Asset Retirement Obligations (Tables)

3 Months Ended

Mar. 31, 2017

Asset Retirement Obligation Disclosure [Abstract]

Summary of Asset Retirement Obligation

The following table summarizes the changes in the reserve for future restoration and reclamation costs on the balance sheet:

	March 31,	December 31,
	2017	2016
(thousands of dollars)
Balance, beginning  of period	$      4,894	$       4,468
Liabilities settled	(14)	(54)
Liabilities disposed	(105)
Accretion expense	132	480
Balance, end of period	4,907	4,894
Less:  Current portion	(121)	(121)
Less:  Liabilities held for sale	-	(105)
Non-current portion	$      4,786	$ 4,668