Segment Information (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Sales and revenues:
Sales and revenues	$ 1,045,649	$ 1,076,532	$ 989,344	$ 1,028,101	$ 1,021,726	$ 647,880	$ 790,389	$ 1,195,579	$ 4,139,626	$ 3,655,574	$ 1,744,525
Operating expenses:
Impairment of unproved properties									549,437	159,598	162,935
Impairment of gathering systems and facilities									9,658	23,431	0
Depletion, depreciation, and amortization									972,465	824,610	809,873
General and administrative expense									240,344	251,196	239,324
Total operating expenses	1,092,279	1,071,728	1,022,107	881,607	834,667	719,932	666,646	694,236	4,067,721	2,915,481	2,720,326
Operating income (loss)	(46,630)	$ 4,804	$ (32,763)	$ 146,494	187,059	$ (72,052)	$ 123,743	$ 501,343	71,905	740,093	(975,801)
Equity in earnings of unconsolidated affiliates									40,280	20,194	485
Segment assets	15,519,464				15,261,490				15,519,464	15,261,490
Exploration and production
Sales and revenues:
Sales and revenues									3,565,300	3,406,203	1,334,656
Gathering and compression
Sales and revenues:
Sales and revenues									17,817	11,386	16,028
Water handling and treatment
Sales and revenues:
Sales and revenues									3,527	1,334	792
Marketing
Sales and revenues:
Sales and revenues									552,982	236,651	393,049
Operating segments
Sales and revenues:
Sales and revenues									4,139,626	3,655,574	1,744,525
Operating expenses:
Impairment of unproved properties									549,437
Impairment of gathering systems and facilities									9,658
Depletion, depreciation, and amortization									972,465	824,610	809,873
General and administrative expense									240,344	251,196	239,324
Other operating expenses									820,306	654,979	738,201
Total operating expenses									4,067,721	2,915,481	2,720,326
Operating income (loss)									71,905	740,093	(975,801)
Equity in earnings of unconsolidated affiliates									40,280	20,194	485
Segment assets	15,519,464				15,261,490				15,519,464	15,261,490	14,255,550
Capital expenditures for segment assets									2,210,586	2,216,753	2,495,429
Operating segments | Exploration and production
Sales and revenues:
Sales and revenues									3,477,828	3,423,561	1,352,980
Operating expenses:
Impairment of unproved properties									549,437
Depletion, depreciation, and amortization									841,645	704,152	709,127
General and administrative expense									181,305	195,153	186,672
Other operating expenses									129,947	261,578	241,755
Total operating expenses									3,637,466	2,695,770	2,334,426
Operating income (loss)									(159,638)	727,791	(981,446)
Segment assets	12,986,945				13,074,027				12,986,945	13,074,027	12,512,973
Capital expenditures for segment assets									1,923,488	1,859,481	2,220,688
Operating segments | Gathering and compression
Sales and revenues:
Sales and revenues									521,149	396,466	307,944
Operating expenses:
Impairment of gathering systems and facilities									9,658
Depletion, depreciation, and amortization									84,057	87,268	70,847
General and administrative expense									46,609	40,337	39,832
Other operating expenses									258	23,535	(809)
Total operating expenses									189,580	190,287	137,968
Operating income (loss)									331,569	206,179	169,976
Equity in earnings of unconsolidated affiliates									40,280	20,194	485
Segment assets	2,465,858				2,253,163				2,465,858	2,253,163	1,750,354
Capital expenditures for segment assets									444,413	346,217	231,044
Operating segments | Water handling and treatment
Sales and revenues:
Sales and revenues									507,373	376,031	282,267
Operating expenses:
Depletion, depreciation, and amortization									46,763	33,190	29,899
General and administrative expense									15,020	18,475	14,331
Other operating expenses									(88,973)	17,061	14,401
Total operating expenses									236,066	258,428	195,017
Operating income (loss)									271,307	117,603	87,250
Segment assets	1,077,004				804,296				1,077,004	804,296	615,687
Capital expenditures for segment assets									97,699	194,502	188,188
Operating segments | Marketing
Sales and revenues:
Sales and revenues									552,982	236,651	393,049
Operating expenses:
Other operating expenses									686,055	366,281	499,343
Total operating expenses									686,055	366,281	499,343
Operating income (loss)									(133,073)	(129,630)	(106,294)
Segment assets	34,499				36,701				34,499	36,701	37,890
Elimination of intersegment transaction
Sales and revenues:
Sales and revenues									(919,706)	(777,135)	(591,715)
Operating expenses:
General and administrative expense									(2,590)	(2,769)	(1,511)
Other operating expenses									93,019	(13,476)	(16,489)
Total operating expenses									(681,446)	(595,285)	(446,428)
Operating income (loss)									(238,260)	(181,850)	(145,287)
Segment assets	$ (1,044,842)				$ (906,697)				(1,044,842)	(906,697)	(661,354)
Capital expenditures for segment assets									(255,014)	(183,447)	(144,491)
Elimination of intersegment transaction | Exploration and production
Sales and revenues:
Sales and revenues									(87,472)	17,358	18,324
Elimination of intersegment transaction | Gathering and compression
Sales and revenues:
Sales and revenues									503,332	385,080	291,916
Elimination of intersegment transaction | Water handling and treatment
Sales and revenues:
Sales and revenues									503,846	374,697	281,475
Gathering, compression, water handling and treatment
Operating expenses:
Cost of goods and services sold									1,339,358	1,095,639	882,838
Gathering, compression, water handling and treatment | Operating segments
Operating expenses:
Cost of goods and services sold									1,339,358	1,095,639	882,838
Gathering, compression, water handling and treatment | Operating segments | Exploration and production
Operating expenses:
Cost of goods and services sold									1,792,898	1,441,129	1,146,221
Gathering, compression, water handling and treatment | Operating segments | Gathering and compression
Operating expenses:
Cost of goods and services sold									48,998	39,147	28,098
Gathering, compression, water handling and treatment | Operating segments | Water handling and treatment
Operating expenses:
Cost of goods and services sold									552
Gathering, compression, water handling and treatment | Elimination of intersegment transaction
Operating expenses:
Cost of goods and services sold									(503,090)	(384,637)	(291,481)
Oil and Gas, Operation and Maintenance
Operating expenses:
Cost of goods and services sold									136,153	89,057	50,090
Oil and Gas, Operation and Maintenance | Operating segments
Operating expenses:
Cost of goods and services sold									136,153	89,057	50,090
Oil and Gas, Operation and Maintenance | Operating segments | Exploration and production
Operating expenses:
Cost of goods and services sold									142,234	93,758	50,651
Oil and Gas, Operation and Maintenance | Operating segments | Water handling and treatment
Operating expenses:
Cost of goods and services sold									262,704	189,702	136,386
Oil and Gas, Operation and Maintenance | Elimination of intersegment transaction
Operating expenses:
Cost of goods and services sold									$ (268,785)	$ (194,403)	$ (136,947)