Other Financial Information (Tables)

12 Months Ended

Dec. 31, 2014

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Noncash Operating Working Capital (Increased) Decreased

(Thousands of dollars)	2014		2013	2012
Accounts receivable	$	175,820	224,281	(382,137)
Inventories		25,697	14,166	(94,907)
Prepaid expenses		6,575	195,013	(245,881)
Deferred income tax assets		6,884	15,510	(7,218)
Accounts payable and accrued liabilities		(54,785)	(176,543)	534,353
Current income tax liabilities		(163,920)	(6,098)	27,610
Net (increase) decrease in noncash              operating working capital	$	(3,729)	266,329	(168,180)