BUSINESS COMBINATIONS BUSINESS COMBINATIONS (Details) shares in Thousands, $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2016 USD ($) a Wells shares	Dec. 31, 2017 USD ($) Wells	Dec. 31, 2016 USD ($) a Wells shares	Dec. 31, 2015 USD ($)
Business Acquisition [Line Items]
Oil and gas producing wells, gross | Wells		2,800
Issuance of common stock for acquisition of crude oil and natural gas properties		$ 0	$ 690,702	$ 0
Goodwill	$ 62,041	$ 0	62,041
Delaware Basin Acquisition [Member]
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross	$ 946,000		945,962
Payments for Deposits Applied to Debt Retirements			$ 40,000
Oil and gas producing wells, gross | Wells	30		30
Gas and Oil Area, Developed, Gross | a	57,900		57,900
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net	$ 1,637,090		$ 1,637,090
Stock Issued During Period, Shares, Acquisitions | shares	9,400
Business Combination, Pro Forma Information, Revenue of Acquiree since Acquisition Date, Actual			5,600
Business Combination, Pro Forma Information, Earnings or Loss of Acquiree since Acquisition Date, Actual			(1,700)
Issuance of common stock for acquisition of crude oil and natural gas properties			690,702
Non-Cash Basis	$ 375,000		375,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Liabilities	374,707		374,707
Delaware Basin [Member]
Business Acquisition [Line Items]
Goodwill	75,121		75,121
Goodwill, Other Increase (Decrease)			13,080
Scenario, Previously Reported [Member] | Delaware Basin [Member]
Business Acquisition [Line Items]
Goodwill	$ 62,041		$ 62,041
September 2016 Common Stock Issuance [Member]
Business Acquisition [Line Items]
Shares issued pursuant to sale of equity | shares			9,085