OPERATIONS, SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES AND RECENTLY ADOPTED AND RECENTLY ISSUED ACCOUNTING STANDARDS - Recently Adopted Accounting Standards (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Dec. 31, 2018	Dec. 31, 2018	Jul. 01, 2018	Jun. 30, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accumulated (losses) earnings	$ (86,238)	$ (86,238)		$ (89,898)
Change in fair value of equity securities	(3,631)	(5,099)
Carrying value of equity securities	$ 17,700	$ 17,700		$ 19,200
Contango
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Investment shares owned (in shares)	809,744	809,744
Rubicon
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Investment shares owned (in shares)	3,597,823	3,597,823
ASU 2016-01
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accumulated (losses) earnings			$ 1,200