XML 66 R51.htm IDEA: XBRL DOCUMENT v3.6.0.2
Depreciation, Depletion, Amortization and Impairment Expense Related to Property and Equipment and Intangible Assets (Detail) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Property Plant And Equipment [Abstract]      
Depreciation and impairment expense $ 657,571 $ 845,543 $ 693,390
Amortization expense 3,643 3,643 3,643
Depletion expense 7,220 15,573 21,697
Total $ 668,434 $ 864,759 $ 718,730