Partners' Capital and Distributions (Details 2) - USD ($) shares in Millions, $ in Millions	1 Months Ended	9 Months Ended
	Mar. 31, 2015	Sep. 30, 2015	Sep. 30, 2014
Partners Capital and Distribution
Issuance of common units, net proceeds		$ 1,121	$ 669
SLC Pipeline LLC
Partners Capital and Distribution
Noncontrolling interests in subsidiaries (as a percent)		25.00%
Continuous Offering Program
Partners Capital and Distribution
Issuance of common units (in units)		1.1
Issuance of common units, net proceeds		$ 59
Contribution from general partner		1
Commissions to sales agents		$ 1
Underwritten Offering
Partners Capital and Distribution
Issuance of common units (in units)	21.0
Issuance of common units, net proceeds	$ 1,100
Contribution from general partner	$ 21