Basis of Presentation and Consolidation (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Jan. 01, 2018	Dec. 31, 2017	Mar. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Decrease to retained earnings	$ (618,572)		$ (633,496)	$ (601,560)
Rail Group | Revenues under ASC 606 | Assets, Net
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Increase in net assetx		$ 26,000
Rail Group | Revenues under ASC 606 | Financing Obligations
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Increase in financing liabilities and deferred tax liabilities		34,000
ASC 606 Impact | Revenues under ASC 606
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Decrease to retained earnings		(8,429)
ASC 606 Impact | Rail Group | Revenues under ASC 606
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Decrease to retained earnings		$ 8,000