Increase or decrease in performance stock units if performance is above or below level defined in agreement.

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Fair value of RSUs and PSUs granted.

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Performance share unit payout based upon certain performance metrics.

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- Definition

Amount of cost not yet recognized for nonvested award under share-based payment arrangement.

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Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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- Definition

Amount after tax of reclassification adjustments of other comprehensive income (loss) attributable to parent.

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Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition.

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The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

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- Definition

Weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect as a result of the occurrence of a terminating event.

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- Definition

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 weighted average fair value at grant date for nonvested equity-based awards issued 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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- Definition

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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Per share or unit weighted-average fair value of nonvested award under share-based payment arrangement. Excludes share and unit options.

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- Definition

The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

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The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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No definition available.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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No definition available.

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Intrinsic value of outstanding award under share-based payment arrangement. Excludes share and unit options.

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- Definition

Intrinsic value of vested award under share-based payment arrangement. Excludes share and unit options.

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No definition available.

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STOCKHOLDERS' EQUITY AND STOCK-BASED COMPENSATION STOCKHOLDERS' EQUITY AND STOCK-BASED COMPENSATION (Equity RSUs and PSUs) (Details) - USD ($) $ / shares in Units, $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percent Addition or Reduction In Restricted Stock Units If Performance Is Below Level Defined In Agreement		25.00%		25.00%
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding [Roll Forward]
Granted in period (number of RSUs and PSUs)		700,000	500,000	600,000
Performance Shares [Member] \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period		3 years
Performance Share Unit Payout		200.00%		175.00%
Performance Shares [Member] \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance Share Unit Payout		0.00%		0.00%
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period		3 years
Restricted Stock Units (RSUs) and Performance Share Units (PSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding [Roll Forward]
Balance at beginning of period (in number of RSUs and PSUs)		5,804,637
Granted in period (number of RSUs and PSUs)		2,135,224
Vested in Period (number of RSUs and PSUs)		(2,191,743)
Forfeited in Period (number of RSUs and PSUs)		(157,433)
Balance at end of period (in number of RSUs and PSUs)		5,590,685	5,804,637
Beginning Balance - weighted average grant date fair value		$ 19.97
Granted - Weighted average grant date fair value		11.13
Vested - weighted average grant date fair value		14.99
Forfeited - weighted average grant date fair value		17.58
Ending balance - weighted average grant date fair value		$ 18.61	$ 19.97
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value, Outstanding		$ 73
Fair value of RSUs and PSUs granted		24	$ 41	$ 32
Intrinsic value of RSUs and PSUs vested		26	14	45
Total unrecognized compensation cost related to unvested RSUs and PSUs expected to be recognized over a weighted-average period		$ 13
Weighted-average period used in calculating unrecognized compensation cost, RSUs and PSUs (in years)		1 year 8 months 12 days
Outside Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	1 year
Accumulated Defined Benefit Plans Adjustment, Net Gain (Loss) Attributable to Parent [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Reclassification from AOCI, Current Period, Net of Tax, Attributable to Parent		$ 0	$ 0	$ 5