Computation of Basic/Diluted Earnings Per Common Share - Computation EPS (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended						9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019
Numerator:
Consolidated net income	$ 604	$ 580	$ 505	$ 204	$ 328	$ 447	$ 1,688	$ 978
Denominator:
Denominator for basic earnings per common share - weighted-average common shares outstanding (in shares)	772			767			771	766
Employee stock options and awards (in shares)	7			4			6	4
Denominator for diluted earnings per common share - weighted-average common shares outstanding plus dilutive common shares under treasury stock method (in shares)	779			771			777	770
Basic earnings per common share (in dollars per share)	$ 0.78			$ 0.27			$ 2.19	$ 1.28
Diluted earnings per common share (in dollars per share)	$ 0.78			$ 0.26			$ 2.17	$ 1.27