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ACCRUED FINAL CAPPING, CLOSURE AND POST CLOSURE - Summary of Changes to Accrued Capping, Closure and Post-Closure Liabilities (Detail) - USD ($)
$ in Thousands
9 Months Ended
Sep. 30, 2018
Sep. 30, 2017
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]    
Beginning balance $ 62,290 $ 44,207
Obligations incurred 2,874 2,187
Revision in estimates 1,492 9,598
Accretion expense 4,175 3,164
Obligations settled (2,310) (586)
Ending balance $ 68,521 $ 58,570