Shareholders' Equity (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions |
3 Months Ended | 12 Months Ended | |
|---|---|---|---|
Dec. 31, 2020 |
Dec. 31, 2019 |
Sep. 30, 2020 |
|
| Equity, Class of Treasury Stock [Line Items] | |||
| Total Share Repurchase Cost | $ 165.3 | $ 231.8 | |
| Payments for share repurchase contracts | $ 46.4 | ||
| Cash received from share repurchase contracts | 47.5 | 0.0 | |
| Common Stock | |||
| Equity, Class of Treasury Stock [Line Items] | |||
| Payments for accrued repurchases of common stock | $ 7.4 | $ 8.7 | |
| Common Stock | |||
| Equity, Class of Treasury Stock [Line Items] | |||
| Shares repurchased | 1.7 | 2.2 | |
| Average price per share | $ 93.45 | $ 102.99 | |
| Total Share Repurchase Cost | $ 159.9 | $ 223.1 | |
| Common Stock | Other Current Liabilities | |||
| Equity, Class of Treasury Stock [Line Items] | |||
| Total Share Repurchase Cost | $ 2.0 | ||