Derivatives - Fair Value (Details) - USD ($) $ in Millions	May 05, 2020	Mar. 31, 2020	Dec. 31, 2019
Marketing Derivatives
Gross and net fair values of outstanding derivatives (in millions)
Collateral deposited with clearinghouses and brokers		$ 212
Initial margin			$ 65
Interest Rate Swaps
Gross and net fair values of outstanding derivatives (in millions)
Collateral paid netted against derivative liabilities		204	104
Interest Rate Swaps | Subsequent Event
Gross and net fair values of outstanding derivatives (in millions)
Collateral paid netted against derivative liabilities	$ 225
Other current assets | Oil Collars and Calls
Gross and net fair values of outstanding derivatives (in millions)
Netting, asset		0	0
Total net fair value, asset		834	92
Other current assets | Marketing Derivatives
Gross and net fair values of outstanding derivatives (in millions)
Netting, asset		(6,445)	(973)
Total net fair value, asset		385	51
Other current assets | Interest Rate Swaps
Gross and net fair values of outstanding derivatives (in millions)
Netting, asset		0	0
Total net fair value, asset		1	5
Long-term receivables and other assets, net | Marketing Derivatives
Gross and net fair values of outstanding derivatives (in millions)
Netting, asset		(91)	(4)
Total net fair value, asset		19	12
Long-term receivables and other assets, net | Interest Rate Swaps
Gross and net fair values of outstanding derivatives (in millions)
Netting, asset		0	0
Total net fair value, asset		1	5
Accrued liabilities | Marketing Derivatives
Gross and net fair values of outstanding derivatives (in millions)
Netting and collateral, liability		(6,445)	(973)
Total net fair value, liability		(92)	(79)
Accrued liabilities | Interest Rate Swaps
Gross and net fair values of outstanding derivatives (in millions)
Netting and collateral, liability		0	0
Total net fair value, liability		(90)	(657)
Deferred credits and other liabilities - other | Oil Collars and Calls
Gross and net fair values of outstanding derivatives (in millions)
Netting and collateral, liability		0	0
Total net fair value, liability		(58)	(160)
Deferred credits and other liabilities - other | Marketing Derivatives
Gross and net fair values of outstanding derivatives (in millions)
Netting and collateral, liability		(91)	(4)
Total net fair value, liability		(1)	(1)
Deferred credits and other liabilities - other | Interest Rate Swaps
Gross and net fair values of outstanding derivatives (in millions)
Netting and collateral, liability		0	0
Total net fair value, liability		(1,954)	(776)
Deferred credits and other liabilities - other | Warrants
Gross and net fair values of outstanding derivatives (in millions)
Netting and collateral, liability		0	0
Total net fair value, liability		(23)	(107)
Level 1 | Other current assets | Oil Collars and Calls
Gross and net fair values of outstanding derivatives (in millions)
Commodity contract derivative asset, gross		0	0
Level 1 | Other current assets | Marketing Derivatives
Gross and net fair values of outstanding derivatives (in millions)
Commodity contract derivative asset, gross		6,438	945
Level 1 | Other current assets | Interest Rate Swaps
Gross and net fair values of outstanding derivatives (in millions)
Commodity contract derivative asset, gross		0	0
Level 1 | Long-term receivables and other assets, net | Marketing Derivatives
Gross and net fair values of outstanding derivatives (in millions)
Commodity contract derivative asset, gross		91	4
Level 1 | Long-term receivables and other assets, net | Interest Rate Swaps
Gross and net fair values of outstanding derivatives (in millions)
Commodity contract derivative asset, gross		0	0
Level 1 | Accrued liabilities | Marketing Derivatives
Gross and net fair values of outstanding derivatives (in millions)
Commodity contract derivative liability, gross		(6,170)	(1,008)
Level 1 | Accrued liabilities | Interest Rate Swaps
Gross and net fair values of outstanding derivatives (in millions)
Commodity contract derivative liability, gross		0	0
Level 1 | Deferred credits and other liabilities - other | Oil Collars and Calls
Gross and net fair values of outstanding derivatives (in millions)
Commodity contract derivative liability, gross		0	0
Level 1 | Deferred credits and other liabilities - other | Marketing Derivatives
Gross and net fair values of outstanding derivatives (in millions)
Commodity contract derivative liability, gross		(91)	(4)
