Asset Retirement Obligations (Tables)

6 Months Ended

Jun. 30, 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:

	June 30,	December 31,
	2017	2016
(thousands of dollars)
Balance, beginning  of period	$      4,894	$       4,468
Liabilities settled	(30)	(54)
Liabilities disposed	(105)
Accretion expense	263	480
Balance, end of period	5,022	4,894
Less:  Current portion	(121)	(121)
Less:  Liabilities held for sale	-	(105)
Non-current portion	$      4,901	$ 4,668