|**Long-Term Debt And Lease Obligation (Tables)**                | 12 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
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|**Long-Term Debt and Lease Obligation [Abstract]**              |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
|Book Value And Principal Amounts Of Long-Term Debt              | This table summarizes the principal amounts of our long-term debt excluding unamortized discounts, none of which are encumbered by rating triggers:(Dollars in millions)Book valuePrincipal amountInterest rateYear of issueAt December 31,At December 31,20222021202220216.900%1998Senior debentures, due 2028$27$27$28$286.920%2005Senior debentures, due 20283913913913916.125%2004Senior notes, due 2034371371374374Total$789$789$793$793                                                                                                             
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|(Dollars in millions)                                           |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
|Interest rate                                                   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
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|6.900%                                                          |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
|6.920%                                                          |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
|6.125%                                                          |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
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|Lease Obligations Over Next Five Years and Thereafter           | interest for finance and operating leases:(Dollars in millions)Years ended December 31,202320242025202620272028 and thereafterFinance lease obligations$16$12$8$6$3$2Operating lease obligations222111Total lease obligations$18$14$10$7$4$3                                                                                                                                                                                                                                                                                                              
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|(Dollars in millions)                                           | Years ended December 31,                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  
|                                                                | 2023                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      
|Finance lease obligations                                       | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         
|Operating lease obligations                                     | 2                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         
|Total lease obligations                                         | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         
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|Other Operating and Finance Lease Disclosure [Table Text Block] | The following table provides lease cost and other information:(Dollars in millions)Years ended December 31,202220212020Lease cost:Finance lease cost$14$15$15Operating lease cost544Total lease cost$19$19$19Other information finance leases:Finance cash outflows$15$15$15Weighted average discount rate3.20%2.46%2.62%Weighted average remaining lease term in years3.493.453.67Other information operating leases:Operating cash outflows$4$4$8Weighted average discount rate3.44%2.86%3.65%Weighted average remaining lease term in years4.534.374.84
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|(Dollars in millions)                                           |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
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|Lease cost:                                                     |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
|Finance lease cost                                              |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
|Operating lease cost                                            |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
|Total lease cost                                                |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
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|Other information finance leases:                               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
|Finance cash outflows                                           |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
|Weighted average discount rate                                  |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
|Weighted average remaining lease term in years                  |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
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|Other information operating leases:                             |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
|Operating cash outflows                                         |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
|Weighted average discount rate                                  |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
|Weighted average remaining lease term in years                  |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
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X- DefinitionLease Obligations Over Next Five Years and Thereafter contains lease obligation expected to be paid over next five years and thereafter and includes finance and operating leases.
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