Business Segments (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Segment Reporting Information [Line Items]
Total Assets	$ 9,716,419		$ 9,716,419		$ 9,766,697
External Revenues	758,331	$ 959,645	2,357,514	$ 2,615,949
Income (Loss)	151,112	277,804	422,032	583,974
Continuing operations
Segment Reporting Information [Line Items]
Total Assets	9,715,500		9,715,500
External Revenues	758,300	959,600	2,357,500	2,615,900
Income (Loss)	151,700	278,200	424,100	584,700
Discontinued operations, net of tax
Segment Reporting Information [Line Items]
Total Assets	900		900
External Revenues	0	0	0	0
Income (Loss)	(600)	(400)	(2,100)	(700)
Corporate
Segment Reporting Information [Line Items]
Total Assets	317,600		317,600
External Revenues	4,200	3,200	4,200	3,300
Income (Loss)	(33,700)	(30,100)	(88,900)	(105,400)
Exploration and Production | Operating Segments
Segment Reporting Information [Line Items]
Total Assets	9,397,900		9,397,900
External Revenues	754,100	956,400	2,353,300	2,612,600
Income (Loss)	185,400	308,300	513,000	690,100
Exploration and Production | Operating Segments | United States
Segment Reporting Information [Line Items]
Total Assets	7,088,300		7,088,300
External Revenues	597,000	823,700	1,936,100	2,202,200
Income (Loss)	138,800	310,300	459,000	705,200
Exploration and Production | Operating Segments | Canada
Segment Reporting Information [Line Items]
Total Assets	2,043,000		2,043,000
External Revenues	157,900	129,300	413,800	403,300
Income (Loss)	24,200	10,500	52,500	34,900
Exploration and Production | Operating Segments | Other
Segment Reporting Information [Line Items]
Total Assets	266,600		266,600
External Revenues	(800)	3,400	3,400	7,100
Income (Loss)	$ 22,400	$ (12,500)	$ 1,500	$ (50,000)