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Shareholders' Equity (Share Repurchase) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions | 3 Months Ended | 12 Months Ended
--- | --- | ---
Dec. 31, 2015 | Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014
Class of Stock [Line Items] |  |  |  |
Aggregate purchase price |  | $ 499.0 | $ 237.3 | $ 487.7
Stock Repurchase Program Board Authorized Repurchases [Member] |  |  |  |
Class of Stock [Line Items] |  |  |  |
Shares repurchased (in shares) |  | 10.5 | 3.9 | 9.4
Aggregate purchase price |  | $ 497.0 | $ 235.1 | $ 485.1
Average purchase price per share (in dollars per share) |  | $ 47.30 | $ 60.49 | $ 51.59
Remaining amount available for share repurchase |  | $ 298.6 |  |
Treasury Shares Retirement [Member] |  |  |  |
Class of Stock [Line Items] |  |  |  |
Treasury Stock, Shares, Retired | 43.0 |  |  |

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- Definition Amount remaining of a stock repurchase plan authorized. + References No definition available. + Details
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- Definition Total cost of shares repurchased divided by the total number of shares repurchased. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 30 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6405813&loc=d3e23239-112655 + Details
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