Income Taxes (Income Taxes And Related Effective Tax Rates) (Detail) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Disclosure Income Taxes Income Taxes And Related Effective Tax Rates [Abstract]
Income (loss) before income taxes	$ (61)	$ (106)	$ (167)	$ (439)
Provision (benefit) for income taxes	$ 0	$ 0	$ 0	$ 0
Effective tax rate	0.00%	0.00%	0.00%	0.00%

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

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+ Details

- Definition

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

+ References + Details