Earnings Per Share (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Basic earnings per share:
Income from continuing operations attributable to common shareholders (in dollars per share)	$ 2.23	$ 2.25	$ 3.29	$ 2.90
Income (loss) from discontinued operations (in dollars per share)		$ 0.09	$ (0.01)	$ 0.10
Earnings per share - basic (in dollars per share)	$ 2.23	$ 2.34	$ 3.28	$ 3.00
Diluted earnings per share:
Income from continuing operations attributable to common shareholders (in dollars per share)	$ 2.21	$ 2.24	$ 3.26	$ 2.88
Income (loss) from discontinued operations (in dollars per share)		$ 0.08	$ (0.01)	$ 0.10
Earnings per share - diluted (in dollars per share)	$ 2.21	$ 2.32	$ 3.25	$ 2.98
Performance shares and restricted stock unit awards	1,100,000	733,000	971,000	680,000