Subsequent Events (Narrative) (Details)
$ / shares in Units, shares in Millions, $ in Millions
3 Months Ended 6 Months Ended
Jul. 30, 2015
USD ($)
$ / shares
Jul. 02, 2015
Jul. 01, 2015
USD ($)
shares
Jun. 30, 2015
USD ($)
Jun. 30, 2014
USD ($)
Jun. 30, 2015
USD ($)
Jun. 30, 2014
USD ($)
Subsequent Event [Line Items]              
Gain on Conveyances       $ 8.3 $ 0.3 $ 13.6 $ 17.8
Subsequent Event [Member]              
Subsequent Event [Line Items]              
Distribution Made to Limited Partner, Distributions Declared, Per Unit | $ / shares $ 0.1675            
Distribution Made to Limited Partner, Cash Distributions Declared $ 16.9            
Distribution Made to Limited Partner, Distribution Date Aug. 20, 2015            
Distribution Made to Limited Partner, Date of Record Aug. 13, 2015            
Share Distribution, Date     Jul. 01, 2015        
Common Stock, Shares Authorized | shares     317.6        
Common Stock, Shares, Issued | shares     317.6        
Distribution Payable Shareholder Date of Record     Jun. 19, 2015        
Stock Trade Date   Jul. 02, 2015          
Acres Conveyed     20,000        
Gain on Conveyances     $ 35.8