Derivative Financial Instruments Cross Currency Swap (Details) $ in Thousands, € in Millions, AUD in Millions		3 Months Ended		6 Months Ended
	Dec. 22, 2016 AUD	Jun. 30, 2017 USD ($)	Jun. 30, 2016 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2016 USD ($)	Dec. 22, 2016 EUR (€)	Dec. 01, 2016 AUD
Currency Swap [Member]
Derivative [Line Items]
Notional Amount | €						€ 171.7
Expiration Date		Jun. 30, 2019
Currency Swap 1 [Member]
Derivative [Line Items]
Notional Amount	AUD 123.9					85.5
Currency Swap 2 [Member]
Derivative [Line Items]
Notional Amount	AUD 125.0					€ 86.3
BBR Interest rate [Member] | Currency Swap 1 [Member]
Derivative [Line Items]
Derivative, Description of Terms	Australian dollar BBR plus 4.50%
BBR Interest rate [Member] | Currency Swap 2 [Member]
Derivative [Line Items]
Derivative, Description of Terms	Australian dollar BBR plus 4.50%
EURIBOR Interest Rate [Member] | Currency Swap 1 [Member]
Derivative [Line Items]
Derivative, Description of Terms	EURIBOR plus 2.68%
EURIBOR Interest Rate [Member] | Currency Swap 2 [Member]
Derivative [Line Items]
Derivative, Description of Terms	EURIBOR plus 2.90%
Intercompany GRail Loan [Member]
Derivative [Line Items]
Debt Instrument, Face Amount | AUD							AUD 248.9
Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Gain (Loss) on Foreign Currency Derivative Instruments Not Designated as Hedging Instruments, Net of Foreign Currency Transaction Gain (Loss) on Intercompany Loan		$ (809)	$ 0	$ 3,667	$ 0
Other Nonoperating Income (Expense) [Member] | Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Gain (Loss) on Foreign Currency Derivative Instruments Not Designated as Hedging Instruments, Net of Foreign Currency Transaction Gain (Loss) on Intercompany Loan		$ (809)	$ 0	$ 3,667	$ 0