Property, Plant And Equipment - Aging of Capitalized Exploratory Well Costs (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($) well Project	Dec. 31, 2018 USD ($) well Project	Dec. 31, 2017 USD ($) well project	Dec. 31, 2016 USD ($)
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Amount | $	$ 217,326	$ 207,855	$ 155,103	$ 101,546
No. of Wells (in wells) | well	11	9	12
No. of Projects (in projects)	5	5	6
Zero to one year
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Amount | $	$ 63,409	$ 61,096	$ 41,480
No. of Wells (in wells) | well	5	1	3
No. of Projects (in projects)	5	1	2
One to two years
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Amount | $	$ 0	$ 40,523	$ 5,812
No. of Wells (in wells) | well	0	3	1
No. of Projects (in projects)	0	2	1
Two to three years
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Amount | $	$ 27,396	$ 5,208	$ 43,200
No. of Wells (in wells) | well	1	1	2
No. of Projects (in projects)	0	1	2
Three years or more
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Amount | $	$ 126,521	$ 101,028	$ 64,611
No. of Wells (in wells) | well	5	4	6
No. of Projects (in projects)	0	1	1