Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2020

Fair Value Disclosures [Abstract]

Fair value of financial assets and liabilities measured on recurring basis

The following tables present information (in millions) about our assets and liabilities recognized at their fair values in our balance sheets categorized according to the fair value hierarchy of the inputs utilized by us to determine the fair values as of December 31, 2020 and 2019.

We have elected to offset the fair value amounts recognized for multiple similar derivative contracts executed with the same counterparty, including any related cash collateral assets or obligations as shown below; however, fair value amounts by hierarchy level are presented in the following tables on a gross basis. We have no derivative contracts that are subject to master netting arrangements that are reflected gross on the balance sheet.

	December 31, 2020
							Total Gross Fair Value		Effect of Counter- party Netting		Effect of Cash Collateral Netting		Net Carrying Value on Balance Sheet		Cash Collateral Paid or Received Not Offset
	Fair Value Hierarchy
	Level 1		Level 2		Level 3
Assets
Commodity derivative contracts	$	403	$	—	$	—	$	403	$	(373)	$	(18)	$	12	$	—
Physical purchase contracts	—		13		—		13		n/a		n/a		13		n/a
Investments of certain benefit plans	74		—		8		82		n/a		n/a		82		n/a
Total	$	477	$	13	$	8	$	498	$	(373)	$	(18)	$	107
Liabilities
Commodity derivative contracts	$	405	$	—	$	—	$	405	$	(373)	$	(32)	$	—	$	(44)
Environmental credit obligations	—		96		—		96		n/a		n/a		96		n/a
Foreign currency contracts	4		—		—		4		n/a		n/a		4		n/a
Total	$	409	$	96	$	—	$	505	$	(373)	$	(32)	$	100

	December 31, 2019
							Total Gross Fair Value		Effect of Counter- party Netting		Effect of Cash Collateral Netting		Net Carrying Value on Balance Sheet		Cash Collateral Paid or Received Not Offset
	Fair Value Hierarchy
	Level 1		Level 2		Level 3
Assets
Commodity derivative contracts	$	617	$	—	$	—	$	617	$	(612)	$	—	$	5	$	—
Foreign currency contracts	27		—		—		27		n/a		n/a		27		n/a
Investments of certain benefit plans	65		—		9		74		n/a		n/a		74		n/a
Total	$	709	$	—	$	9	$	718	$	(612)	$	—	$	106
Liabilities
Commodity derivative contracts	$	668	$	—	$	—	$	668	$	(612)	$	(56)	$	—	$	(84)
Environmental credit obligations	—		2		—		2		n/a		n/a		2		n/a
Physical purchase contracts	—		3		—		3		n/a		n/a		3		n/a
Foreign currency contracts	10		—		—		10		n/a		n/a		10		n/a
Total	$	678	$	5	$	—	$	683	$	(612)	$	(56)	$	15

Carrying amounts and estimated fair value of financial instruments

Financial instruments that we recognize in our balance sheets at their carrying amounts are shown in the following table along with their associated fair values (in millions):

		December 31, 2020				December 31, 2019
	Fair Value Hierarchy	Carrying Amount		Fair Value		Carrying Amount		Fair Value
Financial assets
Cash and cash equivalents	Level 1	$	3,313	$	3,313	$	2,583	$	2,583
Financial liabilities
Debt (excluding finance leases)	Level 2	13,013		15,103		8,881		10,583