Earnings Per Share (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Basic earnings per share:
Income from continuing operations attributable to common shareholders (in dollars per share)	$ 1.12	$ 0.79	$ 1.06	$ 0.64
Income (loss) from discontinued operations (in dollars per share)		$ 0.01	$ (0.02)	$ 0.02
Earnings per share - basic (in dollars per share)	$ 1.12	$ 0.80	$ 1.04	$ 0.66
Diluted earnings per share:
Income from continuing operations attributable to common shareholders (in dollars per share)	$ 1.12	$ 0.78	$ 1.05	$ 0.64
Income (loss) from discontinued operations (in dollars per share)	$ (0.01)	$ 0.01	$ (0.01)	$ 0.01
Earnings per share - diluted (in dollars per share)	$ 1.11	$ 0.79	$ 1.04	$ 0.65
Dilutive stock options and performance shares	868,000	674,000	788,000	601,000