Derivative Financial Instruments Derivative Instruments Not Designated as Hedges Amount Recognized in Earnings (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Derivative Instruments, Gain (Loss) [Line Items]
Cross-currency swap agreements, net	$ 272	$ (809)	$ (2,490)	$ (3,667)
Other income/(loss), net [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Cross-currency swap agreements, net	272	(809)	(2,490)	(3,667)
Currency Swap [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Net gain (loss) on mark-to-market of the swaps		11,200		300
Intercompany GRail Loan [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Net gain (loss) for mark-to-market of the U.K. intercompany loan	3,000	$ (12,000)	(5,100)	$ (4,000)
Mark to Market [Member] | Currency Swap [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Net gain (loss) on mark-to-market of the swaps	$ (2,800)		$ 2,600