Related Party Debt - Additional Information (Details) - USD ($)				12 Months Ended
	May 11, 2018	Feb. 06, 2018	Dec. 01, 2017	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Aug. 06, 2019	Aug. 01, 2018	Jul. 31, 2018	Mar. 01, 2017
Line Of Credit Facility [Line Items]
Interest and fee expenses associated with borrowings				$ 90,000,000	$ 92,000,000	$ 61,000,000
Interest paid				92,000,000	88,000,000	53,000,000
Long-term debt, carrying value				2,694,000,000	2,694,000,000
Long-term debt, fair value				2,928,000,000	2,825,000,000
Repayments of credit facilities				0	0	$ 1,573,000,000
Maximum borrowing capacity				$ 3,590,000,000	3,590,000,000
Seven Year Fixed Facility | Revolving Credit Facility
Line Of Credit Facility [Line Items]
Debt instrument term				7 years
Maximum borrowing capacity				$ 600,000,000	600,000,000
Fixed interest rate				4.06%
Debt issuance costs									$ 1,000,000
Five Year Revolver due July 2023
Line Of Credit Facility [Line Items]
Debt instrument term				5 years
Five Year Revolver due July 2023 | Revolving Credit Facility
Line Of Credit Facility [Line Items]
Debt instrument term				5 years
Repayments of credit facilities		$ 247,000,000
Maximum borrowing capacity				$ 760,000,000	760,000,000			$ 760,000,000
Fixed interest rate								0.19%
Weighted average interest rate				2.06%
Five Year Revolver due December 2022 | Revolving Credit Facility
Line Of Credit Facility [Line Items]
Debt instrument term				5 years
Repayments of credit facilities		$ 726,000,000
Maximum borrowing capacity				$ 1,000,000,000	1,000,000,000
Five Year Revolver due December 2022 | Revolving Credit Facility | Affiliated Entity | Shell Treasury Center West Inc
Line Of Credit Facility [Line Items]
Unused capacity commitment fee percentage			0.19%
Maximum borrowing capacity			$ 1,000,000,000
Debt issuance costs			$ 2,000,000
Weighted average interest rate				2.26%
2019 Zydeco Revolver | Revolving Credit Facility
Line Of Credit Facility [Line Items]
Maximum borrowing capacity				$ 30,000,000	30,000,000
2019 Zydeco Revolver | Revolving Credit Facility | Affiliated Entity | Shell Treasury Center West Inc
Line Of Credit Facility [Line Items]
Maximum borrowing capacity							$ 30,000,000
Fixed interest rate				0.86%
Five Year Fixed Facility | Revolving Credit Facility
Line Of Credit Facility [Line Items]
Debt instrument term				5 years
Maximum borrowing capacity				$ 600,000,000	600,000,000
Five Year Fixed Facility | Revolving Credit Facility | Affiliated Entity | Shell Treasury Center West Inc
Line Of Credit Facility [Line Items]
Maximum borrowing capacity										$ 600,000,000
Fixed interest rate				3.23%
Debt issuance costs										$ 1,000,000
Ten Year Fixed Facility | Revolving Credit Facility
Line Of Credit Facility [Line Items]
Debt instrument term				10 years
Maximum borrowing capacity				$ 600,000,000	$ 600,000,000
Ten Year Fixed Facility | Revolving Credit Facility | Affiliated Entity | Shell Treasury Center West Inc
Line Of Credit Facility [Line Items]
Maximum borrowing capacity				$ 600,000,000
Fixed interest rate				4.18%
May 2018 Acquisition
Line Of Credit Facility [Line Items]
Consideration transferred	$ 1,220,000,000
May 2018 Acquisition | Five Year Revolver due July 2023 | Revolving Credit Facility | Affiliated Entity | Shell Treasury Center West Inc
Line Of Credit Facility [Line Items]
Consideration transferred	494,000,000
May 2018 Acquisition | Five Year Revolver due December 2022 | Revolving Credit Facility | Affiliated Entity | Shell Treasury Center West Inc
Line Of Credit Facility [Line Items]
Consideration transferred	$ 726,000,000