Summary of Significant Accounting Policies (Earnings Per Share) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Basic earnings per share:
Income from operations attributable to common shareholders	$ 183	$ 278
Participating securities dividends	0	0
Net income available for common stock	$ 183	$ 278
Weighted average common shares outstanding (in shares)	363,000,000	326,000,000
Basic earnings per share - continuing operations (in dollars per share)	$ 0.50	$ 0.85
Diluted earnings per share:
Income from operations attributable to common shareholders	$ 183	$ 278
Participating securities dividends	0	0
Net income available for common stock	183	278
Income impact of assumed conversions	0	0
Net income available to common shareholders and assumed conversions	$ 183	$ 278
Weighted average common shares outstanding (in shares)	363,000,000	326,000,000
Incremental shares from assumed conversions (in shares)	1,000,000	1,000,000
Adjusted weighted average shares - diluted (in shares)	364,000,000	327,000,000
Diluted earnings per share - continuing operations (in dollars per share)	$ 0.50	$ 0.85
Stock option awards
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Stock-based compensation awards excluded from the computation of diluted earnings per share (in shares)	3,362,329	7,719,306