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Depreciation, Depletion, Amortization and Impairment Expense Related to Property and Equipment and Intangible Assets (Detail) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Property Plant And Equipment [Abstract]      
Depreciation and impairment expense $ 845,543 $ 693,390 $ 573,106
Amortization expense 3,643 3,643 3,993
Depletion expense 15,573 21,697 20,370
Total $ 864,759 $ 718,730 $ 597,469