Business Segments (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022	Dec. 31, 2022
Segment Reporting Information [Line Items]
Total Assets	$ 10,249,530		$ 10,249,530		$ 10,308,952
External Revenues	814,588	$ 1,101,057	1,656,304	$ 1,654,018
Income (Loss)	91,855	409,504	306,169	344,018
Continuing operations
Segment Reporting Information [Line Items]
Total Assets	10,248,400		10,248,400
External Revenues	814,600	1,101,100	1,656,300	1,654,000
Income (Loss)	92,500	410,400	306,500	345,500
Discontinued operations, net of tax
Segment Reporting Information [Line Items]
Total Assets	1,200		1,200
External Revenues	0	0	0	0
Income (Loss)	(600)	(900)	(300)	(1,500)
Corporate
Segment Reporting Information [Line Items]
Total Assets	822,800		822,800
External Revenues	100	(97,200)	100	(417,800)
Income (Loss)	(46,600)	(124,800)	(75,200)	(421,100)
Exploration and production | Operating Segments
Segment Reporting Information [Line Items]
Total Assets	9,425,600		9,425,600
External Revenues	814,500	1,198,300	1,656,200	2,071,800
Income (Loss)	139,100	535,200	381,700	766,600
Exploration and production | Operating Segments | United States
Segment Reporting Information [Line Items]
Total Assets	6,963,300		6,963,300
External Revenues	696,200	978,000	1,378,500	1,685,400
Income (Loss)	168,900	491,500	394,900	744,400
Exploration and production | Operating Segments | Canada
Segment Reporting Information [Line Items]
Total Assets	2,234,700		2,234,700
External Revenues	118,300	206,600	274,100	372,700
Income (Loss)	2,500	47,200	24,400	69,900
Exploration and production | Operating Segments | Other
Segment Reporting Information [Line Items]
Total Assets	227,600		227,600
External Revenues	0	13,700	3,600	13,700
Income (Loss)	$ (32,300)	$ (3,500)	$ (37,600)	$ (47,700)