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Asset Retirement Obligations - Information Related to Asset Retirement Obligations (Detail)
$ in Thousands
9 Months Ended
Sep. 30, 2020
USD ($)
Asset Retirement Obligation Disclosure [Abstract]  
Beginning Balance $ 226,137
Additions to asset retirement obligations 477
Accretion expense 3,091
Liabilities settled (5,766)
Ending Balance $ 223,939