Segment Reporting - Identifiable Assets by Industry Segment (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Segment Reconciliation [Abstract]
Total assets	$ 261,334	$ 330,842
Operating Segments
Segment Reconciliation [Abstract]
Total assets	261,334	330,842
Operating Segments | Marketing
Segment Reconciliation [Abstract]
Total assets	105,885	141,402
Operating Segments | Transportation
Segment Reconciliation [Abstract]
Total assets	62,990	58,483
Cash and other
Segment Reconciliation [Abstract]
Total assets	$ 92,459	$ 130,957