Operating Leases (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Operating Leased Assets [Line Items]
Operating Leases, Rent Expense	$ 0	$ 1,700	$ 300	$ 3,600
Terminal Facilities
Operating Leased Assets [Line Items]
Operating Leases, Rent Expense	600	1,200	1,400	2,600
Terminal Facilities | Related Party
Operating Leased Assets [Line Items]
Operating Leases, Rent Expense	0	214	0	461
Related Party Transaction, Expenses from Transactions with Related Party	$ 0	$ 200	$ 0	$ 500