Supplemental Condensed Consolidated Financial Information (Condensed Consolidating Statements of Cash Flows (Unaudited)) (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
OPERATING ACTIVITIES:
Net cash provided by (used in) operating activities	$ 236,535	$ 184,792
INVESTING ACTIVITIES:
Capital expenditures	(304,054)	(167,392)
Producing properties and other acquisitions	(769)	(55,429)
Proceeds from disposition of assets	25,316	20,137
Other	0	(1,500)
Net cash provided by (used in) investing activities	(279,507)	(204,184)
FINANCING ACTIVITIES:
Borrowings under credit agreement	71,200	251,401
Payments under credit agreement	(249,200)	(250,100)
Intercompany borrowings (advances), net	0	0
Payments on capitalized leases	(2,869)	(2,967)
Proceeds from investments of non-controlling interests	300,000	0
Contributions from Unit	0	0
Transaction costs associated with non-controlling interests	(2,303)	0
Proceeds from issuance of common stock, net of issuance costs	0	18,623
Book overdrafts	17,000	2,364
Net cash provided by (used in) financing activities	133,828	19,321
Net increase (decrease) in cash and cash equivalents	90,856	(71)
Cash and cash equivalents, beginning of period	701	893
Cash and cash equivalents, end of period	91,557	822
Consolidating Adjustments [Member]
OPERATING ACTIVITIES:
Net cash provided by (used in) operating activities	128,605	0
INVESTING ACTIVITIES:
Capital expenditures	0	0
Producing properties and other acquisitions	0	0
Proceeds from disposition of assets	0	0
Other	0	0
Net cash provided by (used in) investing activities	0	0
FINANCING ACTIVITIES:
Borrowings under credit agreement	0	0
Payments under credit agreement	0	0
Intercompany borrowings (advances), net	(128,080)	0
Payments on capitalized leases	0	0
Proceeds from investments of non-controlling interests	0	0
Contributions from Unit	(525)	0
Transaction costs associated with non-controlling interests	0	0
Proceeds from issuance of common stock, net of issuance costs	0	0
Book overdrafts	0	0
Net cash provided by (used in) financing activities	(128,605)	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	(103,436)	822
INVESTING ACTIVITIES:
Capital expenditures	22	(3,595)
Producing properties and other acquisitions	0	0
Proceeds from disposition of assets	30	955
Other	0	0
Net cash provided by (used in) investing activities	52	(2,640)
FINANCING ACTIVITIES:
Borrowings under credit agreement	69,200	251,401
Payments under credit agreement	(247,200)	(250,100)
Intercompany borrowings (advances), net	248,343	(20,483)
Payments on capitalized leases	0	0
Proceeds from investments of non-controlling interests	102,958	0
Contributions from Unit	0	0
Transaction costs associated with non-controlling interests	(2,303)	0
Proceeds from issuance of common stock, net of issuance costs	0	18,623
Book overdrafts	14,143	2,364
Net cash provided by (used in) financing activities	185,141	1,805
Net increase (decrease) in cash and cash equivalents	81,757	(13)
Cash and cash equivalents, beginning of period	510	517
Cash and cash equivalents, end of period	82,267	504
Combined Guarantor Subsidiaries [Member]
OPERATING ACTIVITIES:
Net cash provided by (used in) operating activities	215,350	149,963
INVESTING ACTIVITIES:
Capital expenditures	(275,434)	(152,055)
Producing properties and other acquisitions	(769)	(55,429)
Proceeds from disposition of assets	25,199	19,124
Other	0	(1,500)
Net cash provided by (used in) investing activities	(251,004)	(189,860)
FINANCING ACTIVITIES:
Borrowings under credit agreement	0	0
Payments under credit agreement	0	0
Intercompany borrowings (advances), net	35,714	39,839
Payments on capitalized leases	0	0
Proceeds from investments of non-controlling interests	0	0
Contributions from Unit	0	0
Transaction costs associated with non-controlling interests	0	0
Proceeds from issuance of common stock, net of issuance costs	0	0
Book overdrafts	0	0
Net cash provided by (used in) financing activities	35,714	39,839
Net increase (decrease) in cash and cash equivalents	60	(58)
Cash and cash equivalents, beginning of period	191	376
Cash and cash equivalents, end of period	251	318
Combined Non-Guarantor Subsidiaries [Member]
OPERATING ACTIVITIES:
Net cash provided by (used in) operating activities	(3,984)	34,007
INVESTING ACTIVITIES:
Capital expenditures	(28,642)	(11,742)
Producing properties and other acquisitions	0	0
Proceeds from disposition of assets	87	58
Other	0	0
Net cash provided by (used in) investing activities	(28,555)	(11,684)
FINANCING ACTIVITIES:
Borrowings under credit agreement	2,000	0
Payments under credit agreement	(2,000)	0
Intercompany borrowings (advances), net	(155,977)	(19,356)
Payments on capitalized leases	(2,869)	(2,967)
Proceeds from investments of non-controlling interests	197,042	0
Contributions from Unit	525	0
Transaction costs associated with non-controlling interests	0	0
Proceeds from issuance of common stock, net of issuance costs	0	0
Book overdrafts	2,857	0
Net cash provided by (used in) financing activities	41,578	(22,323)
Net increase (decrease) in cash and cash equivalents	9,039	0
Cash and cash equivalents, beginning of period	0	0
Cash and cash equivalents, end of period	$ 9,039	$ 0