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
	Mar. 31, 2020	Mar. 31, 2019
Earnings Per Share [Abstract]
Net income from continuing operations	$ (319)	$ 375
Loss from discontinued operations, net of tax	0	(1)
Net income	$ (319)	$ 374
Basic weighted-average common shares outstanding	375,723	404,129
Diluted weighted-average common shares outstanding	375,723	405,959
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	1,800
Earnings Per Share, Basic [Abstract]
Net (loss) income from continuing operations, basic earnings per common share	$ (0.85)	$ 0.93
Net (loss) income, basic earnings per common share	(0.85)	0.93
Earnings Per Share, Diluted [Abstract]
Net (loss) income from continuing operations, diluted earnings per common share	(0.85)	0.92
Net (loss) income, diluted earnings per common share	$ (0.85)	$ 0.92