SUPPLEMENTAL INFORMATION - NATURAL GAS AND CRUDE OIL PROPERTIES Costs Incurred in Natural Gas and Crude Oil Property Acquisition, Exploration and Development Activities (Unadited) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Costs Incurred, Oil and Gas Property Acquisition, Exploration, and Development Activities [Line Items]
Proved Properties	[1]	$ 172	$ 268,567	$ 3,561
Unproved Properties	[1]	18,914	1,843,985	15
Development Costs	[2]	688,165	383,336	552,104
Exploratory drilling	[3]	80,103	0	0
Geological and geophysical	[3]	3,881	4,669	0
Total Costs Incurred	[4]	$ 791,235	2,500,557	555,680
Cost Incurred to Convert PUDs to PDNP			$ 463,400	$ 204,600	$ 207,800

[1] Property acquisition costs represent costs incurred to purchase, lease, or otherwise acquire a property. Proved properties include approximately $40.9 million of infrastructure and pipeline costs in 2016.

[2] Development costs represent costs incurred to gain access to and prepare development well locations for drilling, drill and equip development wells, recomplete wells, and provide facilities to extract, treat, gather, and store crude oil, natural gas, and NGLs. Of these costs incurred for the years ended December 31, 2017, 2016, and 2015, $463.4 million, $204.6 million, and $207.8 million, respectively, were incurred to convert proved undeveloped reserves to proved developed reserves from the prior year end. These costs also include approximately $32.8 million of infrastructure and pipeline costs in 2017.

[3] Exploration costs represent costs incurred in identifying areas that may warrant examination and in examining specific areas that are considered to have prospects of containing crude oil, natural gas, and NGLs. These costs include, but are not limited to, dry hole contributions and costs of drilling and equipping exploratory wells.

[4] During the year ended 2017, we finalized our purchase price allocation for the 2016 Delaware Basin acquisition within the one year measurement period. The finalization included a reduction to our proved, undeveloped and development costs of $24.6 million. We excluded this reduction from our 2017 costs incurred as it did not relate to any cash acquisitions in 2017.