	16,758	1,297
Common Stock, Dividends, Per Share, Declared								$ 2.86	$ 2.715	$ 2.36