Pension, Postretirement and Postemployment Benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
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	7.3	$ 8.4
Components of net periodic benefit cost (recognized in our consolidated statements of income):
Net periodic benefit cost	$ 1.1	$ 1.0	$ 0.3