Recent accounting pronouncements and accounting changes (Details) - ASU No. 2014-09 $ in Millions	Jan. 01, 2018 USD ($)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect adjustment, increase in accumulated deficit	$ 21.4
Accumulated Deficit
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect adjustment, increase in accumulated deficit	$ 21.4

Amount after tax of increase (decrease) to equity or (increase) decrease to net assets, resulting from the cumulative effect adjustment of a new accounting principle applied in the period of adoption.

No definition available.

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Balance Type:	credit
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