Estimated net loss and prior service credit (Details 4) $ in Millions	12 Months Ended
	Dec. 31, 2015 USD ($)
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, amortization of net gains (losses)	$ (6.2)
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, amortization of net gains (losses)	(1.5)
Defined benefit plan, amortization of net prior service cost (credit)	$ (1.4)