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Goodwill and Other Intangible Assets (Tables) | 12 Months Ended
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Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract] |
Schedule of changes in the net carrying amount of goodwill by operating segment | The changes in the net carrying amount of goodwill for the years ended December 31, 2017 and 2016, respectively, are as follows (in millions):
Balance as of January 1, 2016 | $ | 7,068 |
Goodwill related to current year acquisitions | 642 |
Goodwill related to disposals | (34 | )
Goodwill related to prior year acquisitions | 4 |
Foreign currency translation | (270 | )
Balance as of December 31, 2016 | $ | 7,410 |
Goodwill related to current year acquisitions | 619 |
Goodwill related to disposals | (5 | )
Goodwill related to prior year acquisitions | (13 | )
Foreign currency translation | 347 |
Balance as of December 31, 2017 | $ | 8,358 |
Schedule of other intangible assets by asset class | Amortization basis and estimated useful lives by intangible asset type are generally as follows:
Intangible Asset Description |  | Amortization Basis |  | Expected Life
Customer related and contract based |  | In line with underlying cash flows |  | 7 to 20 years
Tradenames |  | Straight-line |  | 1 to 3 years
Technology |  | Straight-line |  | 5 to 7 years
Other intangible assets by asset class are as follows (in millions):
| As of December 31
| 2017 |  | 2016
| Gross Carrying Amount |  | Accumulated Amortization and Impairment |  | Net Carrying Amount |  | Gross Carrying Amount |  | Accumulated Amortization and Impairment |  | Net Carrying Amount
Customer related and contract based | 2,550 |  |  | 1,415 |  |  | 1,135 |  |  | 2,023 |  |  | 1,198 |  |  | 825 |
Tradenames (1) | 1,047 |  |  | 533 |  |  | 514 |  |  | 1,027 |  |  | 7 |  |  | 1,020 |
Technology and other (1) | 416 |  |  | 332 |  |  | 84 |  |  | 347 |  |  | 302 |  |  | 45 |
Total | $ | 4,013 |  |  | $ | 2,280 |  |  | $ | 1,733 |  |  | $ | 3,397 |  |  | $ | 1,507 |  |  | $ | 1,890 |
(1) | Prior to May 1, 2017, finite lived tradenames were classified within Technology and other. As of December 31, 2016, $29 million of gross carrying amount and $7 million of accumulated amortization related to finite-lived tradenames were reclassified from Technology and other to Tradenames.
Schedule of estimated future amortization expense on intangible assets | The estimated future amortization for finite-lived intangible assets as of December 31, 2017 is as follows (in millions):
2018 |  | $ | 410 |
2019 |  | 420 |
2020 |  | 253 |
2021 |  | 140 |
2022 |  | 98 |
Thereafter |  | 412 |
Total |  | $ | 1,733 |

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- Definition Tabular disclosure of goodwill by reportable segment and in total which includes a rollforward schedule. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13854-109267 + Details
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- Definition Tabular disclosure of the amount of amortization expense expected to be recorded in succeeding fiscal years for finite-lived intangible assets. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 30 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275 + Details
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