XML 82 R65.htm IDEA: XBRL DOCUMENT v3.8.0.1
Shareholders' Equity (Share Repurchased Under Share Repurchase Program) (Details) - USD ($)
$ / shares in Units, shares in Millions, $ in Millions
 1 Months Ended 12 Months Ended
Nov. 30, 2017
Oct. 31, 2015
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Class of Stock [Line Items]          
Aggregate purchase price     $ 436.0 $ 499.0 $ 237.3
Treasury Stock, Shares, Retired 18.0 43.0      
Stock Repurchase Program Board Authorized Repurchases [Member]          
Class of Stock [Line Items]          
Shares repurchased (in shares)     10.1 10.5 3.9
Aggregate purchase price     $ 434.9 $ 497.0 $ 235.1
Average purchase price per share (in dollars per share)     $ 42.99 $ 47.30 $ 60.49
Remaining amount available for share repurchase     $ 113.7