Accounting Policies - Calculation of Diluted Shares (Details) - shares shares in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Accounting Policies [Abstract]
Shares used in computation of basic earnings per share	479	473	478	472
Total dilutive effect of outstanding stock awards	13	10	13	10
Shares used in computation of diluted earnings per share	492	483	491	482