v3.10.0.1
Stock Repurchases, Dividends and Earnings per Share - Share Repurchase Activity (Details) - USD ($)
$ / shares in Units, shares in Millions, $ in Millions
3 Months Ended 6 Months Ended
Jun. 30, 2018
Jun. 30, 2017
Jun. 30, 2018
Jun. 30, 2017
Equity [Abstract]        
Number of shares repurchased (in shares) 3.3 2.1 7.1 3.7
Amount paid $ 219.5 $ 131.8 $ 474.0 $ 230.7
Weighted average cost per share (in dollars per share) $ 67.47 $ 62.87 $ 67.05 $ 61.81