Property, Plant and Equipment (Narrative) (Details) - USD ($)	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021	Sep. 30, 2021	Dec. 31, 2020
Property, Plant and Equipment [Line Items]
Well costs	$ 172,706,000	$ 182,401,000	$ 179,481,000		$ 181,616,000
Exploratory well costs capitalized more than one year	169,900,000
Impairment of oil and gas Properties	0	171,300,000
Proceeds from sale of oil and gas property and equipment		$ 267,700,000
Terra Nova
Property, Plant and Equipment [Line Items]
Additional percentage acquired through commercial settlement				7.525%
Vietnam
Property, Plant and Equipment [Line Items]
Exploratory well costs capitalized more than one year	94,000,000
United States
Property, Plant and Equipment [Line Items]
Exploratory well costs capitalized more than one year	47,600,000
Brunei
Property, Plant and Equipment [Line Items]
Exploratory well costs capitalized more than one year	8,200,000
MEXICO
Property, Plant and Equipment [Line Items]
Exploratory well costs capitalized more than one year	15,300,000
Canada
Property, Plant and Equipment [Line Items]
Exploratory well costs capitalized more than one year	$ 4,800,000