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Revenue from Contracts with Customers - Contract Assets Rollforward (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2020 | Dec. 31, 2019
Capitalized Cost To Fulfill Customer Contracts |  |
Change in Capitalized Contract Costs |  |
Balance at beginning of period | $ 335 | $ 329
Additions | 1,360 | 1,453
Amortization | (1,360) | (1,447)
Impairment | 0 | 0
Foreign currency translation and other | 4 | 0
Balance at end of period | 339 | 335
Capitalized Cost To Obtain Customer Contracts |  |
Change in Capitalized Contract Costs |  |
Balance at beginning of period | 171 | 156
Additions | 61 | 58
Amortization | (47) | (44)
Impairment | 0 | 0
Foreign currency translation and other | (1) | 1
Balance at end of period | $ 184 | $ 171

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- Definition Amount of amortization expense for asset recognized from cost incurred to obtain or fulfill contract with customer. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 340 -SubTopic 40 -Section 50 -Paragraph 3 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=68051541&loc=SL49131252-203054 + Details
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- Definition Amount of impairment loss for asset recognized from cost incurred to obtain or fulfill contract with customer. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 340 -SubTopic 40 -Section 50 -Paragraph 3 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=68051541&loc=SL49131252-203054 + Details
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- Definition Amount, after accumulated amortization and accumulated impairment loss, of asset recognized from cost incurred to obtain or fulfill contract with customer. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 340 -SubTopic 40 -Section 50 -Paragraph 3 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=68051541&loc=SL49131252-203054 + Details
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