Selected Quarterly Financial Data (unaudited) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Total revenues	$ 4,098	$ 4,331	$ 4,475	$ 3,692	$ 3,877	$ 4,761	$ 4,607	$ 3,749	$ 16,596	$ 16,994	$ 11,723
Operating income (loss)	98	117	97	152	(38)	159	128	96	464	345	229
Net Income (loss)	$ 83	$ 66	$ 55	$ 109	$ (72)	$ 112	$ 68	$ (315)	$ 313	$ (207)	$ 149
Common Units [Member]
Income (loss) from continuing operations per limited partner unit:
Common - basic	$ 0.76	$ 0.57	$ 0.44	$ 1.08	$ (1.11)	$ 1.16	$ 0.91	$ (1.11)	$ 2.84	$ (0.25)	$ 2.13
Common - diluted	0.75	0.57	0.43	1.07	(1.11)	1.15	0.90	(1.11)	2.82	(0.25)	2.12
Income (loss) from discontinued operations per limited partner unit:
Common - basic	0	0	0	0	0	(0.03)	(0.32)	(2.63)	0	(3.14)	(1.78)
Common - diluted	$ 0	$ 0	$ 0	$ 0	$ 0	$ (0.03)	$ (0.32)	$ (2.63)	$ 0	$ (3.14)	$ (1.78)