Earnings Per Share (Schedule of Basic and Diluted EPS ) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Numerator:
Net (loss) income	$ (61)	$ 726
Preferred stock dividends	(16)	(16)
Net (loss) income available to common stockholders	(77)	710
Income allocated to participating securities	(1)	(5)
Net (loss) income allocated to common stockholders	(78)	705
Income allocated to participating securities, diluted	(1)	(5)
Net income (loss) allocated to common stockholders, diluted	$ (78)	$ 705
Denominator:
Weighted-average shares of common stock outstanding	308	328
Weighted-average shares of common stock outstanding and common stock equivalents	308	328
Basic earnings (loss) per common share (in dollars per share)	$ (0.25)	$ 2.15
Diluted earnings (loss) per common share (in dollars per share)	$ (0.25)	$ 2.15