Impairments of Property, Equipment, Goodwill and Intangible Assets (Narrative) (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2020 USD ($) segment	Dec. 31, 2019 USD ($)
Property and equipment, net	$ 5,415,989	$ 5,516,347
Intangible assets, net	$ 1,120,197	$ 1,163,063
Number of geographic operating segments | segment	5
Exploration and Production [Member]
Property and equipment, net	$ 832,739
Intangible assets, net	59,600
Exploration and Production [Member] | Williston Basin [Member]
Property and equipment, net	376,122
Intangible assets, net	$ 2,430
Exploration and Production [Member] | Williston Basin [Member] | Minimum [Member]
Estimated write down if operations impaired	90.00%
Exploration and Production [Member] | Williston Basin [Member] | Maximum [Member]
Estimated write down if operations impaired	95.00%