Net Income Per Limited Partner Unit (Schedule of Net Income Per Limited Partner Unit) (Details) - Jun. 30, 2015 - USD ($)
$ / shares in Units, shares in Millions, $ in Millions
Total
Total
Schedule Of Earnings Per Unit [Line Items]    
Incentive Distribution, Distribution $ 0.0 $ 0.0
Partners' Capital Account, Distributions 16.9 26.1
Undistributed Earnings, Basic (0.6) 3.5
Net Income (Loss) Allocated to Limited Partners $ 16.3 $ 29.6
Weighted Average Number of Shares Outstanding, Basic and Diluted 100.6 100.6
Net Income (Loss), Per Outstanding Limited Partnership and General Partnership Unit, Basic and Diluted, Net of Tax $ 0.16 $ 0.29
Incentive Distribution Rights [Member]    
Schedule Of Earnings Per Unit [Line Items]    
Incentive Distribution, Distribution $ 0.0 $ 0.0
Undistributed Earnings, Basic 0.0 0.0
Net Income (Loss) Allocated to Limited Partners $ 0.0 $ 0.0
Weighted Average Number of Shares Outstanding, Basic and Diluted 0.0 0.0
Net Income (Loss), Per Outstanding Limited Partnership and General Partnership Unit, Basic and Diluted, Net of Tax $ 0.00 $ 0.00
Subordinated Units [Member]    
Schedule Of Earnings Per Unit [Line Items]    
Distribution Made to Limited Partner, Cash Distributions Declared $ 7.9 $ 12.2
Undistributed Earnings, Basic (0.6) 1.3
Net Income (Loss) Allocated to Limited Partners $ 7.3 $ 13.5
Weighted Average Number of Shares Outstanding, Basic and Diluted 46.8 46.8
Net Income (Loss), Per Outstanding Limited Partnership and General Partnership Unit, Basic and Diluted, Net of Tax $ 0.16 $ 0.29
Common Units [Member]    
Schedule Of Earnings Per Unit [Line Items]    
Distribution Made to Limited Partner, Cash Distributions Declared $ 9.0 $ 13.9
Undistributed Earnings, Basic 0.0 2.2
Net Income (Loss) Allocated to Limited Partners $ 9.0 $ 16.1
Weighted Average Number of Shares Outstanding, Basic and Diluted 53.8 53.8
Net Income (Loss), Per Outstanding Limited Partnership and General Partnership Unit, Basic and Diluted, Net of Tax $ 0.17 $ 0.30