Partners' Capital and Distributions (Narrative) (Details) $ in Millions	Jul. 27, 2016 USD ($) $ / units shares	Jul. 22, 2015 USD ($)	Jun. 30, 2016 shares	Dec. 31, 2015 shares
Partners Capital And Distributions [Line Items]
Limited Partners' Capital Account, Units Outstanding			109,979,218	109,979,218
Public sale of units net of offering costs | $		$ 437.2
Class A [Member] | Limited Partner
Partners Capital And Distributions [Line Items]
Limited Partners' Capital Account, Units Outstanding			109,939,221
Class A [Member] | Subsequent Event | Limited Partner
Partners Capital And Distributions [Line Items]
Common units, issued	8,000,000
Unit price | $ / units	37.90
Option to purchase additional units, period	30 days
Option to purchase additional units (in units)	1,200,000
Public sale of units net of offering costs | $	$ 298.0
Class B [Member] | Limited Partner
Partners Capital And Distributions [Line Items]
Limited Partners' Capital Account, Units Outstanding			39,997