Income Per Common Share (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Numerator (basic and diluted):
Net income	$ 240	$ 211	$ 356	$ 360
Less: Allocation to unvested restricted stock awards	2	1	2	3
Net income available to common shareholders	$ 238	$ 210	$ 354	$ 357
Denominator:
Basic common shares (based upon weighted average) (in shares)	289	306	291	308
Add: Stock option dilution (in shares)	1	3	1	3
Diluted common shares (in shares)	290	309	292	311

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

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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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