Other Financial Information (Noncash Operating Working Capital (Increase) Decrease) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Mar. 31, 2021	Sep. 30, 2021	Sep. 30, 2020
Net (increase) decrease in operating working capital, excluding cash and cash equivalents:
Decrease in accounts receivable			$ 75,100	$ 251,706
Decrease in inventories			9,718	4,747
(Increase) in prepaid expenses			(6,682)	(17,400)
Increase (decrease) in accounts payable and accrued liabilities			40,687	(264,078)
(Decrease) in income taxes payable			(1,493)	(1,236)
Net (increase) decrease in noncash operating working capital			117,330	(26,261)
Supplementary disclosures:
Cash income taxes paid, net of refunds			1,685	(12,559)
Interest paid, net of amounts capitalized of $11.6 million in 2021 and $5.9 million in 2020			127,793	139,651
Capitalized interest paid			11,600	5,900
Non-cash investing activities:
Asset retirement costs capitalized			36,300	6,342
Decrease in capital expenditure accrual			$ 31,301	$ 74,742
Impairment of asset retirement obligation		$ 74,400
Other operating income	$ 71,800
Asset life extension period			10 years