v3.8.0.1
Stock Plans (RSU Awards) (Details) - Restricted Stock Units (RSUs) [Member] - USD ($)
$ / shares in Units, $ in Millions
3 Months Ended 9 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Sep. 30, 2017
Sep. 30, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Number of Shares Granted (in shares)     1,209,230 1,212,600
Weighted-Average Grant Date Fair Value Per RSU Award Granted (in dollars per share)     $ 98.58 $ 89.03
Compensation expense for stock awards $ 24 $ 28 $ 84 $ 97