Partners' Capital and Distributions (Details) - Class A Shares - USD ($) $ / shares in Units, $ in Millions					9 Months Ended
	Nov. 13, 2015	Aug. 14, 2015	May. 15, 2015	Feb. 13, 2015	Sep. 30, 2015
Third quarter 2015 distribution | Subsequent Event
Partners Capital and Distributions
Date declared					Oct. 07, 2015
Distribution Date					Nov. 13, 2015
Distributions to Class A shareholders	$ 52
Distribution per Class A share	$ 0.231
Shareholders of record, date					Oct. 30, 2015
Second quarter 2015 distribution
Partners Capital and Distributions
Date declared					Jul. 07, 2015
Distribution Date					Aug. 14, 2015
Distributions to Class A shareholders		$ 51
Distribution per Class A share		$ 0.227
First quarter 2015 distribution
Partners Capital and Distributions
Date declared					Apr. 07, 2015
Distribution Date					May 15, 2015
Distributions to Class A shareholders			$ 50
Distribution per Class A share			$ 0.222
Fourth quarter 2014 distribution
Partners Capital and Distributions
Date declared					Jan. 08, 2015
Distribution Date					Feb. 13, 2015
Distributions to Class A shareholders				$ 42
Distribution per Class A share				$ 0.203