Stock Repurchases, Dividends and Earnings per Share - Share Repurchase Activity (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions |
3 Months Ended | 9 Months Ended | ||
|---|---|---|---|---|
Sep. 30, 2016 |
Sep. 30, 2015 |
Sep. 30, 2016 |
Sep. 30, 2015 |
|
| Equity [Abstract] | ||||
| Number of shares repurchased (in shares) | 2.2 | 2.3 | 6.5 | 7.3 |
| Amount paid | $ 110.5 | $ 93.8 | $ 306.6 | $ 293.3 |
| Weighted average cost per share (in dollars per share) | $ 50.75 | $ 40.89 | $ 47.83 | $ 40.66 |