Annual report pursuant to Section 13 and 15(d)

Reconciliation of Asset Retirement Obligations which are Included in Other Liabilities (Detail)

v3.20.4
Reconciliation of Asset Retirement Obligations which are Included in Other Liabilities (Detail) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]    
Balance at beginning of period $ 4,934 $ 4,314
Changes in estimates 33 (2)
Liabilities incurred 121 290
Liabilities settled 0 (67)
Acquisitions of properties (16) (83)
Accretion expense 357 316
Balance at end of period $ 5,461 $ 4,934