Business Segments (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Dec. 31, 2022
Segment Reporting Information [Line Items]
Total Assets	$ 10,188,529		$ 10,308,952
External Revenues	841,716	$ 552,961
Income (Loss)	214,314	(65,486)
Continuing operations
Segment Reporting Information [Line Items]
Total Assets	10,187,800
External Revenues	841,700	553,000
Income (Loss)	214,000	(64,900)
Discontinued operations, net of tax
Segment Reporting Information [Line Items]
Total Assets	700
External Revenues	0	0
Income (Loss)	300	(600)
Corporate
Segment Reporting Information [Line Items]
Total Assets	810,700
External Revenues	0	(320,500)
Income (Loss)	(28,700)	(296,300)
Exploration and production | Operating Segments
Segment Reporting Information [Line Items]
Total Assets	9,377,100
External Revenues	841,700	873,500
Income (Loss)	242,700	231,400
Exploration and production | Operating Segments | United States
Segment Reporting Information [Line Items]
Total Assets	6,995,800
External Revenues	682,300	707,400
Income (Loss)	226,000	252,900
Exploration and production | Operating Segments | Canada
Segment Reporting Information [Line Items]
Total Assets	2,146,800
External Revenues	155,800	166,100
Income (Loss)	21,900	22,700
Exploration and production | Operating Segments | Other
Segment Reporting Information [Line Items]
Total Assets	234,500
External Revenues	3,600	0
Income (Loss)	$ (5,200)	$ (44,200)