Earnings Per Share (Details) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Earnings Per Share [Abstract]
Weighted-average basic common shares outstanding (in shares)	175.8	175.5	175.7	175.4	175.7	175.3
Potential number of shares issuable under the Company's LTSIP (in shares)	0.3	0.8	0.4	0.8	0.4	0.8
Weighted-average diluted common shares outstanding (in shares)	176.1	176.3	176.1	176.2	176.1	176.1