Pension, Postretirement and Postemployment Benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Components of net periodic benefit cost (recognized in our consolidated statements of income):
Payment amount			$ 10.3
Settlement			3.0
Pension plan | Pool Pension Plan
Funded status:
unfunded liability	$ 5.3	$ 6.7
Components of net periodic benefit cost (recognized in our consolidated statements of income):
Net periodic benefit cost	$ 0.8	$ 1.2	$ 1.1