Income Per Common Share (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Numerator (basic and diluted):
Income from continuing operations	$ 275	$ 163	$ 618	$ 481
Less: Allocation to unvested restricted stock awards	1	1	5	3
Income from continuing operations attributable to common shareholders	274	162	613	478
(Loss) income from discontinued operations, net	0	(37)	411	1
Less: Allocation to unvested restricted stock awards	0	0	3	0
(Loss) income from discontinued operations, net attributable to common shareholders	0	(37)	408	1
Net income attributable to common shareholders	$ 274	$ 125	$ 1,021	$ 479
Denominator:
Basic common shares (based upon weighted average) (in shares)	261	286	265	289
Add: Stock option dilution (in shares)	0	1	1	1
Diluted common shares (in shares)	261	287	266	290

Allocation To Unvested Restricted Stock Awards Discontinuing Operations

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Amount after tax of income (loss) from continuing operations attributable to the parent.

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Amount after tax of income (loss) from a discontinued operation attributable to the parent. Includes, but is not limited to, the income (loss) from operations during the phase-out period, gain (loss) on disposal, gain (loss) for reversal of write-down (write-down) to fair value, less cost to sell, and adjustments to a prior period gain (loss) on disposal.

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Additional shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of share based payment arrangements using the treasury stock method.

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Amount, after deduction of tax, noncontrolling interests, dividends on preferred stock and participating securities; of income (loss) available to common shareholders.

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Amount, after deduction of tax, noncontrolling interests, dividends on preferred stock and participating securities; of income (loss) from continuing operations available to common shareholders.

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Amount of undistributed earnings (loss) allocated to participating securities for the basic earnings (loss) per share or per unit calculation under the two-class method.

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