Intangible assets and goodwill - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
Finite life intangible assets
Borrowings costs capitalized	$ 4.9	$ 2.8
Direct costs, selling, general and administration
Finite life intangible assets
Research and non-capitalizable development costs	109.4	95.4
Technologies, including development in-process
Finite life intangible assets
Borrowings costs capitalized	$ 4.9	$ 2.8
Minimum
Finite life intangible assets
Capitalization rate (as a percent)	3.40%	3.30%
Maximum
Finite life intangible assets
Capitalization rate (as a percent)	4.60%	3.80%

The amount of interest and other costs that an entity incurs in connection with the borrowing of funds that are directly attributable to the acquisition, construction or production of a qualifying asset and which form part of the cost of that asset.

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The weighted average of interest and other costs that an entity incurs in connection with the borrowing of funds applicable to the borrowings of the entity that are outstanding during the period, other than borrowings made specifically for the purpose of obtaining a qualifying asset. [Refer: Weighted average [member]; Borrowings]

+ References

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Line items represent concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes of the table.

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The amount of expenditure directly attributable to research or development activities, recognised in profit or loss.

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