Earnings per Common Share (Schedule of Basic and Diluted Earnings per Common Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Earnings Per Share [Abstract]
Net income (loss) from continuing operations	$ 242	$ 584	$ (77)	$ 959
Loss from discontinued operations, net of tax	(1)	(2)	(1)	(3)
Net income (loss)	$ 241	$ 582	$ (78)	$ 956
Basic weighted-average common shares outstanding	375,051	398,100	375,387	401,098
Diluted weighted-average common shares outstanding	375,762	399,916	375,387	402,921
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	2,300	0	2,400	0
Earnings Per Share, Basic [Abstract]
Net income (loss) from continuing operations, basic earnings per common share	$ 0.65	$ 1.47	$ (0.20)	$ 2.39
Loss from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Basic Share	0	0	0	(0.01)
Net income (loss), basic earnings per common share	0.64	1.46	(0.21)	2.39
Earnings Per Share, Diluted [Abstract]
Net income (loss) from continuing operations, diluted earnings per common share	0.64	1.46	(0.20)	2.38
Loss from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Diluted Share	0	0	0	(0.01)
Net income (loss), diluted earnings per common share	$ 0.64	$ 1.46	$ (0.21)	$ 2.37