Earnings Per Share (Details) In Millions, unless otherwise specified	3 Months Ended	6 Months Ended	12 Months Ended
Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Earnings Per Share [Abstract]
Weighted-average basic common shares outstanding (in shares)	175.5	177.2	175.4	177.8	175.3	177.7
Potential number of shares issuable under the Company's LTSIP (in shares)	0.8	1.1	0.8	1.1	0.8	1.2
Weighted-average diluted common shares outstanding (in shares)	176.3	178.3	176.2	178.9	176.1	178.9

The average number of shares or units issued and outstanding that are used in calculating diluted EPS or earnings per unit (EPU), determined based on the timing of issuance of shares or units in the period.

+ References+ Details

Number of [basic] shares or units, after adjustment for contingently issuable shares or units and other shares or units not deemed outstanding, determined by relating the portion of time within a reporting period that common shares or units have been outstanding to the total time in that period.

+ References

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Reference 3: http://www.xbrl.org/2003/role/presentationRef

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Reference 4: http://www.xbrl.org/2003/role/presentationRef

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Reference 5: http://www.xbrl.org/2003/role/presentationRef

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Reference 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

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+ Details