DECOMMISSIONING LIABILITIES (Tables)

12 Months Ended

Dec. 31, 2017

Other Provisions, Contingent Liabilities And Contingent Assets [Abstract]

Disclosure of decommissioning liabilities

($000s)	2017			2016
Balance, beginning of year	$	62,844		$	96,423
Incurred on development activities	1,501			911
Acquired through business combinations	—			552
Revisions on estimates	3,210			(2,292		)
Decommissioning costs incurred	(2,758		)	(2,927		)
Reversed on dispositions	(5,473		)	(31,536		)
Accretion expense	1,287			1,713
Balance, end of year	$	60,611		$	62,844