Earnings Per Share (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Basic earnings per share:
Income from continuing operations attributable to common shareholders	$ 2.25	$ 2.07	$ 2.90	$ 3.02
Income from discontinued operations	$ 0.09	$ 0.08	$ 0.10	$ 0.22
Earnings per share - basic	$ 2.34	$ 2.15	$ 3.00	$ 3.24
Diluted earnings per share:
Income from continuing operations attributable to common shareholders	$ 2.24	$ 2.06	$ 2.88	$ 3.01
Income from discontinued operations	$ 0.08	$ 0.08	$ 0.10	$ 0.21
Earnings per share - diluted	$ 2.32	$ 2.14	$ 2.98	$ 3.22
Dilutive stock options and performance shares	733,000	462,000	680,000	472,000
Options to purchase shares of common stock outstanding excluded from computation of diluted earnings per share due to its antidilutive effect		175,333		322,333