Income Taxes - Narrative (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Feb. 01, 2019	Dec. 31, 2017
Income Taxes Summary [Line Items]
Change in valuation allowance		$ 2,010
Net operating loss carryforwards		2,066	$ 1,971
Deferred tax assets		3,811	2,449
Deferred tax assets, valuation allowance		3,808	1,805
Deferred tax assets, valuation allowance, increase (decrease)		2,003
Income tax benefit		(19)	(331)	$ (10)
Unrecognized tax benefits		74	74	$ 79		$ 106
Uncertain tax positions that would impact effective tax rate		29
Federal
Income Taxes Summary [Line Items]
NOL carryforward		7,803
Net operating loss carryforwards		1,639
State and local
Income Taxes Summary [Line Items]
NOL carryforward		7,784
Net operating loss carryforwards		427
Unrecognized tax benefits, receivables with taxing authorities		29
Wildhorse resource development corporation
Income Taxes Summary [Line Items]
Deferred tax liabilities			$ 314		$ 314
Income tax benefit	$ 314
Deferred tax liability, plant, property and equipment and prepaid compensation	401
Deferred tax assets, operating loss carryforward, limitations		61
Wildhorse resource development corporation | Federal
Income Taxes Summary [Line Items]
Net operating loss carryforwards	$ 87
Income tax expense (benefit)
Income Taxes Summary [Line Items]
Change in valuation allowance		$ 2,010