Impairment (Details)	3 Months Ended			9 Months Ended
	Sep. 30, 2020 USD ($) $ / bbl	Jun. 30, 2020 USD ($) $ / bbl	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($) $ / bbl	Sep. 30, 2019 USD ($)	Sep. 30, 2020 $ / Mcf	Jun. 30, 2020 $ / Mcf
Assets and Liabilities Held for Sale [Line Items]
Impairment	$ 44,043,000		$ 165,507,000	$ 253,797,000	$ 165,507,000
Full cost ceiling limitation impairment	$ 44,000,000.0		0	$ 215,800,000	0
Commodity price (usd per unit)	43.40	47.17		43.40		1.97	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		$ 38,000,000.0	$ 0	$ 38,000,000.0	$ 0