INCOME TAXES - EFFECTIVE INCOME TAX RECONCILIATION (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Business Acquisition [Line Items]
U.S. federal tax rate	21.00%	35.00%	35.00%
Income before income tax	$ (1,840)	$ 1,016	$ 585
Expected tax expense	(386)	213	123
Nondeductible expenses	9	9	9
State income taxes	(62)	36	21
Valuation allowance	18	0	0
Tax law changes	(93)	(9)	(7)
Other—net	(2)	(2)	2
Income tax (benefit) expense	$ (516)	$ 247	$ 148
Effective tax rate	28.00%	24.30%	25.30%

Effective Income Tax Rate Reconciliation, State and Local Income Sourcing, Amount

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Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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Amount of income (loss) from continuing operations before deduction of income tax expense (benefit) and income (loss) attributable to noncontrolling interest, and addition of income (loss) from equity method investments.

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Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to tax exempt income, equity in earnings (loss) of an unconsolidated subsidiary, minority noncontrolling interest income (loss), tax holiday, disposition of a business, disposition of an asset, repatriation of foreign earnings, repatriation of foreign earnings jobs creation act of 2004, increase (decrease) in enacted tax rate, prior year income taxes, increase (decrease) in deferred tax asset valuation allowance, and other adjustments.

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