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Depreciation, Depletion, Amortization and Impairment Expense Related to Property and Equipment and Intangible Assets and Liabilities (Detail) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Property Plant And Equipment [Abstract]      
Depreciation and impairment expense $ 753,510 $ 657,571 $ 845,543
Amortization expense 21,764 3,643 3,643
Depletion expense 8,067 7,220 15,573
Total $ 783,341 $ 668,434 $ 864,759