Operating Leases Operating Leases (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operating Leased Assets [Line Items]
Operating Leases, Rent Expense Revenue Equipment	$ 5,000	$ 8,000	$ 1,000
Purchase Options, Land			21,600
Related Party [Member]
Operating Leased Assets [Line Items]
Operating Leases, Rent Expense Revenue Equipment			1,000
Terminal Facilities [Member]
Operating Leased Assets [Line Items]
Operating Leases, Rent Expense	4,800	3,900	2,200
Terminal Facilities [Member] | Related Party [Member]
Operating Leased Assets [Line Items]
Operating Leases, Rent Expense	$ 800	$ 1,600	$ 1,900