Restructuring and Exit Costs - Restructuring Reserve (Details) - Mississippian Shale Area and Tuscaloosa Marine Shale Logistics Business - Facility Closing $ in Thousands	3 Months Ended
	Mar. 31, 2019 USD ($)
Restructuring Reserve [Roll Forward]
Balance accrued at beginning of period	$ 33
Cash payments	(13)
Balance accrued at end of period	$ 20