Impairment (Details)	3 Months Ended	6 Months Ended
Jun. 30, 2020 USD ($) $ / bbl	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($) $ / bbl	Jun. 30, 2019 USD ($)	Jun. 30, 2020 $ / Mcf
Assets and Liabilities Held for Sale [Line Items]
Impairment	$ 201,784,000	$ 0	$ 209,754,000	$ 0
Full cost ceiling limitation impairment		163,800,000	$ 171,800,000
Commodity price (usd per unit)	47.17		47.17		2.07
Disposal Group, Held-for-sale, Not Discontinued Operations \| Corporate Headquarters Building
Assets and Liabilities Held for Sale [Line Items]
Impairment of Real Estate	$ 0	$ 38,000,000.0	$ 0	$ 38,000,000.0

Amount of write-down of assets recognized in the income statement. Includes, but is not limited to, losses from tangible assets, intangible assets and goodwill.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3602-108585

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 45
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=109226348&loc=d3e2420-110228

Name:	us-gaap_AssetImpairmentCharges
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration