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Consolidated Statements of Equity (Parenthetical) - $ / shares
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Statement of Stockholders' Equity [Abstract]      
Issuance of common stock related to share based compensation (in shares) 456,252 783,793 807,015
Repurchase of common stock (in shares) 3,014,131 5,816,363 4,366,365
Repurchase of common stock, average price (in dollars per share) $ 150.77 $ 113.26 $ 111.62
Retirement of shares held in treasury (in shares) 8,000,000    
Retirement of shares held in treasury, average price (in dollars per share) $ 111.43