VARIABLE INTEREST ENTITIES - Cavalier Minerals (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Mar. 31, 2016	Oct. 06, 2015	Nov. 10, 2014
All Dale I | Cavalier Minerals
Variable Interest Entities
Noncontrolling ownership interest (as a percent)	71.70%
All Dale I | Funding Commitments | Cavalier Minerals
Variable Interest Entities
Funding commitment				$ 49,000
All Dale II | Cavalier Minerals
Variable Interest Entities
Noncontrolling ownership interest (as a percent)	72.80%
All Dale II | Funding Commitments | Cavalier Minerals
Variable Interest Entities
Funding commitment			$ 100,000
Cavalier Minerals | Funding Commitments | Alliance Minerals
Variable Interest Entities
Funding commitment	$ 888	$ 61,023
Cavalier Minerals | Funding Commitments | Bluegrass Minerals
Variable Interest Entities
Funding commitment	$ 37	$ 2,542
Cavalier Minerals | Initial Funding Commitment | Alliance Minerals
Variable Interest Entities
Funding commitment				48,000
Cavalier Minerals | Initial Funding Commitment | Bluegrass Minerals
Variable Interest Entities
Funding commitment				$ 2,000
Cavalier Minerals | Additional Funding Commitment | Alliance Minerals
Variable Interest Entities
Funding commitment			96,000
Cavalier Minerals | Additional Funding Commitment | Bluegrass Minerals
Variable Interest Entities
Funding commitment			$ 4,000