Shareholders' Equity And Net Income Per Share Share Repurchase Program (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share Repurchase Program [Line Items]
Stock Repurchased During Period, Shares	4,667,193	9,481,946	14,581,705
Stock Repurchased, Average Price	$ 82.00	$ 66.93	$ 79.48
Stock Repurchased During Period, Value	$ 383	$ 635	$ 1,159
Share Repurchase Program April 2016
Share Repurchase Program [Line Items]
Stock Repurchase Program, Authorized Amount	1,500
Stock Repurchase Program, Remaining Authorized Repurchase Amount	989
Share Repurchase Program January 2015
Share Repurchase Program [Line Items]
Stock Repurchase Program, Authorized Amount	$ 1,500