Share Data (Calculation Of Basic And Diluted Earnings Per Share) (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Earnings Per Share [Abstract]
Number of common share equivalent securities excluded from the diluted earnings per share calculation									2,300,000	4,000,000	5,100,000
Income (loss) from continuing operations attributable to common shareholders									$ 161,665	$ 13,172	$ (295)
Amount allocated to participating securities									(2,784)	(551)	(265)
Income (loss) from continuing operations attributable to common shareholders, net of amount allocated to participating securities									158,881	12,621	(560)
Income from discontinued operations, including gain on sale, attributable to common shareholders									121,725	36,207	23,511
Net income attributable to common shareholders, as adjusted									280,606	48,828	22,951
Income (loss) from continuing operations attributable to common shareholders, as adjusted - per share									$ 1.90	$ 0.17	$ (0.01)
Income from discontinued operations, including gain on sale, attributable to common shareholders									$ 1.45	$ 0.50	$ 0.34
Net income attributable to common shareholders, as adjusted - per share	$ 1.63	$ 0.36	$ 0.26	$ 1.10	$ 0.63	$ 0.16	$ (0.23)	$ 0.10	$ 3.35	$ 0.67	$ 0.33
Weighted average number of common shares outstanding - basic									83,772,000	72,756,000	68,608,000
Income allocated to common units from continuing operations									1,984	0	0
Income (loss) from continuing operations attributable to common shareholders, as adjusted									160,865	12,621	(560)
Net income attributable to common shareholders, as adjusted									$ 282,590	$ 48,828	$ 22,951
Income (loss) from continuing operations attributable to common shareholders, as adjusted - per share									$ 1.88	$ 0.17	$ (0.01)
Income from discontinued operations, including gain on sale, attributable to common shareholders - per share									$ 1.42	$ 0.49	$ 0.34
Net income attributable to common shareholders, as adjusted - per share	$ 1.60	$ 0.35	$ 0.26	$ 1.07	$ 0.62	$ 0.16	$ (0.23)	$ 0.10	$ 3.30	$ 0.66	$ 0.33
Common share options and share awards granted									647,000	706,000	0
Common units									1,137,000	0	0
Weighted average number of common shares outstanding - diluted									85,556,000	73,462,000	68,608,000