Derivative Financial Instruments Effect of Derivative Instruments Not Designated as Hedges (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Intercompany GRail Loan [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Foreign Currency Transaction Gain (Loss), Net of Tax	$ (10,400)	$ (10,800)	$ (3,900)
Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments not designated as hedges amount recognized in earnings	(5,679)	(5,956)	(3,267)
Currency Swap [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments not designated as hedges amount recognized in earnings	4,800	8,400	700
Interest (expense)/income | Currency Swap [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments not designated as hedges amount recognized in earnings	0	(3,505)	0
Other (expense)/income, net
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Foreign Currency Derivative Instruments Not Designated as Hedging Instruments, Net of Foreign Currency Transaction Gain (Loss) on Intercompany Loan	$ (5,679)	$ (2,451)	$ (3,267)