v3.19.1

Long-Term Incentive Compensation / 401(k) Retirement Plan - Performance Share Units (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Recognition period of fair value as compensation cost	1 year
Performance Share Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards granted (in shares)	618,720	912,000
Number of shares outstanding (in shares)	1,508,760
Shares issued upon conversion (in shares)	1
Performance period	4 years
Vesting period	3 years
Number of shares subject to certain settlement and transfer restrictions (in shares)	1,224,000
Grant date fair value of awards	$ 5	$ 12
Unrecognized compensation cost	$ 9
Recognition period of fair value as compensation cost	3 years

Share-Based Compensation Arrangement By Share-Based Payment Award, Equity Instruments Other Than Options, Granted In Period, Fair Value

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Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Subject To Settlement And Transfer Restrictions, Number

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Number of shares issued for each share of convertible preferred stock that is converted.

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Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Unrecognized cost of unvested share-based awards, other than options, awarded to employees as compensation.

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Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

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