Summary of Significant Accounting Policies Earnings Per Share (Details) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Antidilutive shares excluded from computation of EPS	0.3
Used in basic calculation	179.8	179.2	177.8
Potential number of shares issuable upon excerise of in-the-money stock options under the Long-term Stock Incentive Plan	0	0.3	0.9
Average diluted common shares outstanding (in shares)	179.8	179.5	178.7