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Commitments, Contingencies and Legal Proceedings - Schedule of Reserves (Detail) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Environmental Remediation Obligations [Abstract]    
Beginning balance $ 17,105 $ 16,223
Payments (4,317) (9,118)
Accruals 40,000 10,000
Ending balance $ 52,788 $ 17,105