Income Taxes (Reconciliation of Provision for Income Taxes) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Taxes [Abstract]
Expected provision (benefit) at federal statutory rate	$ 113	$ 333	$ (935)
Increase (decrease) resulting from:
State income taxes, net of federal income tax effect	13	16	(79)
Rate impacts due to tax reform		370
Changes to valuation allowance due to tax reform		(370)
AMT tax reform impact - valuation allowance release		(68)
Change in uncertain tax positions		(5)	(19)
Change in valuation allowance	(121)	(364)	1,002
Removal of sequestration fee on AMT receivables	(5)
Other	1	(5)	2
Provision (Benefit) for Income Taxes	$ 1	$ (93)	$ (29)

Effective Income Tax Rate Reconciliation, Alternative Minimum Tax, Impact of Tax Reform, Amount

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Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance due to Tax Reform, Amount

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Effective Income Tax Rate Reconciliation, Change in Uncertain Tax Positions

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

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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 increase (decrease) in the valuation allowance for deferred tax assets.

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