Statements Of Consolidated and Combined Equity and Partners' Capital Statement of Consolidated and Combined Equity and Partners' Capital (Parenthetical) (USD $)
In Millions, unless otherwise specified
2 Months Ended
Mar. 31, 2015
Net proceeds from IPO $ 1,168.4
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%