Income Taxes (Details 3) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred tax liabilities:
Property, plant and equipment and Rail Group assets leased to others	$ (129,876)	$ (179,250)
Equity method investments	(31,223)	(45,244)
Other	(8,754)	(22,286)
Deferred tax liabilities	(169,853)	(246,780)
Deferred tax assets:
Employee benefits	15,229	25,403
Accounts and notes receivable	2,317	2,964
Inventory	6,100	9,979
Federal income tax credits	10,225	7,150
Net operating loss carryforwards	5,753	3,322
Other	9,674	16,224
Total deferred tax assets	49,298	65,042
Valuation allowance	(1,024)	(310)
Net deferred tax assets	48,274	64,732
Net deferred tax liabilities	$ (121,579)	$ (182,048)