Stock-based Compensation (Schedule Of Compensation) (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Stock-Based Compensation, Before Tax: [Abstract]
Stock options	$ 4	$ 4	$ 12	$ 12
Retention awards	16	13	50	45
Total stock-based compensation, before tax	24	17	66	57
Excess tax benefits from equity compensation plans	1	$ 16	18	$ 51
Employee Stock Purchase Program [Member]
Stock-Based Compensation, Before Tax: [Abstract]
ESPP	$ 4		$ 4

Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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Amount of cash outflow for realized tax benefit related to deductible compensation cost reported on the entity's tax return for equity instruments in excess of the compensation cost for those instruments recognized for financial reporting purposes.

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Amount of noncash expense for award of restricted stock or unit under share-based payment arrangement.

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Amount of noncash expense for share-based payment arrangement.

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Amount of noncash expense for option under share-based payment arrangement.

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