Supplemental cash flow - (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Supplemental disclosures of cash flow information
Cash paid for interest	$ (152)	$ (41)	$ (30)
Income taxes refunds (payments)	1	1	(7)
Supplemental disclosures of non-cash investing and financing activities:
Accrued capital expenditures	22	18	$ 2
Acquisitions	$ 24	$ 1,197

Future cash outflow to pay for purchases of fixed assets that have occurred.

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The amount of cash paid during the current period to foreign, federal, state, and local authorities as taxes on income, net of any cash received during the current period as refunds for the overpayment of taxes.

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