Other Financial Information (Tables)

12 Months Ended

Dec. 31, 2017

Other Financial Information [Abstract]

Schedule of Noncash Operating Working Capital (Increase) Decrease

(Thousands of dollars)	2017		2016	2015
Accounts receivable	$	114,401	119,671	297,625
Inventories		26,883	(5,171)	(15,340)
Prepaid expenses		29,570	149,946	(144,845)
Deferred income tax assets		–	–	3,924
Accounts payable and accrued liabilities		(51,439)	(328,078)	(36,887)
Current income tax liabilities		16,999	24,943	(69,413)
Net (increase) decrease in noncash operating working capital	$	136,414	(38,689)	35,064
Supplementary disclosures (including discontinued operations):
Cash income taxes paid, net of refunds	$	68,076	6,707	118,667
Interest paid, net of amounts capitalized of $4,488 in 2017,  $4,322 in 2016 and $7,290 in 2015		147,975	127,798	110,386
Noncash investing activities, related to continuing operations:
Asset retirement costs capitalized	$	8,509	13,690	76,775
Decrease in capital expenditure accrual		99,199	158,885	462,474