Partners' Capital and Distributions (Narrative) (Details) $ / shares in Units, $ in Millions			12 Months Ended
	Jul. 22, 2015 USD ($) $ / shares shares	Apr. 10, 2015 USD ($) $ / shares shares	Dec. 31, 2014 shares	Sep. 30, 2015 shares
Partners Capital And Distributions [Line Items]
Limited Partners' Capital Account, Units Outstanding			95,029,218	109,979,218
Common units, issued	10,350,000	4,600,000	95,029,218	109,979,218
Sale of Stock, Price Per Share | $ / shares	$ 43.77	$ 44.42
Limited Partners' Capital Accountant, Option To Purchase	1,350,000	600,000
Partners' Capital Account, Public Sale of Units Net of Offering Costs | $	$ 437	$ 198
Class A [Member]
Partners Capital And Distributions [Line Items]
Limited Partners' Capital Account, Units Outstanding				109,939,221
Class B [Member]
Partners Capital And Distributions [Line Items]
Limited Partners' Capital Account, Units Outstanding				39,997
Class Two [Member]
Partners Capital And Distributions [Line Items]
Conversion Feature, Minimum Distribution Coverage Ratio			1.1
Class Three [Member]
Partners Capital And Distributions [Line Items]
Conversion Feature, Minimum Distribution Coverage Ratio			1.1
Class Four [Member]
Partners Capital And Distributions [Line Items]
Conversion Feature, Minimum Distribution Coverage Ratio			1.1