Earnings per Share (Details) - shares shares in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Earnings Per Share [Abstract]
Basic weighted-average shares outstanding (in shares)	156.0	164.9	157.7	166.1
Effect of dilutive securities	3.0	1.8	3.2	1.7
Diluted weighted-average shares outstanding (in shares)	159.0	166.7	160.9	167.8
Anti-dilutive shares (less than) (in shares)	1.0	1.0	1.0	1.0