Japan pension plans (Details) $ in Millions	1 Months Ended
	May 31, 2014 USD ($)	Sep. 30, 2016 USD ($)	Dec. 31, 2015 USD ($)	Mar. 29, 2013 item
Defined Benefit Plan Disclosure [Line Items]
Number of Defined Benefit Pension Plans | item				2
Employer contributions	$ 2.0
Conversion of plan, proceed from LAPIS	$ 0.3
Pension liability		$ 5.7	$ 5.1
Accrued and other current liabilities
Defined Benefit Plan Disclosure [Line Items]
Pension liability included in accrued and other current liabilities		$ 0.3	$ 0.1