Guarantor Financial Statements - Cash Flow Statement (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Mar. 31, 2018	Sep. 30, 2018	Sep. 30, 2017
Condensed Financial Statements, Captions [Line Items]
Net cash provided by (used in) operating activities		$ 1,151,716	$ 638,018
Cash flows from investing activities:
Additions to oil and natural gas properties		(1,010,325)	(531,489)
Additions to midstream assets		(129,820)	(22,491)
Purchase of other property, equipment and land		(2,049)	(21,534)
Acquisition of leasehold interests		(185,658)	(1,892,864)
Acquisition of mineral interests		(335,574)	(370,855)
Acquisition of midstream assets		0	(50,279)
Proceeds from sale of assets		6,771	3,584
Funds held in escrow		(51,045)	121,391
Equity investments		(604)	(188)
Intercompany transfers		0	0
Investment in real estate	$ (109,700)	(110,654)	0
Net cash used in investing activities		(1,818,958)	(2,764,725)
Cash flows from financing activities:
Proceeds from borrowing under credit facility		1,027,500	533,000
Repayment under credit facility		(1,221,500)	(383,500)
Proceeds from senior notes		1,062,000	0
Purchase of subsidiary units by parent			0
Debt issuance costs		(14,578)	(1,714)
Public offering costs		(2,636)	(510)
Proceeds from public offerings		305,773	370,344
Contributions to subsidiaries		0
Contributions by members		0
Distributions from subsidiary		0	0
Proceeds from exercise of stock options		0	358
Proceeds from unit options exercised		140	0
Dividends to stockholders		(24,656)	0
Distributions to non-controlling interest		(68,801)	(27,640)
Intercompany transfers		0
Net cash provided by financing activities		1,063,242	490,338
Net increase (decrease) in cash and cash equivalents		396,000	(1,636,369)
Cash and cash equivalents at beginning of period	112,446	112,446	1,666,574
Cash and cash equivalents at end of period		508,446	30,205
Eliminations [Member]
Condensed Financial Statements, Captions [Line Items]
Net cash provided by (used in) operating activities		0	0
Cash flows from investing activities:
Additions to oil and natural gas properties		0	0
Additions to midstream assets		0	0
Purchase of other property, equipment and land		0	0
Acquisition of leasehold interests		0	0
Acquisition of mineral interests		0	0
Acquisition of midstream assets			0
Proceeds from sale of assets		0	0
Funds held in escrow		0	0
Equity investments		0	0
Intercompany transfers		0	0
Investment in real estate		0
Net cash used in investing activities		0	0
Cash flows from financing activities:
Proceeds from borrowing under credit facility		0	0
Repayment under credit facility		0	0
Proceeds from senior notes		0
Purchase of subsidiary units by parent			10,068
Debt issuance costs		0	0
Public offering costs		0	0
Proceeds from public offerings		0	(10,068)
Contributions to subsidiaries		(2,000)
Contributions by members		(2,000)
Distributions from subsidiary		(112,671)	(64,858)
Proceeds from exercise of stock options			0
Proceeds from unit options exercised		0
Dividends to stockholders		0
Distributions to non-controlling interest		112,671	64,858
Intercompany transfers		0
Net cash provided by financing activities		0	0
Net increase (decrease) in cash and cash equivalents		0	0
Cash and cash equivalents at beginning of period	0	0	0
Cash and cash equivalents at end of period		0	0
Parent Company [Member] | Reportable Legal Entities [Member]
Condensed Financial Statements, Captions [Line Items]
Net cash provided by (used in) operating activities		220	(25,369)
Cash flows from investing activities:
Additions to oil and natural gas properties		0	0
Additions to midstream assets		0	0
Purchase of other property, equipment and land		0	0
Acquisition of leasehold interests		0	0
Acquisition of mineral interests		0	0
Acquisition of midstream assets			0
Proceeds from sale of assets		0	0
Funds held in escrow		0	0
Equity investments		0	0
Intercompany transfers		(22,310)	(1,651,328)
Investment in real estate		0
Net cash used in investing activities		(22,310)	(1,651,328)
Cash flows from financing activities:
Proceeds from borrowing under credit facility		0	0
Repayment under credit facility		0	0
