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Goodwill - Additional Information (Detail) - USD ($) | 3 Months Ended | 12 Months Ended
--- | --- | ---
Sep. 30, 2017 | Dec. 31, 2017 | Dec. 31, 2016
Goodwill [Line Items] |  |  |
Additions due to acquisitions |  |  | $ 42,000,000
Impairment loss of goodwill | $ 0 | $ 0 |
Accumulated impairment losses, net |  | 102,000,000 | 102,000,000
Microcontrollers and Digital ICs Group (MDG) [Member] |  |  |
Goodwill [Line Items] |  |  |
Additions due to acquisitions |  |  | 42,000,000
Accumulated impairment losses, net |  | 96,000,000 | 96,000,000
Microcontrollers and Digital ICs Group (MDG) [Member] | NFC and RFID Reader Business [Member] |  |  |
Goodwill [Line Items] |  |  |
Additions due to acquisitions |  | 42,000,000 |
Others [Member] |  |  |
Goodwill [Line Items] |  |  |
Accumulated impairment losses, net |  | $ 6,000,000 | $ 6,000,000

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- Definition Amount of increase in asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized resulting from a business combination. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267 + Details
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