Business Segments (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023
Segment Reporting Information [Line Items]
Total Assets	$ 9,893,718		$ 9,893,718		$ 9,766,697
External Revenues	802,771	$ 814,588	1,599,183	$ 1,656,304
Income (Loss)	156,262	91,855	270,920	306,169
Minimum
Segment Reporting Information [Line Items]
Income (Loss)	156,200
Continuing operations
Segment Reporting Information [Line Items]
Total Assets	9,892,600		9,892,600
External Revenues	802,800	814,600	1,599,200	1,656,300
Income (Loss)	156,800	92,500	272,400	306,500
Discontinued operations, net of tax
Segment Reporting Information [Line Items]
Total Assets	1,100		1,100
External Revenues	0	0	0	0
Income (Loss)	(600)	(600)	(1,500)	(300)
Corporate
Segment Reporting Information [Line Items]
Total Assets	375,300		375,300
External Revenues	0	100	0	100
Income (Loss)	(27,700)	(46,600)	(55,200)	(75,200)
Exploration and Production | Operating Segments
Segment Reporting Information [Line Items]
Total Assets	9,517,300		9,517,300
External Revenues	802,800	814,500	1,599,200	1,656,200
Income (Loss)	184,500	139,100	327,600	381,700
Exploration and Production | Operating Segments | United States
Segment Reporting Information [Line Items]
Total Assets	7,222,600		7,222,600
External Revenues	679,500	696,200	1,339,100	1,378,500
Income (Loss)	185,700	168,900	320,200	394,900
Exploration and Production | Operating Segments | Canada
Segment Reporting Information [Line Items]
Total Assets	2,050,500		2,050,500
External Revenues	119,000	118,300	255,900	274,100
Income (Loss)	8,900	2,500	28,300	24,400
Exploration and Production | Operating Segments | Other
Segment Reporting Information [Line Items]
Total Assets	244,200		244,200
External Revenues	4,300	0	4,200	3,600
Income (Loss)	$ (10,100)	$ (32,300)	$ (20,900)	$ (37,600)