Share-Based Payments (Summary Of Activity Related To Stock Options) (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Number of Options, Outstanding at beginning of period	1,724,723	9,407,898	13,455,047
Number of Options, Granted	0	0	0
Number of Options, Exercised	(756,954)	(1,619,206)	(1,204,138)
Number of Options, Forfeited or Expired	0	(6,063,969)	(2,843,011)
Number of Options, Outstanding at end of period	967,769	1,724,723	9,407,898	13,455,047
Number of Options, Exercisable at end of period	967,769
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Weighted-Average Exercise Price, Outstanding at beginning of period	$ 6.86	$ 16.58	$ 19.37
Weighted-Average Exercise Price, Granted	0	0	0
Weighted-Average Exercise Price, Exercised	6.93	7.08	6.69
Weighted-Average Exercise Price, Forfeited or Expired	0	21.88	34.00
Weighted-Average Exercise Price, Outstanding at end of period	6.80	$ 6.86	$ 16.58	$ 19.37
Weighted-Average Exercise Price, Exercisable at end of period	$ 6.80
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Aggregate Intrinsic Value, at end of period	$ 10	$ 11	$ 35	$ 34
Aggregate intrinsic Value, Exercisable at end of period	$ 10
Weighted-Average Contractual Term (in years), Outstanding	9 months 29 days	1 year 8 months 26 days	1 year 18 days	1 year 9 months 29 days
Weighted-Average Contractual Term (in years), Exercisable	9 months 29 days

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The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan.

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For presentations that combine terminations, the number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan or that expired.

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Weighted average price of options that were either forfeited or expired.

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Net number of share options (or share units) granted during the period.

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Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding.

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Number of options outstanding, including both vested and non-vested options.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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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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Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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Number of fully vested and expected to vest exercisable options that may be converted into shares under option plan. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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Weighted average price at which option holders acquired shares when converting their stock options into shares.

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Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options.

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Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of vested portions of options outstanding and currently exercisable.

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Weighted average remaining contractual term for vested portions of options outstanding and currently exercisable or convertible, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Weighted average remaining contractual term for option awards outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Number of share options (or share units) exercised during the current period.

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