Proceeds from senior notes		1,062,000
Purchase of subsidiary units by parent			(10,068)
Debt issuance costs		(13,723)	(744)
Public offering costs		0	(77)
Proceeds from public offerings		0	0
Contributions to subsidiaries		1,000
Contributions by members		0
Distributions from subsidiary		112,671	64,858
Proceeds from exercise of stock options			358
Proceeds from unit options exercised		0
Dividends to stockholders		(24,656)
Distributions to non-controlling interest		0	0
Intercompany transfers		(696,128)
Net cash provided by financing activities		439,164	54,327
Net increase (decrease) in cash and cash equivalents		417,074	(1,622,370)
Cash and cash equivalents at beginning of period	54,074	54,074	1,643,226
Cash and cash equivalents at end of period		471,148	20,856
Guarantor Subsidiaries [Member] | Reportable Legal Entities [Member]
Condensed Financial Statements, Captions [Line Items]
Net cash provided by (used in) operating activities		975,082	569,330
Cash flows from investing activities:
Additions to oil and natural gas properties		(1,010,325)	(531,489)
Additions to midstream assets		(129,820)	(22,491)
Purchase of other property, equipment and land		2,638	(21,534)
Acquisition of leasehold interests		(185,658)	(1,892,864)
Acquisition of mineral interests		170,268	(69,722)
Acquisition of midstream assets			(50,279)
Proceeds from sale of assets		6,206	3,584
Funds held in escrow		(51,045)	121,391
Equity investments		(604)	(188)
Intercompany transfers		22,310	1,651,328
Investment in real estate		(110,654)
Net cash used in investing activities		(1,286,684)	(812,264)
Cash flows from financing activities:
Proceeds from borrowing under credit facility		470,500	312,500
Repayment under credit facility		(867,500)	(78,000)
Proceeds from senior notes		0
Purchase of subsidiary units by parent			0
Debt issuance costs		(232)	(790)
Public offering costs		0	0
Proceeds from public offerings		0	0
Contributions to subsidiaries		0
Contributions by members		0
Distributions from subsidiary		0	0
Proceeds from exercise of stock options			0
Proceeds from unit options exercised		0
Dividends to stockholders		0
Distributions to non-controlling interest		0	0
Intercompany transfers		695,128
Net cash provided by financing activities		297,896	233,710
Net increase (decrease) in cash and cash equivalents		(13,706)	(9,224)
Cash and cash equivalents at beginning of period	34,175	34,175	14,135
Cash and cash equivalents at end of period		20,469	4,911
Non-Guarantor Subsidiaries [Member] | Reportable Legal Entities [Member]
Condensed Financial Statements, Captions [Line Items]
Net cash provided by (used in) operating activities		176,414	94,057
Cash flows from investing activities:
Additions to oil and natural gas properties		0	0
Additions to midstream assets		0	0
Purchase of other property, equipment and land		(4,687)	0
Acquisition of leasehold interests		0	0
Acquisition of mineral interests		(505,842)	(301,133)
Acquisition of midstream assets			0
Proceeds from sale of assets		565	0
Funds held in escrow		0	0
Equity investments		0	0
Intercompany transfers		0	0
Investment in real estate		0
Net cash used in investing activities		(509,964)	(301,133)
Cash flows from financing activities:
Proceeds from borrowing under credit facility		557,000	220,500
Repayment under credit facility		(354,000)	(305,500)
Proceeds from senior notes		0
Purchase of subsidiary units by parent			0
Debt issuance costs		(623)	(180)
Public offering costs		(2,636)	(433)
Proceeds from public offerings		305,773	380,412
Contributions to subsidiaries		1,000
Contributions by members		2,000
Distributions from subsidiary		0	0
Proceeds from exercise of stock options			0
Proceeds from unit options exercised		140
Dividends to stockholders		0
Distributions to non-controlling interest		(181,472)	(92,498)
Intercompany transfers		1,000
Net cash provided by financing activities		326,182	202,301
Net increase (decrease) in cash and cash equivalents		(7,368)	(4,775)
Cash and cash equivalents at beginning of period	$ 24,197	24,197	9,213
Cash and cash equivalents at end of period		$ 16,829	$ 4,438