Basis of Accounting Presentation Basis of Accounting Presentation (Details)
3 Months Ended
Mar. 31, 2015
Basis Of Accounting Presentation [Line Items]  
Number Of Customers 3,800,000
Limited Liability Company (LLC) or Limited Partnership (LP), Members or Limited Partners, Ownership Interest 15.70%
Limited Liability Company or Limited Partnership, Managing Member or General Partner, Name CPP GP LLC
Corporate Joint Venture [Member]  
Basis Of Accounting Presentation [Line Items]  
Limited Liability Company (LLC) or Limited Partnership (LP), Managing Member or General Partner, Ownership Interest 84.30%