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Debt - Additional Information (Detail) - USD ($)
3 Months Ended
May 04, 2020
Nov. 11, 2019
Nov. 10, 2019
Feb. 28, 2019
Feb. 24, 2017
Feb. 24, 2016
Jul. 06, 2015
Mar. 31, 2020
Mar. 31, 2019
Dec. 31, 2018
Sep. 30, 2018
Jun. 30, 2018
Mar. 31, 2014
May 03, 2020
Sep. 19, 2019
Sep. 18, 2019
May 06, 2019
May 05, 2019
Feb. 27, 2019
Aug. 01, 2017
Feb. 23, 2017
Debt Instrument [Line Items]                                          
Debt instrument, covenant description               The indenture governing the senior unsecured notes contains covenants that, among other things, limit the ability of the Company and its restricted subsidiaries to: (i) incur additional indebtedness, (ii) pay dividends on capital stock or redeem, repurchase or retire the Company’s capital stock or subordinated indebtedness, (iii) transfer or sell assets, (iv) make investments, (v) create certain liens, (vi) enter into agreements that restrict dividends or other payments to the Company from its restricted subsidiaries, (vii) consolidate, merge or transfer all or substantially all of the assets of the Company and its restricted subsidiaries, taken as a whole, (viii) engage in transactions with affiliates, and (ix) create unrestricted subsidiaries.                          
Ratio of total funded net debt to EBITDAX   2.75% 3.00%                                    
Outstanding letters of credit               $ 29,200,000                          
BRMR and Everest Merger Sub Inc. [Member] | Minimum [Member]                                          
Debt Instrument [Line Items]                                          
Ratio of total funded net debt to EBITDAX                 4.00% 4.00% 4.00% 4.00%                  
Revolving Credit Facility [Member]                                          
Debt Instrument [Line Items]                                          
Revolving credit facility       $ 1,000,000,000                 $ 500,000,000           $ 500,000,000    
Credit facility maturity year                         2018                
Applicable margin 0.25%         0.50%                              
Borrowing base $ 475,000,000       $ 175,000,000     500,000,000           $ 500,000,000 $ 500,000,000 $ 400,000,000 $ 400,000,000 $ 375,000,000   $ 225,000,000 $ 125,000,000
Revolving credit facility, extended maturity month and year       2024-02 2020-02                                
Outstanding borrowings               150,000,000.0                          
Available capacity on the Revolving Credit Facility               $ 320,800,000                          
Reduced borrowing base (25,000,000)                                        
Prepayment requirements on cash balances $ 40,000,000                                        
Percentage of company's proved reserves and guarantees secured by mortgages               85.00%                          
Revolving Credit Facility [Member] | Minimum [Member]                                          
Debt Instrument [Line Items]                                          
Commitment fees on unused portion of revolving credit facility               0.375%                          
Revolving Credit Facility [Member] | Maximum [Member]                                          
Debt Instrument [Line Items]                                          
Commitment fees on unused portion of revolving credit facility               0.50%                          
Revolving Credit Facility [Member] | BRMR and Everest Merger Sub Inc. [Member]                                          
Debt Instrument [Line Items]                                          
Borrowing base       $ 375,000,000                                  
8.875% Senior Unsecured Notes Due 2023 [Member]                                          
Debt Instrument [Line Items]                                          
Issuance date             Jul. 06, 2015                            
Debt instrument, outstanding principal balance amount             $ 550,000,000                            
Debt instrument interest rate   8.875%         8.875% 8.875%                          
Debt instrument maturity year   2023         2023                            
Notes issued percentage price             97.903%                            
Debt instrument, proceeds             $ 525,500,000                            
8.875% Senior Unsecured Notes Due 2023 [Member] | Maximum [Member]                                          
Debt Instrument [Line Items]                                          
Debt instrument repurchase amount   $ 50,000,000                                      
8.875% Senior Unsecured Notes Due 2023 [Member] | Level 2 [Member]                                          
Debt Instrument [Line Items]                                          
Fair value of senior unsecured notes               $ 344,700,000                          
Senior PIK Notes [Member]                                          
Debt Instrument [Line Items]                                          
Debt instrument repurchase amount             $ 510,700,000