Accounting Policies and Supplemental Disclosures - Calculation of Diluted Shares (Details) - shares shares in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Accounting Policies [Abstract]
Shares used in computation of basic earnings per share (in shares)	505	500	505	499
Total dilutive effect of outstanding stock awards (in shares)	9	9	9	9
Shares used in computation of diluted earnings per share (in shares)	514	509	514	508