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Contingencies and commitments - Summary of aggregate amount of future payment commitments under purchase obligations outstanding (Detail) - USD ($) $ in Millions | Dec. 31, 2018 | Jan. 01, 2018
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Disclosure of future payment commitments under purchase obligations [Line Items] |  |
Aggregate amount of future payment commitments under purchase obligations outstanding | $ 17,050 | $ 19,480
Due within 1 year [member] |  |
Disclosure of future payment commitments under purchase obligations [Line Items] |  |
Aggregate amount of future payment commitments under purchase obligations outstanding | 2,804 | 2,874
Between 1 and 2 years [member] |  |
Disclosure of future payment commitments under purchase obligations [Line Items] |  |
Aggregate amount of future payment commitments under purchase obligations outstanding | 1,565 | 1,712
Between 2 and 3 years [member] |  |
Disclosure of future payment commitments under purchase obligations [Line Items] |  |
Aggregate amount of future payment commitments under purchase obligations outstanding | 1,344 | 1,401
Between 3 and 4 years [member] |  |
Disclosure of future payment commitments under purchase obligations [Line Items] |  |
Aggregate amount of future payment commitments under purchase obligations outstanding | 1,097 | 1,282
Between 4 and 5 years [member] |  |
Disclosure of future payment commitments under purchase obligations [Line Items] |  |
Aggregate amount of future payment commitments under purchase obligations outstanding | 882 | 1,026
More than 5 years [member] |  |
Disclosure of future payment commitments under purchase obligations [Line Items] |  |
Aggregate amount of future payment commitments under purchase obligations outstanding | $ 9,358 | $ 11,185

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- Definition Future Payment Commitments Under Purchase Obligations + References No definition available. + Details
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