Earnings Per Share Earnings Per Share (Details) - $ / shares shares in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Document Period End Date			Sep. 30, 2017
Document Fiscal Year Focus			2017
Basic weighted average shares outstanding	82.6	90.4	84.1	93.5
Diluted	$ 2.91	$ 2.28	$ 1.65	$ 2.05
Basic	$ 2.96	$ 2.32	$ 1.68	$ 2.07
Restricted Stock Units (RSUs) [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	0.7	0.2	0.8	0.2