Level 1 | Deferred credits and other liabilities - other | Interest Rate Swaps
Gross and net fair values of outstanding derivatives (in millions)
Commodity contract derivative liability, gross		0	0
Level 1 | Deferred credits and other liabilities - other | Warrants
Gross and net fair values of outstanding derivatives (in millions)
Commodity contract derivative liability, gross		0	0
Level 2 | Other current assets | Oil Collars and Calls
Gross and net fair values of outstanding derivatives (in millions)
Commodity contract derivative asset, gross		834	92
Level 2 | Other current assets | Marketing Derivatives
Gross and net fair values of outstanding derivatives (in millions)
Commodity contract derivative asset, gross		392	79
Level 2 | Other current assets | Interest Rate Swaps
Gross and net fair values of outstanding derivatives (in millions)
Commodity contract derivative asset, gross		1	5
Level 2 | Long-term receivables and other assets, net | Marketing Derivatives
Gross and net fair values of outstanding derivatives (in millions)
Commodity contract derivative asset, gross		19	12
Level 2 | Long-term receivables and other assets, net | Interest Rate Swaps
Gross and net fair values of outstanding derivatives (in millions)
Commodity contract derivative asset, gross		1	5
Level 2 | Accrued liabilities | Marketing Derivatives
Gross and net fair values of outstanding derivatives (in millions)
Commodity contract derivative liability, gross		(367)	(44)
Level 2 | Accrued liabilities | Interest Rate Swaps
Gross and net fair values of outstanding derivatives (in millions)
Commodity contract derivative liability, gross		(90)	(657)
Level 2 | Deferred credits and other liabilities - other | Oil Collars and Calls
Gross and net fair values of outstanding derivatives (in millions)
Commodity contract derivative liability, gross		(58)	(160)
Level 2 | Deferred credits and other liabilities - other | Marketing Derivatives
Gross and net fair values of outstanding derivatives (in millions)
Commodity contract derivative liability, gross		(1)	(1)
Level 2 | Deferred credits and other liabilities - other | Interest Rate Swaps
Gross and net fair values of outstanding derivatives (in millions)
Commodity contract derivative liability, gross		(1,954)	(776)
Level 2 | Deferred credits and other liabilities - other | Warrants
Gross and net fair values of outstanding derivatives (in millions)
Commodity contract derivative liability, gross		(23)	(107)
Level 3 | Other current assets | Oil Collars and Calls
Gross and net fair values of outstanding derivatives (in millions)
Commodity contract derivative asset, gross		0	0
Level 3 | Other current assets | Marketing Derivatives
Gross and net fair values of outstanding derivatives (in millions)
Commodity contract derivative asset, gross		0	0
Level 3 | Other current assets | Interest Rate Swaps
Gross and net fair values of outstanding derivatives (in millions)
Commodity contract derivative asset, gross		0	0
Level 3 | Long-term receivables and other assets, net | Marketing Derivatives
Gross and net fair values of outstanding derivatives (in millions)
Commodity contract derivative asset, gross		0	0
Level 3 | Long-term receivables and other assets, net | Interest Rate Swaps
Gross and net fair values of outstanding derivatives (in millions)
Commodity contract derivative asset, gross		0	0
Level 3 | Accrued liabilities | Marketing Derivatives
Gross and net fair values of outstanding derivatives (in millions)
Commodity contract derivative liability, gross		0	0
Level 3 | Accrued liabilities | Interest Rate Swaps
Gross and net fair values of outstanding derivatives (in millions)
Commodity contract derivative liability, gross		0	0
Level 3 | Deferred credits and other liabilities - other | Oil Collars and Calls
Gross and net fair values of outstanding derivatives (in millions)
Commodity contract derivative liability, gross		0	0
Level 3 | Deferred credits and other liabilities - other | Marketing Derivatives
Gross and net fair values of outstanding derivatives (in millions)
Commodity contract derivative liability, gross		0	0
Level 3 | Deferred credits and other liabilities - other | Interest Rate Swaps
Gross and net fair values of outstanding derivatives (in millions)
Commodity contract derivative liability, gross		0	0
Level 3 | Deferred credits and other liabilities - other | Warrants
Gross and net fair values of outstanding derivatives (in millions)
Commodity contract derivative liability, gross		$ 0	$ 0