Debt (Details Textual) $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($) Instrument	Dec. 31, 2017 USD ($) Instrument	Dec. 31, 2016 USD ($)
Line of Credit Facility [Line Items]
Operating assets pledged as collateral for notes	$ 281.1
Other Short-term Borrowings	110.8	$ 4.3
Annual commitment fees	$ 2.0	$ 2.0	$ 1.5
Fixed charge coverage ratio	2.3
Minimum debt covenant fixed charge coverage ratio	1.2
Amount of secured debt available to be borrowed in accordance with public debt covenants	$ 1,444.5
Line of Credit US [Member]
Line of Credit Facility [Line Items]
Unsecured revolving credit facility	600.0
Rail Facility [Member]
Line of Credit Facility [Line Items]
Unsecured revolving credit facility	$ 250.0
Fair Value Hedging [Member]
Line of Credit Facility [Line Items]
Derivative, Number of Instruments Held | Instrument	9	10
Rail Facility [Member]
Line of Credit Facility [Line Items]
Unsecured revolving credit facility	$ 250.0