Segment Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Sales and revenues:
Sales and revenues	$ 1,028,101	$ 1,195,579
Operating expenses:
Depletion, depreciation, and amortization	228,244	202,729
General and administrative expense	60,030	64,698
Other operating expenses	274,673	144,429
Total operating expenses	881,607	694,236
Operating income (loss)	146,494	501,343
Equity in earnings of unconsolidated affiliate	7,862	2,231
Segment assets	15,422,849	14,888,654	$ 15,261,490
Capital expenditures for segment assets	545,963	516,234
Exploration and production
Sales and revenues:
Sales and revenues	784,543	1,127,051
Gathering and compression
Sales and revenues:
Sales and revenues	4,145	2,539
Water handling and treatment
Sales and revenues:
Sales and revenues	790	65
Marketing
Sales and revenues:
Sales and revenues	238,623	65,924
Operating segments
Operating expenses:
Equity in earnings of unconsolidated affiliate	7,862	2,231
Operating segments | Exploration and production
Sales and revenues:
Sales and revenues	790,418	1,131,491
Operating expenses:
Depletion, depreciation, and amortization	195,588	174,969
General and administrative expense	46,420	51,056
Other operating expenses	77,884	53,618
Total operating expenses	735,499	643,153
Operating income (loss)	54,919	488,338
Segment assets	13,200,108	12,989,013
Capital expenditures for segment assets	472,767	457,739
Operating segments | Gathering and compression
Sales and revenues:
Sales and revenues	108,177	91,659
Operating expenses:
Depletion, depreciation, and amortization	23,638	19,924
General and administrative expense	10,362	10,138
Other operating expenses	14
Total operating expenses	45,382	38,176
Operating income (loss)	62,795	53,483
Equity in earnings of unconsolidated affiliate	7,862	2,231
Segment assets	2,217,115	1,941,668
Capital expenditures for segment assets	93,670	66,559
Operating segments | Water handling and treatment
Sales and revenues:
Sales and revenues	121,414	83,110
Operating expenses:
Depletion, depreciation, and amortization	9,018	7,836
General and administrative expense	4,093	4,319
Other operating expenses	4,910	4,344
Total operating expenses	72,893	55,121
Operating income (loss)	48,521	27,989
Segment assets	933,909	645,943
Capital expenditures for segment assets	40,285	36,954
Operating segments | Marketing
Sales and revenues:
Sales and revenues		65,924
Operating expenses:
Other operating expenses	195,739	89,993
Total operating expenses	195,739	89,993
Operating income (loss)	42,884	(24,069)
Segment assets	41,548	27,730
Elimination of intersegment transaction
Sales and revenues:
Sales and revenues	(230,531)	(176,605)
Operating expenses:
General and administrative expense	(845)	(815)
Other operating expenses	(3,874)	(3,526)
Total operating expenses	(167,906)	(132,207)
Operating income (loss)	(62,625)	(44,398)
Segment assets	(969,831)	(715,700)
Capital expenditures for segment assets	(60,759)	(45,018)
Elimination of intersegment transaction | Exploration and production
Sales and revenues:
Sales and revenues	5,875	4,440
Elimination of intersegment transaction | Gathering and compression
Sales and revenues:
Sales and revenues	104,032	89,120
Elimination of intersegment transaction | Water handling and treatment
Sales and revenues:
Sales and revenues	120,624	83,045
Elimination of intersegment transaction | Marketing
Sales and revenues:
Sales and revenues	238,623
Natural Gas, Gathering, Transportation, Marketing and Processing
Operating expenses:
Cost of goods and services sold	291,938	266,829
Natural Gas, Gathering, Transportation, Marketing and Processing | Operating segments | Exploration and production
Operating expenses:
Cost of goods and services sold	384,345	347,768
Natural Gas, Gathering, Transportation, Marketing and Processing | Operating segments | Gathering and compression
Operating expenses:
Cost of goods and services sold	11,368	8,114
Natural Gas, Gathering, Transportation, Marketing and Processing | Elimination of intersegment transaction
Operating expenses:
Cost of goods and services sold	(103,775)	(89,053)
Oil and Gas, Operation and Maintenance
Operating expenses:
Cost of goods and services sold	26,722	15,551
Oil and Gas, Operation and Maintenance | Operating segments | Exploration and production
Operating expenses:
Cost of goods and services sold	31,262	15,742
Oil and Gas, Operation and Maintenance | Operating segments | Water handling and treatment
Operating expenses:
Cost of goods and services sold	54,872	38,622
Oil and Gas, Operation and Maintenance | Elimination of intersegment transaction
Operating expenses:
Cost of goods and services sold	$ (59,412)	$ (38,813)