Income Taxes - Components of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Operating Loss Carryforwards [Line Items]
Net deferred tax liabilities	$ 1,687,862	$ 108,048
Net operating loss and other carryforwards	154,408	74,997
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Liabilities Noncurrent	1,402,834
Deferred Tax Assets, Valuation Allowance, Noncurrent	(13,900)
Deferred Tax Assets, Tax Credit Carryforwards, Alternative Minimum Tax	75,700
Noncurrent deferred tax assets
Net operating loss and other carryforwards	154,408	74,997
Derivative instruments	0	22,918
Stock based compensation	7,021	942
The Partnership's investment in the Operating Company	94,468	0
Other	8,634	2,464
Deferred tax assets	264,531	101,321
Valuation allowance	(13,932)	(104)
Deferred tax assets, net of valuation allowance	250,599	101,217
Noncurrent deferred tax liabilities
Oil and natural gas properties and equipment	1,825,237	202,997
Amount of deferred tax liability attributable to taxable temporary differences from midstream assets	66,728	6,268
Deferred Tax Liabilities, Other	46,496	0
Total noncurrent deferred tax liabilities	1,938,461	$ 209,265
Energen [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss and other carryforwards	13,500
Deferred Tax Assets, Valuation Allowance, Noncurrent	(13,600)
Deferred Tax Assets, Tax Credit Carryforwards, Alternative Minimum Tax	38,200
Noncurrent deferred tax assets
Net operating loss and other carryforwards	$ 13,500