Cash Flow Disclosures (Tables)

9 Months Ended

Sep. 30, 2016

Cash Flow Disclosures [Abstract]

Cash Flow Activities

	Nine Months Ended September 30,
(Thousands of dollars)	2016		2015
Net (increase) decrease in operating working capital other than    cash and cash equivalents:
Decrease in accounts receivable	$	75,841	389,413
Increase in inventories		(15,768)	(16,607)
Decrease (increase) in prepaid expenses		122,399	(87,051)
Decrease in deferred income tax assets		720	4,863
Decrease in accounts payable and accrued liabilities		(376,310)	(134,458)
Increase (decrease) in current income tax liabilities		40,500	(59,134)
Net (increase) decrease in noncash operating working capital	$	(152,618)	97,026
Supplementary disclosures:
Cash income taxes paid (refunded), net	$	(3,911)	111,897
Interest paid, net of amounts capitalized		52,287	60,766
Non-cash investing activities:
Asset retirement costs capitalized	$	13,959	55,258
Decrease in capital expenditure accrual		179,203	374,720