Net Income Per Limited Partner Unit - Schedule of Basic and Diluted Net Income Per Unit (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Distribution Made To Limited Partner [Line Items]
Distributions declared	$ 119	$ 106
Income (less than) / in excess of distributions	13	(42)
Net income attributable to the Partnership	132	64
General Partner
Distribution Made To Limited Partner [Line Items]
Distributions declared	26	28
Income (less than) / in excess of distributions	1	(1)
Net income attributable to the Partnership	27	27
Limited Partners’ Common Units
Distribution Made To Limited Partner [Line Items]
Distributions declared	93	78
Income (less than) / in excess of distributions	12	(41)
Net income attributable to the Partnership	$ 105	$ 37
Weighted average units outstanding (in millions)
Weighted average units outstanding, basic and diluted (in shares)	223.8	209.4
Net income per Limited Partner Unit (in dollars)
Net income per Limited Partner unit, basic and diluted (in dollars per share)	$ 0.47	$ 0.18