Other Financial Information - Noncash Opearting Working Capital (Increase) Decrease (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018		Dec. 31, 2017
Other Financial Information [Abstract]
(Increase) decrease in accounts receivable	$ (232,037)	$ (30,212)		$ (15,462)
(Increase) decrease in inventories	10,258	16,794		15,429
(Increase) decrease in prepaid expenses	4,650	(10,011)		15,752
Increase (decrease) in accounts payable and accrued liabilities	196,773	8,784		70,376
Increase (decrease) in income taxes payable	3,469	(1,458)		(7,249)
Net (increase) decrease in noncash operating working capital	(16,887)	(16,103)	[1]	78,846	[1]
Cash income taxes paid, net of refunds	(6,645)	(7,603)		(5,969)
Interest paid, net of amounts capitalized of $1.8 million in 2019 and $0.2 million in 2018	179,722	158,071		144,455
Asset retirement costs capitalized	33,874	346,387		126
(Increase) decrease in capital expenditure accrual	(73,426)	9,817		$ 16,325
Interest paid, net of amounts capitalized	$ 1,800	$ 200

[1] Reclassified to conform with current presentation (see Note E)