Accounting Policies and Supplemental Disclosures - Calculation of Diluted Shares (Details) - shares shares in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Accounting Policies [Abstract]
Shares used in computation of basic earnings per share (in shares)	501	495	500	493
Total dilutive effect of outstanding stock awards (in shares)	11	9	9	10
Shares used in computation of diluted earnings per share (in shares)	512	504	509	503