Property, Plant And Equipment - Aging of Capitalized Exploratory Well Costs (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2020 USD ($) project well	Dec. 31, 2019 USD ($) well project	Dec. 31, 2018 USD ($) project well	Dec. 31, 2017 USD ($)
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Amount | $	$ 181,616	$ 217,326	$ 207,855	$ 155,103
No. of Wells (in wells) | well	11	11	9
No. of Projects (in projects) | project	5	5	5
Zero to one year
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Amount | $	$ 0	$ 63,409	$ 61,096
No. of Wells (in wells) | well	0	5	1
No. of Projects (in projects) | project	0	5	1
One to two years
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Amount | $	$ 54,220	$ 0	$ 40,523
No. of Wells (in wells) | well	5	0	3
No. of Projects (in projects) | project	5	0	2
Two to three years
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Amount | $	$ 0	$ 27,396	$ 5,208
No. of Wells (in wells) | well	0	1	1
No. of Projects (in projects) | project	0	0	1
Three years or more
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Amount | $	$ 127,396	$ 126,521	$ 101,028
No. of Wells (in wells) | well	6	5	4
No. of Projects (in projects) | project	0	0	1