STOCK-BASED COMPENSATION - Summary (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Options, Restricted Stock and Unit Awards
Stock compensation cost	$ 8,693	$ 11,225	$ 21,111	$ 23,217
Less amounts capitalized to oil and gas properties	(5,598)	(4,932)	(11,286)	(10,636)
Stock compensation expense	3,095	6,293	9,825	12,581
Restricted stock awards:
Options, Restricted Stock and Unit Awards
Stock compensation cost	8,056	10,646	19,857	21,972
Performance stock awards
Options, Restricted Stock and Unit Awards
Stock compensation cost	3,809	6,438	10,538	12,840
Service-based stock awards
Options, Restricted Stock and Unit Awards
Stock compensation cost	4,247	4,208	9,319	9,132
Stock option awards
Options, Restricted Stock and Unit Awards
Stock compensation cost	$ 637	$ 579	$ 1,254	$ 1,245

Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

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Amount of capitalized and expensed compensation cost from equity-based compensation arrangements.

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