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FINAL CAPPING, CLOSURE AND POST-CLOSURE COSTS (Detail) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]    
Beginning balance $ 44,207 $ 41,041
Obligations incurred 3,022 2,441
Revisions in estimates 11,498 (2,052)
Accretion expense 4,401 3,606
Obligations settled (838) (829)
Ending balance $ 62,290 $ 44,207