Employee plans - Expected Future Benefit Payments (Details) $ in Millions	Dec. 31, 2017 USD ($)
Pension Plans \| U.S. Plans
Gross Expected Payments
Expected future benefit payments, 2018	$ 364.4
Expected future benefit payments, 2019	361.4
Expected future benefit payments, 2020	359.3
Expected future benefit payments, 2021	357.6
Expected future benefit payments, 2022	355.1
Expected future benefit payments, 2023 - 2027	1,693.6
Pension Plans \| International Plans
Gross Expected Payments
Expected future benefit payments, 2018	98.7
Expected future benefit payments, 2019	102.8
Expected future benefit payments, 2020	106.9
Expected future benefit payments, 2021	110.3
Expected future benefit payments, 2022	117.5
Expected future benefit payments, 2023 - 2027	642.5
Other Postretirement Benefit Plans
Gross Expected Payments
Expected future benefit payments, 2018	12.7
Expected future benefit payments, 2019	10.5
Expected future benefit payments, 2020	10.0
Expected future benefit payments, 2021	9.4
Expected future benefit payments, 2022	8.8
Expected future benefit payments, 2023 - 2027	34.4
Gross Medicare Part D Receipts
Gross Medicare Part D Receipts, 2018	0.1
Gross Medicare Part D Receipts, 2019	0.0
Gross Medicare Part D Receipts, 2020	0.0
Gross Medicare Part D Receipts, 2021	0.0
Gross Medicare Part D Receipts, 2022	0.0
Gross Medicare Part D Receipts, 2023 - 2027	$ 0.0

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