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Summary of Significant Accounting Policies - Summary of Unaudited Pro Forma Financial Information (Detail) - USD ($)
$ / shares in Units, $ in Thousands
 5 Months Ended 7 Months Ended 12 Months Ended
Dec. 31, 2018
Aug. 13, 2018
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Operating revenues $ 223,621 $ 166,630 $ 858,195 $ 768,689  
Net income (loss) $ 64,122 $ (92,754) $ (52,417) $ 96,889  
Net income per share:          
Basic income (loss) per share $ 0.61 $ (6.08) $ (0.39) $ 0.52  
Diluted $ 0.61 $ (6.08) $ (0.39) $ 0.52  
Pro Forma          
Operating revenues       $ 1,147,290 $ 1,168,585
Net income (loss)       $ 261,406 $ 180,303
Net income per share:          
Basic income (loss) per share       $ 1.00 $ 0.77
Diluted       $ 0.82 $ 0.64