Japan pension plans - (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Pension liability	$ 5.0	$ 4.8
Accrued and other current liabilities
Defined Benefit Plan Disclosure [Line Items]
Pension liability included in accrued and other current liabilities	$ 0.4	$ 0.4