Other Financial Information (Tables)

12 Months Ended

Dec. 31, 2015

Other Financial Information [Abstract]

Noncash Operating Working Capital (Increase) Decrease

(Thousands of dollars)	2015		2014	2013
Accounts receivable	$	297,625	175,820	224,281
Inventories		(15,340)	25,697	14,166
Prepaid expenses		(144,845)	6,575	195,013
Deferred income tax assets		3,924	6,884	15,510
Accounts payable and accrued liabilities		(36,887)	(54,785)	(176,543)
Current income tax liabilities		(69,413)	(163,920)	(6,098)
Net (increase) decrease in noncash              operating working capital	$	35,064	(3,729)	266,329
Supplementary disclosures (including discontinued operations):
Cash income taxes paid, net of refunds	$	118,667	573,799	457,006
Interest paid, net of amounts capitalized		110,386	114,232	60,501
Non-cash investing activities, related to continuing operations:
Asset retirement costs capitalized	$	76,775	70,568	172,488
Decrease (increase) in capital expenditure accrual		462,474	93,080	(197,054)