SUBSIDIARY GUARANTOR SUBSIDIARY GUARANTOR BALANCE SHEET (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 180,675	$ 244,100
Accounts receivable, net	197,598	143,392
Fair value of derivatives	14,338	8,791
Prepaid expenses and other current assets	8,613	3,542
Total current assets	401,224	399,825
Properties and equipment, net	3,933,467	4,002,994
Assets held-for-sale, net	40,084	5,272
Intercompany receivable	0	0
Investment in subsidiaries	0	0
Fair value of derivatives	0	2,386
Goodwill	0	62,041
Other assets	45,116	13,324
Total Assets	4,419,891	4,485,842
Current liabilities:
Accounts payable	150,067	66,322
Production tax liability	37,654	24,767
Fair value of derivatives	79,302	53,595
Funds held for distribution	95,811	71,339
Accrued interest payable	11,815	15,930
Other accrued expenses	42,987	38,625
Total current liabilities	417,636	270,578
Intercompany payable	0	0
Long-term debt	1,151,932	1,043,954
Deferred income taxes	191,992	400,867
Asset retirement obligations	71,006	82,612
Fair value of derivatives	22,343	27,595
Other liabilities	57,333	37,482
Total liabilities	1,912,242	1,863,088
Shareholders' Equity:
Common shares	659	657
Additional paid-in capital	2,503,294	2,489,557
Retained earnings	6,704	134,208
Treasury shares	3,008	1,668
Total stockholders' equity	2,507,649	2,622,754
Total Liabilities and Stockholders' Equity	4,419,891	4,485,842
Parent [Member]
Current assets:
Cash and cash equivalents	180,675	240,487
Accounts receivable, net	160,490	134,589
Fair value of derivatives	14,338	8,791
Prepaid expenses and other current assets	8,284	3,442
Total current assets	363,787	387,309
Properties and equipment, net	1,891,314	1,884,147
Assets held-for-sale, net	40,084	5,272
Intercompany receivable	250,279	9,415
Investment in subsidiaries	1,617,537	1,765,092
Fair value of derivatives		2,386
Goodwill		0
Other assets	42,547	13,153
Total Assets	4,205,548	4,066,774
Current liabilities:
Accounts payable	85,000	38,748
Production tax liability	35,902	24,401
Fair value of derivatives	79,302	53,595
Funds held for distribution	83,898	65,022
Accrued interest payable	11,812	15,930
Other accrued expenses	42,543	37,425
Total current liabilities	338,457	235,121
Intercompany payable	0	0
Long-term debt	1,151,932	1,043,954
Deferred income taxes	62,857	20,971
Asset retirement obligations	65,301	78,897
Fair value of derivatives	22,343	27,595
Other liabilities	57,009	37,482
Total liabilities	1,697,899	1,444,020
Shareholders' Equity:
Common shares	659	657
Additional paid-in capital	2,503,294	2,489,557
Retained earnings	6,704	(134,208)
Treasury shares	3,008	1,668
Total stockholders' equity	2,507,649	2,622,754
Total Liabilities and Stockholders' Equity	4,205,548	4,066,774
Guarantor Subsidiaries [Member]
Current assets:
Cash and cash equivalents	0	3,613
Accounts receivable, net	37,108	8,803
Fair value of derivatives	0	0
Prepaid expenses and other current assets	329	100
Total current assets	37,437	12,516
Properties and equipment, net	2,042,153	2,118,847
Assets held-for-sale, net	0	0
Intercompany receivable	0	0
Investment in subsidiaries	0	0
Fair value of derivatives		0
Goodwill		62,041
Other assets	2,569	171
Total Assets	2,082,159	2,193,575
Current liabilities:
Accounts payable	65,067	27,574
Production tax liability	1,752	366
Fair value of derivatives	0	0
Funds held for distribution	11,913	6,317
Accrued interest payable	3	0
Other accrued expenses	444	1,200
Total current liabilities	79,179	35,457
Intercompany payable	250,279	9,415
Long-term debt	0	0
Deferred income taxes	129,135	379,896
Asset retirement obligations	5,705	3,715
Fair value of derivatives	0	0
Other liabilities	324	0
Total liabilities	464,622	428,483
Shareholders' Equity:
Common shares	0	0
Additional paid-in capital	1,766,775	1,766,775
Retained earnings	(149,238)	1,683
Treasury shares	0	0
Total stockholders' equity	1,617,537	1,765,092
Total Liabilities and Stockholders' Equity	2,082,159	2,193,575
Consolidation, Eliminations [Member]
Current assets:
Cash and cash equivalents	0	0
Accounts receivable, net	0	0
Fair value of derivatives	0	0
Prepaid expenses and other current assets	0	0
Total current assets	0	0
Properties and equipment, net	0	0
Assets held-for-sale, net	0	0
Intercompany receivable	(250,279)	(9,415)
Investment in subsidiaries	(1,617,537)	(1,765,092)
Fair value of derivatives		0
Goodwill		0
Other assets	0	0
Total Assets	(1,867,816)	(1,774,507)
Current liabilities:
Accounts payable	0	0
Production tax liability	0	0
Fair value of derivatives	0	0
Funds held for distribution	0	0
Accrued interest payable	0	0
Other accrued expenses	0	0
Total current liabilities	0	0
Intercompany payable	(250,279)	(9,415)
Long-term debt	0	0
Deferred income taxes	0	0
Asset retirement obligations	0	0
Fair value of derivatives	0	0
Other liabilities	0	0
Total liabilities	(250,279)	(9,415)
Shareholders' Equity:
Common shares	0	0
Additional paid-in capital	(1,766,775)	(1,766,775)
Retained earnings	149,238	(1,683)
Treasury shares	0	0
Total stockholders' equity	(1,617,537)	(1,765,092)
Total Liabilities and Stockholders' Equity	$ (1,867,816)	$ (1,774,507)