Accounting Policies and Supplemental Disclosures - Calculation of Diluted Shares (Details) - shares shares in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Accounting Policies [Abstract]
Shares used in computation of basic earnings per share	500	493	499	492
Total dilutive effect of outstanding stock awards	9	10	9	11
Shares used in computation of diluted earnings per share	509	503	508	503