XML 81 R55.htm IDEA: XBRL DOCUMENT v3.8.0.1
Earnings Per Share Earnings Per Share (Details) - USD ($)
$ / shares in Units, $ in Millions
3 Months Ended 25 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Mar. 31, 2018
Earnings Per Share [Abstract]      
Target Achievement Percentage 100.00%    
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount 7,600,000 7,300,000  
Stock Repurchases [Line Items]      
Shares Repurchased and Retired During Period, Shares 3,700,000   20,200,000
Shares Repurchased and Retired During Period, Value $ 99    
Weighted Average Market Price of Shares Repurchased and Retired During Period $ 26.58   $ 28.36
Common Stock Settlement Date after Period End      
Stock Repurchases [Line Items]      
Shares Repurchased and Retired During Period, Shares 202,860