Net Income (Loss) per Common Unit (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions			3 Months Ended						9 Months Ended
		Oct. 27, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net Income (Loss)			$ (67)	$ 406	$ 435	$ 110	$ 232	$ 385	$ 774	$ 727
Declared distributions			346			323			1,024	949
Assumed allocation of undistributed net loss	[1]		$ (413)			$ (213)			$ (250)	$ (222)
Weighted average units outstanding			414.8			348.6			370.9	348.6
Basic and diluted net income (loss) per unit			$ (0.08)			$ 0.19			$ 1.55	$ 1.38
Common Units [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net Income (Loss)			$ (65)	287	307	$ 77	164	272
Declared distributions			315			217			$ 763	$ 638
Assumed allocation of undistributed net loss	[1]		(347)			(151)			(188)	(157)
Assumed allocation of net income (loss)			$ (32)			$ 66			$ 575	$ 481
Weighted average units outstanding			414.8			348.6			370.9	348.6
Basic and diluted net income (loss) per unit			$ (0.08)			$ 0.19			$ 1.55	$ 1.38
Common Units [Member] | Subsequent Event [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Distribution Made to Limited Partner, Distributions Declared, Per Unit		$ 0.650
Subordinated Units [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net Income (Loss)			$ (1)	111	119	$ 30	64	105
Declared distributions			0			84			$ 174	$ 248
Assumed allocation of undistributed net loss	[1]		(58)			(58)			(57)	(61)
Assumed allocation of net income (loss)			$ (58)			$ 26			$ 117	$ 187
Weighted average units outstanding			69.2			135.4			113.1	135.4
Basic and diluted net income (loss) per unit			$ (0.84)			$ 0.19			$ 1.03	$ 1.38
General Partner [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net Income (Loss)			$ (1)	$ 8	$ 9	$ 3	$ 4	$ 8
Declared distributions			6			6			$ 20	$ 19
Assumed allocation of undistributed net loss	[1]		(8)			(4)			(5)	(4)
Assumed allocation of net income (loss)			(2)			2			15	15
IDR [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Declared distributions			25			16			67	44
Assumed allocation of undistributed net loss	[1]		0			0			0	0
Assumed allocation of net income (loss)			$ 25			$ 16			$ 67	$ 44

[1] Under our partnership agreement, the IDRs participate in net income only to the extent of the amount of cash distributions actually declared, thereby excluding the IDRs from participating in undistributed net income.