Other Financial Information (Tables)

12 Months Ended

Dec. 31, 2018

Other Financial Information [Abstract]

Noncash Operating Working Capital (Increase) Decrease

(Thousands of dollars)	2018		2017	2016
Accounts receivable	$	(89,070)	114,401	119,671
Inventories		12,216	26,883	(5,171)
Prepaid expenses		(17,341)	29,570	149,946
Deferred income tax assets		–	–	-
Accounts payable and accrued liabilities		(51,769)	(51,439)	(328,078)
Current income tax liabilities		(23,844)	16,999	24,943
Net (increase) decrease in noncash operating working capital	$	(169,808)	136,414	(38,689)
Supplementary disclosures (including discontinued operations):
Cash income taxes paid, net of refunds	$	129,296	68,076	6,707
Interest paid, net of amounts capitalized of $5,258 in 2018,  $4,488 in 2017 and $4,322 in 2016		167,750	147,975	127,798
Noncash investing activities, related to continuing operations:
Asset retirement costs capitalized	$	353,436	8,509	13,690
Decrease (increase) in capital expenditure accrual		(42,467)	99,199	158,885