Earnings Per Common Share ("EPS") (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Net Income		$ 391	$ 206	$ 717	$ 289
Weighted-average common shares outstanding (for basic calculation)		298.0	303.0	299.0	302.0
Effect of dilutive share-based employee compensation		6.0	4.0	5.0	5.0
Weighted-average common and dilutive potential common shares outstanding (for diluted calculation)		304.0	307.0	304.0	307.0
Basic EPS		$ 1.31	$ 0.68	$ 2.39	$ 0.96
Diluted EPS		$ 1.29	$ 0.67	$ 2.35	$ 0.94
Unexercised employee stock options and stock appreciation rights (in millions) excluded from the diluted EPS computation	[1]	1.5	5.2	2.1	4.7

[1] These unexercised employee stock options and stock appreciation rights were not included in the computation of diluted EPS because to do so would have been antidilutive for the periods presented.