Derivative Instruments and Hedging Activities Quantitative Disclosures Related to Derivative Instruments (Details) - Not Designated as Hedging Instrument bbl in Thousands, MMBTU in Millions		9 Months Ended	12 Months Ended
		Sep. 30, 2020 MMBTU bbl	Dec. 31, 2019 MMBTU bbl
Natural Gas, Financial fixed futures/swaps | Purchases
Derivative [Line Items]
Derivative, gross notional volume (TBtu) | MMBTU	[1]	4	10
Natural Gas, Financial fixed futures/swaps | Sales
Derivative [Line Items]
Derivative, gross notional volume (TBtu) | MMBTU	[1]	25	19
Natural gas, Financial basis futures/swaps | Purchases
Derivative [Line Items]
Derivative, gross notional volume (TBtu) | MMBTU	[1]	3	11
Natural gas, Financial basis futures/swaps | Sales
Derivative [Line Items]
Derivative, gross notional volume (TBtu) | MMBTU	[1]	32	30
Natural gas, Financial swaptions | Purchases
Derivative [Line Items]
Derivative, gross notional volume (TBtu) | MMBTU	[1],[2]	0	0
Natural gas, Financial swaptions | Sales
Derivative [Line Items]
Derivative, gross notional volume (TBtu) | MMBTU	[1],[2]	8	2
Physical purchases/sales | Purchases
Derivative [Line Items]
Derivative, gross notional volume (TBtu) | MMBTU	[1]	0	0
Physical purchases/sales | Sales
Derivative [Line Items]
Derivative, gross notional volume (TBtu) | MMBTU	[1]	1	6
Crude oil, Financial Futures/swaps | Purchases
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Volume | bbl	[3]	0	0
Crude oil, Financial Futures/swaps | Sales
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Volume | bbl	[3]	540	990
Crude oil, Financial options | Purchases
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Volume | bbl	[2],[3]	0	0
Crude oil, Financial options | Sales
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Volume | bbl	[2],[3]	90	225
Natural gas liquids, Financial Futures/swaps | Purchases
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Volume | bbl	[4]	1,395	2,490
Natural gas liquids, Financial Futures/swaps | Sales
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Volume | bbl	[4]	1,410	2,415
Natural gas liquids, Options [Member] | Purchases
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Volume | bbl	[4]	0	0
Natural gas liquids, Options [Member] | Sales
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Volume | bbl	[4]	75	0
Natural gas
Derivative [Line Items]
Percent of contract with durations of one year or less		91.90%	86.60%
Percent of contracts with durations of more than one year and less than two years		8.10%	13.40%
Crude oil (for condensate)
Derivative [Line Items]
Percent of contract with durations of one year or less		92.90%	72.80%
Percent of contracts with durations of more than one year and less than two years		7.10%	27.20%
Natural gas liquids
Derivative [Line Items]
Percent of contract with durations of one year or less		97.30%	72.20%
Percent of contracts with durations of more than one year and less than two years		2.70%	27.80%

[1] As of September 30, 2020, 91.9% of the natural gas contracts had durations of one year or less and 8.1% had durations of more than one year and less than two years. As of December 31, 2019, 86.6% of the natural gas contracts had durations of one year or less and 13.4% had durations of more than one year and less than two years.

[2] The notional volume contains a combined derivative instrument consisting of a fixed price swap and a sold option, which gives the counterparties the right, but not the obligation, to increase the notional volume hedged under the fixed price swap until the option expiration date. The notional volume represents the volume prior to option exercise.

[3] As of September 30, 2020, 92.9% of the crude oil (for condensate) contracts had durations of one year or less and 7.1% had durations of more than one year and less than two years. As of December 31, 2019, 72.8% of the crude oil (for condensate) contracts had durations of one year or less and 27.2% had durations of more than one year and less than two years.

[4] As of September 30, 2020, 97.3% of the natural gas liquids contracts had durations of one year or less and 2.7% had durations of more than one year and less than two years. As of December 31, 2019, 72.2% of the natural gas liquids contracts had durations of one year or less and 27.8% had durations of more than one year and less than two years.