Acquisitions - Narrative (Details) $ in Thousands | May 31, 2019USD ($)shares | Mar. 29, 2019USD ($)shares | Mar. 14, 2019USD ($) | Feb. 05, 2019USD ($)shares | Sep. 28, 2018USD ($) | Aug. 31, 2018USD ($)shares | Jul. 31, 2018USD ($)trancheshares | Mar. 01, 2018USD ($) | Jun. 30, 2019USD ($) | Mar. 31, 2019 | Jun. 30, 2018USD ($) | Dec. 31, 2018shares | Jun. 30, 2019USD ($) | Jun. 30, 2018USD ($) | Mar. 31, 2019USD ($) | Jun. 30, 2019shares |
Business Acquisition [Line Items] | | | | | | | | | | | | | | | | |
Cash consideration | $ | | | | | | | | | | | | | $ 91,903 | $ 150,139 | | |
Transaction costs incurred | $ | | | | | | | | | $ 85 | | $ 0 | | $ 438 | $ 0 | | |
Highlander Oil & Gas Holdings LLC (Highlander) | MGY Louisiana LLC | | | | | | | | | | | | | | | | |
Business Acquisition [Line Items] | | | | | | | | | | | | | | | | |
Percent of units held | | | | 85.00% | | | | | | 85.00% | | | | | | |
Karnes County Assets | | | | | | | | | | | | | | | | |
Business Acquisition [Line Items] | | | | | | | | | | | | | | | | |
Cash payments to acquire certain oil and natural gas properties, subject to customary closing adjustments | $ | $ 36,300 | | | | | | | | | | | | | | | |
Highlander Acquisition | Highlander Oil & Gas Holdings LLC (Highlander) | | | | | | | | | | | | | | | | |
Business Acquisition [Line Items] | | | | | | | | | | | | | | | | |
Total consideration | $ | | | | $ 51,900 | | | | | | | | | | | | |
Eocene-Tuscaloosa Zone, Ultra Deep Structure Gas Well | Highlander Oil & Gas Holdings LLC (Highlander) | | | | | | | | | | | | | | | | |
Business Acquisition [Line Items] | | | | | | | | | | | | | | | | |
Percent working interest acquired | | | | 72.00% | | | | | | | | | | | | |
Gulf Coast Ultra Deep Royalty Trust | Highlander Oil & Gas Holdings LLC (Highlander) | | | | | | | | | | | | | | | | |
Business Acquisition [Line Items] | | | | | | | | | | | | | | | | |
Number of units acquired | | | | 31,100,000 | | | | | | | | | | | | |
Class A Common Stock | Karnes County Assets | | | | | | | | | | | | | | | | |
Business Acquisition [Line Items] | | | | | | | | | | | | | | | | |
Shares issued as consideration to acquire certain oil and natural gas properties (in shares) | 3,100,000 | | | | | | | | | | | | | | | |
EnerVest Business Combination | | | | | | | | | | | | | | | | |
Business Acquisition [Line Items] | | | | | | | | | | | | | | | | |
Cash consideration | $ | | | | | | | $ 1,214,966 | | | | | | | | | |
Transaction costs incurred | $ | | | | | | | | | | | | | | | $ 24,800 | |
Debt issuance costs incurred in connection with consummation of Business Combination | $ | | | | | | | | | | | | | | | $ 23,500 | |
Total purchase price consideration | $ | | | | | | | $ 2,782,204 | | | | | | | | | |
EnerVest Business Combination | Non-Compete Agreement | Tranche One | | | | | | | | | | | | | | | | |
Business Acquisition [Line Items] | | | | | | | | | | | | | | | | |
Estimated economic life of intangible asset | | | | | | | 2 years 6 months | | | | | | | | | |
EnerVest Business Combination | Non-Compete Agreement | Tranche Two | | | | | | | | | | | | | | | | |
Business Acquisition [Line Items] | | | | | | | | | | | | | | | | |
Estimated economic life of intangible asset | | | | | | | 4 years | | | | | | | | | |
EnerVest Business Combination | Class A Common Stock | | | | | | | | | | | | | | | | |
Business Acquisition [Line Items] | | | | | | | | | | | | | | | | |
Equity interests issued in business combination (in shares) | | | | | | | 31,800,000 | | | | | | | | | |
EnerVest Business Combination | Class A Common Stock | Affiliate | | | | | | | | | | | | | | | | |
Business Acquisition [Line Items] | | | | | | | | | | | | | | | | |
Number of shares authorized for issuance based on achievement of certain stock price thresholds (in shares) | | | | | | | 4,000,000 | | | | | | | | | |
Number of tranches | tranche | | | | | | | 2 | | | | | | | | | |
EnerVest Business Combination | Class A Common Stock | Affiliate | Tranche One | | | | | | | | | | | | | | | | |
Business Acquisition [Line Items] | | | | | | | | | | | | | | | | |
Number of shares authorized for issuance based on achievement of certain stock price thresholds (in shares) | | | | | | | 2,000,000 | | | | | | | | | |
EnerVest Business Combination | Class A Common Stock | Affiliate | Tranche Two | | | | | | | | | | | | | | | | |
Business Acquisition [Line Items] | | | | | | | | | | | | | | | | |
Number of shares authorized for issuance based on achievement of certain stock price thresholds (in shares) | | | | | | | 2,000,000 | | | | | | | | | |
EnerVest Business Combination | Class B Common Stock | | | | | | | | | | | | | | | | |
Business Acquisition [Line Items] | | | | | | | | | | | | | | | | |
Equity interests issued in business combination (in shares) | | | | | | | 83,900,000 | | | | | | | | | |
EnerVest Business Combination | Magnolia LLC Units | | | | | | | | | | | | | | | | |
Business Acquisition [Line Items] | | | | | | | | | | | | | | | | |
