Leases (Summary of Amounts Recognized in Condensed Consolidated Balance Sheet) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Assets
Operating lease assets	$ 56,031	$ 76,401
Finance lease assets	25,921	23,723
Total leased assets	97,776	117,589
Liabilities
Current operating leases	19,575	25,700
Non-current operating leases	37,177	51,091
Total operating lease liabilities	56,752	76,791
Current finance leases	2,914	17,636
Non-current finance leases	36,394	21,501
Total finance lease liabilities	39,308	39,137
Total lease liabilities	$ 96,060	$ 115,928
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	us-gaap:OtherLiabilitiesCurrent	us-gaap:OtherLiabilitiesCurrent
Rail
Assets
Finance lease assets	$ 15,824	$ 17,465