XML 58 R46.htm IDEA: XBRL DOCUMENT v3.19.1
ASSET RETIREMENT OBLIGATION - Summary of Asset Retirement Obligation (Details) - USD ($)
$ in Thousands
3 Months Ended 12 Months Ended
Mar. 31, 2019
Mar. 31, 2018
Dec. 31, 2018
ASSET RETIREMENT OBLIGATION      
Balance, beginning of period $ 6,203 $ 5,731 $ 5,731
Liabilities settled (335)   (521)
Accretion expense 126 $ 134 993
Balance, end of period 5,994   6,203
Less: Current portion (894)   (708)
Non-current Portion $ 5,100   $ 5,495