Earnings Per Share (Tables)

12 Months Ended

Dec. 31, 2011

Earnings Per Share [Abstract]

Average Common Shares Outstanding Basic and Diluted

	Average Common Shares Outstanding
	2011	2010	2009
	(Millions)
Average shares outstanding	395.4	411.3	414.6
Participating securities	0.3	1.1	1.5
Basic	395.7	412.4	416.1
Dilutive effect of stock options	1.6	1.1	0.4
Dilutive effect of restricted share and restricted share unit awards	1.3	0.9	0.3
Diluted	398.6	414.4	416.8

Options Outstanding not Included in Computation of Diluted EPS

	2011		2010		2009
Average number of share equivalents (millions)	3.6		13.9		21.8
Weighted-average exercise price	$	71.49	$	66.00	$	64.12
Expiration date of options	2011 to 2021		2010 to 2020		2009 to 2019
Options outstanding at year-end (millions)	3.0		14.7		20.3