Statement of Consolidated and Combined Equity and Partners' Capital (Parenthetical) - Jun. 30, 2015 - Scenario, Unspecified [Domain] - USD ($)
$ in Millions
Total
Net proceeds from IPO $ 1,168.4
Common Units [Member] | Limited Partner [Member]  
Net proceeds from IPO $ 1,168.4
Columbia OpCo  
Limited Liability Company (LLC) or Limited Partnership (LP), Members or Limited Partners, Ownership Interest Additional Ownership Interest 8.40%
Hardy Storage [Member]  
Equity Method Investment, Percent Not Contributed to Partnership 1.00%
Equity Method Investment, Ownership Percentage 50.00%