XML 63 R53.htm IDEA: XBRL DOCUMENT v3.5.0.2
Changes to Company's Asset Retirement Obligations (Detail) - USD ($)
$ in Thousands
9 Months Ended
Sep. 30, 2016
Sep. 30, 2015
Asset Retirement Obligation Disclosure [Abstract]    
Balance at beginning of year $ 5,692 $ 5,301
Liabilities incurred 84 322
Liabilities settled (74) (118)
Accretion expense 126 129
Revision in estimated costs of plugging oil and natural gas wells 42  
Asset retirement obligation at end of period $ 5,870 $ 5,634