Equity interests issued in business combination (in shares) | | | | | | | 83,900,000 | | | | | | | | | |
EnerVest Business Combination | Karnes County Contributors | | | | | | | | | | | | | | | | |
Business Acquisition [Line Items] | | | | | | | | | | | | | | | | |
Cash consideration | $ | | | | | | | $ 911,500 | | | | | | | | | |
Net cash payment from final settlement | $ | | $ 4,300 | | | | | | | | | | | | | | |
Shares forfeited pursuant to Contribution and Merger Agreement (in shares) | | 2,100,000 | | | | | | | | | | | | | | |
EnerVest Business Combination | Karnes County Contributors | Karnes County Contribution Agreement | Affiliate | | | | | | | | | | | | | | | | |
Business Acquisition [Line Items] | | | | | | | | | | | | | | | | |
Equity interests issued in business combination (in shares) | | | | | | | 13,000,000 | | | | | | | | | |
Term of contribution agreement | | | | | | | 5 years | | | | | | | | | |
EnerVest Business Combination | Karnes County Contributors | Class A Common Stock | | | | | | | | | | | | | | | | |
Business Acquisition [Line Items] | | | | | | | | | | | | | | | | |
Equity interests issued in business combination (in shares) | | | | | | | 31,800,000 | | | | | | | | | |
Shares forfeited pursuant to Contribution and Merger Agreement (in shares) | | 500,000 | | | | | | | | | | | | | | |
EnerVest Business Combination | Karnes County Contributors | Class A Common Stock | Karnes County Contribution Agreement | Affiliate | | | | | | | | | | | | | | | | |
Business Acquisition [Line Items] | | | | | | | | | | | | | | | | |
Additional shares issued upon meeting stock price thresholds (in shares) | | | | | | | | | | | | 3,600,000 | | | | 3,600,000 |
EnerVest Business Combination | Karnes County Contributors | Class B Common Stock | | | | | | | | | | | | | | | | |
Business Acquisition [Line Items] | | | | | | | | | | | | | | | | |
Equity interests issued in business combination (in shares) | | | | | | | 83,900,000 | | | | | | | | | |
Shares forfeited pursuant to Contribution and Merger Agreement (in shares) | | 1,600,000 | | | | | | | | | | | | | | |
EnerVest Business Combination | Karnes County Contributors | Class B Common Stock | Karnes County Contribution Agreement | Affiliate | | | | | | | | | | | | | | | | |
Business Acquisition [Line Items] | | | | | | | | | | | | | | | | |
Additional shares issued upon meeting stock price thresholds (in shares) | | | | | | | | | | | | 9,400,000 | | | | 9,400,000 |
EnerVest Business Combination | Karnes County Contributors | Magnolia LLC Units | | | | | | | | | | | | | | | | |
Business Acquisition [Line Items] | | | | | | | | | | | | | | | | |
Equity interests issued in business combination (in shares) | | | | | | | 83,900,000 | | | | | | | | | |
Shares forfeited pursuant to Contribution and Merger Agreement (in shares) | | 1,600,000 | | | | | | | | | | | | | | |
EnerVest Business Combination | Karnes County Contributors | Exchange of Class B Common Stock and Magnolia LLC Units for Class A Common Stock | Class B Common Stock together with Magnolia LLC Units | | | | | | | | | | | | | | | | |
Business Acquisition [Line Items] | | | | | | | | | | | | | | | | |
Exchange ratio for equity interests issued | | | | | | | 1 | | | | | | | | | |
EnerVest Business Combination | Giddings Sellers | | | | | | | | | | | | | | | | |
Business Acquisition [Line Items] | | | | | | | | | | | | | | | | |
Cash consideration | $ | | | | | | | $ 282,700 | | | | | | | | | |
EnerVest Business Combination | Giddings Sellers | Giddings Purchase Agreement | Affiliate | | | | | | | | | | | | | | | | |
Business Acquisition [Line Items] | | | | | | | | | | | | | | | | |
Authorized amount of cash earnount payments | $ | | | | | | | 47,000 | | | | | | | | | |
Cash payment to fully settle earnout obligation | $ | | | | | $ 26,000 | | | | | | | | | | | |
EnerVest Business Combination | Ironwood Sellers | | | | | | | | | | | | | | | | |
Business Acquisition [Line Items] | | | | | | | | | | | | | | | | |
Cash consideration | $ | | | | | | | $ 25,000 | | | | | | | | | |
Harvest | | | | | | | | | | | | | | | | |
Business Acquisition [Line Items] | | | | | | | | | | | | | | | | |
Cash consideration | $ | | | | | | $ 133,300 | | | | | | | | | | |
Total purchase price consideration | $ | | | | | | $ 191,500 | | | | | | | | | | |
Harvest | Class A Common Stock | | | | | | | | | | | | | | | | |
Business Acquisition [Line Items] | | | | | | | | | | | | | | | | |
Equity interests issued in business combination (in shares) | | | | | | 4,200,000 | | | | | | | | | | |
Harvest | Harvest | | | | | | | | | | | | | | | | |
Business Acquisition [Line Items] | | | | | | | | | | | | | | | | |
Net cash payment from final settlement | $ | | | $ 1,400 | | | | | | | | | | | | | |
GulfTex Acquisition | | | | | | | | | | | | | | | | |
Business Acquisition [Line Items] | | | | | | | | | | | | | | | | |
Total purchase price consideration | $ | | | | | | | | $ 150,100 | | | | | | | | |