Supplemental Condensed Consolidated Financial Information (Condensed Consolidating Statements of Cash Flows (Unaudited)) (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
OPERATING ACTIVITIES:
Net cash provided by (used in) operating activities	$ 154,693	$ 117,055
INVESTING ACTIVITIES:
Capital expenditures	(189,916)	(107,933)
Producing properties and other acquisitions	(962)	(52,956)
Proceeds from disposition of assets	23,528	19,556
Other	0	(1,500)
Net cash used in investing activities	(167,350)	(142,833)
FINANCING ACTIVITIES:
Borrowings under credit agreement	71,200	160,600
Payments under credit agreement	(249,200)	(156,500)
Intercompany borrowings (advances), net	0	0
Payments on capitalized leases	(1,901)	(1,901)
Proceeds from investments of non-controlling interests	300,000	0
Transaction costs associated with non-controlling interests	(2,254)	0
Proceeds from issuance of common stock, net of issuance costs	0	18,623
Book overdrafts	(1,581)	4,912
Net cash provided in financing activities	116,264	25,734
Net increase (decrease) in cash and cash equivalents	103,607	(44)
Cash and cash equivalents, beginning of period	701	893
Cash and cash equivalents, end of period	104,308	849
Consolidating Adjustments [Member]
OPERATING ACTIVITIES:
Net cash provided by (used in) operating activities	126,993	0
INVESTING ACTIVITIES:
Capital expenditures	0	0
Producing properties and other acquisitions	0	0
Proceeds from disposition of assets	0	0
Other		0
Net cash used in investing activities	0	0
FINANCING ACTIVITIES:
Borrowings under credit agreement	0	0
Payments under credit agreement	0	0
Intercompany borrowings (advances), net	(126,993)	0
Payments on capitalized leases	0	0
Proceeds from investments of non-controlling interests	0
Transaction costs associated with non-controlling interests	0
Proceeds from issuance of common stock, net of issuance costs		0
Book overdrafts	0	0
Net cash provided in financing activities	(126,993)	0
Net increase (decrease) in cash and cash equivalents	0	0
Cash and cash equivalents, beginning of period	0	0
Cash and cash equivalents, end of period	0	0
Parent [Member]
OPERATING ACTIVITIES:
Net cash provided by (used in) operating activities	(102,500)	(13,497)
INVESTING ACTIVITIES:
Capital expenditures	(13)	(3,380)
Producing properties and other acquisitions	0	0
Proceeds from disposition of assets	30	955
Other		0
Net cash used in investing activities	17	(2,425)
FINANCING ACTIVITIES:
Borrowings under credit agreement	71,200	160,600
Payments under credit agreement	(249,200)	(156,500)
Intercompany borrowings (advances), net	277,902	(11,708)
Payments on capitalized leases	0	0
Proceeds from investments of non-controlling interests	102,958
Transaction costs associated with non-controlling interests	(2,254)
Proceeds from issuance of common stock, net of issuance costs		18,623
Book overdrafts	(1,581)	4,912
Net cash provided in financing activities	199,025	15,927
Net increase (decrease) in cash and cash equivalents	96,542	5
Cash and cash equivalents, beginning of period	510	517
Cash and cash equivalents, end of period	97,052	522
Combined Guarantor Subsidiaries [Member]
OPERATING ACTIVITIES:
Net cash provided by (used in) operating activities	145,000	106,718
INVESTING ACTIVITIES:
Capital expenditures	(173,097)	(97,337)
Producing properties and other acquisitions	(962)	(52,956)
Proceeds from disposition of assets	23,427	18,557
Other		(1,500)
Net cash used in investing activities	(150,632)	(133,236)
FINANCING ACTIVITIES:
Borrowings under credit agreement	0	0
Payments under credit agreement	0	0
Intercompany borrowings (advances), net	5,695	26,469
Payments on capitalized leases	0	0
Proceeds from investments of non-controlling interests	0
Transaction costs associated with non-controlling interests	0
Proceeds from issuance of common stock, net of issuance costs		0
Book overdrafts	0	0
Net cash provided in financing activities	5,695	26,469
Net increase (decrease) in cash and cash equivalents	63	(49)
Cash and cash equivalents, beginning of period	191	376
Cash and cash equivalents, end of period	254	327
Combined Non-Guarantor Subsidiaries [Member]
OPERATING ACTIVITIES:
Net cash provided by (used in) operating activities	(14,800)	23,834
INVESTING ACTIVITIES:
Capital expenditures	(16,806)	(7,216)
Producing properties and other acquisitions	0	0
Proceeds from disposition of assets	71	44
Other		0
Net cash used in investing activities	(16,735)	(7,172)
FINANCING ACTIVITIES:
Borrowings under credit agreement	0	0
Payments under credit agreement	0	0
Intercompany borrowings (advances), net	(156,604)	(14,761)
Payments on capitalized leases	(1,901)	(1,901)
Proceeds from investments of non-controlling interests	197,042
Transaction costs associated with non-controlling interests	0
Proceeds from issuance of common stock, net of issuance costs		0
Book overdrafts	0	0
Net cash provided in financing activities	38,537	(16,662)
Net increase (decrease) in cash and cash equivalents	7,002	0
Cash and cash equivalents, beginning of period	0	0
Cash and cash equivalents, end of period	$ 7,002	$ 0