Derivative Instruments and Hedging Activities - Balance Sheet Location (Details) bbl in Millions, $ in Millions		12 Months Ended
		Dec. 31, 2019 USD ($) bbl	Mar. 31, 2020 USD ($)
Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability Including Not Subject to Master Netting Arrangement	[1]	$ 3	$ 9
Derivative Asset, Fair Value, Gross Asset Including Not Subject to Master Netting Arrangement	[1]	0	0
Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability Including Not Subject to Master Netting Arrangement	[2]	38	26
Derivative Asset, Fair Value, Gross Asset Including Not Subject to Master Netting Arrangement	[2]	49	47
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		1	5
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		2	4
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		5	6
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		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		5	4
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
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		$ 0	2
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			1
Derivative, Nonmonetary Notional Amount, Volume | bbl		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		$ 1	6
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		19	8
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	1
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		8	5
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		0	4
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		25	16
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	5
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		11	6
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		2	1
Natural gas liquids | 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		0	1
Natural gas liquids | 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

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

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