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Subsequent Event - Additional Information (Detail) - USD ($)
$ in Millions
3 Months Ended 12 Months Ended
Mar. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Subsequent Event [Line Items]        
Exploration expense for well costs   $ 233 $ 362 $ 507
Kosmos Energy Ltd | Oldfield-1 Exploration Well in Gulf of Mexico        
Subsequent Event [Line Items]        
Exploration expense for well costs   $ 15    
Scenario Forecast | Kosmos Energy Ltd | Oldfield-1 Exploration Well in Gulf of Mexico        
Subsequent Event [Line Items]        
Exploration expense for well costs $ 15