Derivative Instruments and Hedging Activities - Balance Sheet Location (Details) - USD ($) $ in Millions		Jun. 30, 2020	Dec. 31, 2019
Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset Including Not Subject to Master Netting Arrangement	[1]	$ 38	$ 49
Derivative Liability, Fair Value, Gross Liability Including Not Subject to Master Netting Arrangement	[1]	29	38
Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset Including Not Subject to Master Netting Arrangement	[2]	0	0
Derivative Liability, Fair Value, Gross Liability Including Not Subject to Master Netting Arrangement	[2]	9	3
Interest rate swaps | Designated as Hedging Instrument | Other Current Assets
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset Including Not Subject to Master Netting Arrangement		0	0
Interest rate swaps | Designated as Hedging Instrument | Other Current Liabilities
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability Including Not Subject to Master Netting Arrangement		6	1
Interest rate swaps | Designated as Hedging Instrument | Other Noncurrent Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset Including Not Subject to Master Netting Arrangement		0	0
Interest rate swaps | Designated as Hedging Instrument | Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability Including Not Subject to Master Netting Arrangement		3	2
Natural gas | Financial futures/swaps | Not Designated as Hedging Instrument | Other Current Assets
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset Including Not Subject to Master Netting Arrangement		7	7
Natural gas | Financial futures/swaps | Not Designated as Hedging Instrument | Other Current Liabilities
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability Including Not Subject to Master Netting Arrangement		7	5
Natural gas | Financial futures/swaps | Not Designated as Hedging Instrument | Other Noncurrent Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset Including Not Subject to Master Netting Arrangement		0	0
Natural gas | Financial futures/swaps | Not Designated as Hedging Instrument | Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability Including Not Subject to Master Netting Arrangement		0	1
Natural gas | Financial swaptions | Not Designated as Hedging Instrument | Other Current Assets
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset Including Not Subject to Master Netting Arrangement		1	0
Natural gas | Financial swaptions | Not Designated as Hedging Instrument | Other Current Liabilities
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability Including Not Subject to Master Netting Arrangement		2	0
Natural gas | Financial swaptions | Not Designated as Hedging Instrument | Other Noncurrent Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset Including Not Subject to Master Netting Arrangement		1	0
Natural gas | Financial swaptions | Not Designated as Hedging Instrument | Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability Including Not Subject to Master Netting Arrangement		1	0
Natural gas | Physical purchases/sales | Not Designated as Hedging Instrument | Other Current Assets
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset Including Not Subject to Master Netting Arrangement		2	5
Natural gas | Physical purchases/sales | Not Designated as Hedging Instrument | Other Current Liabilities
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability Including Not Subject to Master Netting Arrangement		0	0
Crude oil (for condensate) | Financial futures/swaps | Not Designated as Hedging Instrument | Other Current Assets
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset Including Not Subject to Master Netting Arrangement		2	1
Crude oil (for condensate) | Financial futures/swaps | Not Designated as Hedging Instrument | Other Current Liabilities
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability Including Not Subject to Master Netting Arrangement		14	19
Crude oil (for condensate) | Financial futures/swaps | Not Designated as Hedging Instrument | Other Noncurrent Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset Including Not Subject to Master Netting Arrangement		0	0
Crude oil (for condensate) | Financial futures/swaps | Not Designated as Hedging Instrument | Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability Including Not Subject to Master Netting Arrangement		2	8
Crude oil (for condensate) | Financial swaptions | Not Designated as Hedging Instrument | Other Current Assets
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset Including Not Subject to Master Netting Arrangement		3	0
Crude oil (for condensate) | Financial swaptions | Not Designated as Hedging Instrument | Other Current Liabilities
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability Including Not Subject to Master Netting Arrangement		0	0
Natural gas liquids | Financial futures/swaps | Not Designated as Hedging Instrument | Other Current Assets
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset Including Not Subject to Master Netting Arrangement		20	25
Natural gas liquids | Financial futures/swaps | Not Designated as Hedging Instrument | Other Current Liabilities
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability Including Not Subject to Master Netting Arrangement		3	3
Natural gas liquids | Financial futures/swaps | Not Designated as Hedging Instrument | Other Noncurrent Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset Including Not Subject to Master Netting Arrangement		2	11
Natural gas liquids | Financial futures/swaps | Not Designated as Hedging Instrument | Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability Including Not Subject to Master Netting Arrangement		$ 0	$ 2

[1] See Note 11 for a reconciliation of the Partnership’s commodity derivatives fair value to the Partnership’s Condensed Consolidated Balance Sheets as of June 30, 2020 and December 31, 2019.

[2] All interest rate derivative instruments that were designated as cash flow hedges are considered Level 2 as of June 30, 2020 and December 31, 2019.