Summary of Significant Accounting Policies Cumulative Effect of Changes due to Adoption of ASU 2014-09 (Details) - USD ($) $ in Millions	Jun. 30, 2018	Jan. 01, 2018	Dec. 31, 2017
Other current assets	$ 62	$ 89	$ 81
Property and equipment, net	1,520	1,557	1,557
Intangible assets, net	(659)	(668)	(768)
Other noncurrent assets	123	84	45
Other noncurrent liabilities	136	126	125
Common Units
Total partners' capital	$ 916	1,893	$ 1,947
Accounting Standards Update 2014-09 [Member]
Other current assets		8
Property and equipment, net		0
Intangible assets, net		(100)
Other noncurrent assets		39
Other noncurrent liabilities		1
Total partners' capital		$ (54)