Investments - Investment Income (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Schedule of Equity Method Investments
Total Investment Loss (Income)	$ 2,730	$ 1,748	$ 8,139	$ (593)
White Cliffs
Schedule of Equity Method Investments
Total Investment Loss (Income)	(549)	(841)	(1,264)	(1,889)
Advantage
Schedule of Equity Method Investments
Total Investment Loss (Income)	(1,311)	(1,513)	(3,387)	(3,754)
Delaware Crossing
Schedule of Equity Method Investments
Total Investment Loss (Income)	752	355	1,472	1,538
EPIC Y-Grade
Schedule of Equity Method Investments
Total Investment Loss (Income)	7,977	1,024	13,595	1,054
EPIC Crude
Schedule of Equity Method Investments
Total Investment Loss (Income)	1,972	3,245	8,873	3,245
EPIC Propane
Schedule of Equity Method Investments
Total Investment Loss (Income)	36	0	61	0
Saddlehorn
Schedule of Equity Method Investments
Total Investment Loss (Income)	(5,712)	0	(10,338)	0
Other
Schedule of Equity Method Investments
Total Investment Loss (Income)	$ (435)	$ (522)	$ (873)	$ (787)