Description of Business and Accounting Policies - Calculation of Diluted Shares (Details) - shares shares in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accounting Policies [Abstract]
Shares used in computation of basic earnings per share	496	495	493	491	490	488	486	484	494	487	480
Total dilutive effect of outstanding stock awards									10	13	13
Shares used in computation of diluted earnings per share	505	504	503	502	501	501	500	498	504	500	493