Consolidated Statements of Changes in Equity - USD ($) $ in Millions	Total	Series A Preferred Limited Partners [Member]	Series B Preferred Limited Partners [Member]	Series C Preferred Limited Partners [Member]	Limited Partners	General Partner	Accumulated Other Comprehensive (Loss) Income	Noncontrolling Interests
Beginning balance at Dec. 31, 2018	$ 7,297	$ 489	$ 156	$ 106	$ 6,418	$ 107	$ (8)	$ 29
Increase (Decrease) in Partners' Capital [Roll Forward]
Net income (loss)	76	9	3	2	20	41	0	1
Total Cash Distribution to Unitholders	(159)	0	(3)	(2)	(111)	(43)	0	0
Distributions to noncontrolling interests	(1)	0	0	0	0	0	0	1
Ending balance at Mar. 31, 2019	7,213	498	156	106	6,327	105	(8)	29
Beginning balance at Dec. 31, 2018	7,297	489	156	106	6,418	107	(8)	29
Increase (Decrease) in Partners' Capital [Roll Forward]
Net income (loss)	19
Other comprehensive income	0
Ending balance at Sep. 30, 2019	6,815	499	156	106	5,937	97	(8)	28
Beginning balance at Mar. 31, 2019	7,213	498	156	106	6,327	105	(8)	29
Increase (Decrease) in Partners' Capital [Roll Forward]
Net income (loss)	120	10	3	2	62	42	0	1
Total Cash Distribution to Unitholders	(178)	(18)	(3)	(2)	(112)	(43)	0	0
Distributions to noncontrolling interests	(2)	0	0	0	0	0	0	(2)
Ending balance at Jun. 30, 2019	7,153	490	156	106	6,277	104	(8)	28
Increase (Decrease) in Partners' Capital [Roll Forward]
Net income (loss)	(177)	9	3	3	(228)	35	0	1
Other comprehensive income	0
Total Cash Distribution to Unitholders	(160)	0	(3)	(3)	(112)	(42)	0	0
Distributions to noncontrolling interests	(1)	0	0	0	0	0	0	(1)
Ending balance at Sep. 30, 2019	6,815	499	156	106	5,937	$ 97	(8)	28
Beginning balance at Dec. 31, 2019	6,633	489	156	106	5,861		(7)	28
Increase (Decrease) in Partners' Capital [Roll Forward]
Net income (loss)	(549)	9	3	2	(564)		0	1
Total Cash Distribution to Unitholders	(167)	0	(3)	(2)	(162)		0	0
Distributions to noncontrolling interests	(1)	0	0	0	0		0	(1)
Ending balance at Mar. 31, 2020	5,916	498	156	106	5,135		(7)	28
Beginning balance at Dec. 31, 2019	6,633	489	156	106	5,861		(7)	28
Increase (Decrease) in Partners' Capital [Roll Forward]
Net income (loss)	(389)
Other comprehensive income	0
Ending balance at Sep. 30, 2020	5,882	499	156	106	5,100		(7)	28
Beginning balance at Mar. 31, 2020	5,916	498	156	106	5,135		(7)	28
Increase (Decrease) in Partners' Capital [Roll Forward]
Net income (loss)	48	10	3	2	32		0	1
Total Cash Distribution to Unitholders	(104)	(18)	(3)	(2)	(81)		0	0
Distributions to noncontrolling interests	(1)	0	0	0	0		0	(1)
Ending balance at Jun. 30, 2020	5,859	490	156	106	5,086		(7)	28
Increase (Decrease) in Partners' Capital [Roll Forward]
Net income (loss)	112	9	3	3	96		0	1
Other comprehensive income	0
Total Cash Distribution to Unitholders	(88)	0	(3)	(3)	(82)		0	0
Distributions to noncontrolling interests	(1)	0	0	0	0		0	(1)
Ending balance at Sep. 30, 2020	$ 5,882	$ 499	$ 156	$ 106	$ 5,100		$ (7)	$ 28