Asset Retirement Obligations (Tables)

6 Months Ended

Jun. 30, 2016

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,
	2016	2015
(thousands of dollars)
Balance, beginning  of period	$      4,468	$ 4,196
Liabilities settled	(49)	(178)
Accretion expense	240	450
Balance, end of period	4,659	4,468
Less:  Current portion	(121)	(121)
Less:  Liabilities held for sale	(105)	(105)
Non-current portion	$      4,433	$ 4,242