Other Financial Information (Noncash Operating Working Capital (Increase) Decrease) (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Other Financial Information [Abstract]
Asset retirement obligations	$ 37,300
Net (increase) decrease in operating working capital, excluding cash and cash equivalents:
(Increase) decrease in accounts receivable	(128,698)	$ (32,372)
(Increase) decrease in inventories	4,398	21,367
(Increase) decrease in prepaid expenses	(3,745)	(3)
Increase (decrease) in accounts payable and accrued liabilities	165,224	1,185
Increase (decrease) in income taxes payable	3,078	322
Net (increase) decrease in noncash operating working capital	40,257	(9,501)	[1]
Supplementary disclosures:
Cash income taxes paid, net of refunds	(4,563)	(4,508)
Interest paid, net of amounts capitalized of $0.2 million in 2019 and $0 in 2018	137,116	113,820
Amounts capitalized	0
Non-cash investing activities:
Asset retirement costs capitalized	48,203	2,907
(Increase) decrease in capital expenditure accrual	$ (52,659)	$ 27,551

[1] Reclassified to conform to current presentation (See Note A).