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Revenue from Contracts with Customers - Contract Assets Rollforward (Details) - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2020 | Jun. 30, 2019 | Jun. 30, 2020 | Jun. 30, 2019
Capitalized Cost To Fulfill Customer Contracts |  |  |  |
Change in Capitalized Contract Costs |  |  |  |
Balance at beginning of period | $ 229 | $ 236 | $ 335 | $ 329
Additions | 274 | 336 | 592 | 682
Amortization | (313) | (357) | (729) | (796)
Impairment | 0 | 0 | 0 | 0
Foreign currency translation and other | 3 | 1 | (5) | 1
Balance at end of period | 193 | 216 | 193 | 216
Capitalized Cost To Obtain Customer Contracts |  |  |  |
Change in Capitalized Contract Costs |  |  |  |
Balance at beginning of period | 167 | 155 | 171 | 156
Additions | 16 | 17 | 28 | 26
Amortization | (11) | (11) | (23) | (22)
Impairment | 0 | 0 | 0 | 0
Foreign currency translation and other | 0 | 0 | (4) | 1
Balance at end of period | $ 172 | $ 161 | $ 172 | $ 161

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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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