|
Initial Public Offering (Narrative) (Details) (USD $)
In Millions, except Share data, unless otherwise specified
|
2 Months Ended |
1 Months Ended |
3 Months Ended |
|
Mar. 31, 2015
|
Feb. 11, 2015
|
Mar. 31, 2015
|
| Initial Public Offering [Line Items] |
|
|
|
| Net proceeds from IPO |
$ 1,168.4 |
|
|
| Contribution of capital from parent |
|
1,217.3 |
|
| Underwriting discounts, structuring fees, and offering expenses |
69.8 |
|
|
| Limited Liability Company (LLC) or Limited Partnership (LP), Members or Limited Partners, Ownership Interest |
|
|
15.70% |
| Columbia Energy Group |
|
|
|
| Initial Public Offering [Line Items] |
|
|
|
| Contribution of capital from parent |
|
1,200.0 |
|
| Limited Liability Company (LLC) or Limited Partnership (LP), Members or Limited Partners, Ownership Interest |
7.30% |
|
|
| Columbia OpCo |
|
|
|
| Initial Public Offering [Line Items] |
|
|
|
| Limited Liability Company (LLC) or Limited Partnership (LP), Members or Limited Partners, Ownership Interest Additional Ownership Interest |
8.40% |
|
|
| Limited Liability Company (LLC) or Limited Partnership (LP), Members or Limited Partners, Ownership Interest |
15.70% |
|
|
| Reimbursement of Preformation Capital |
500.0 |
|
|
| Noncontrolling Interest [Member] |
|
|
|
| Initial Public Offering [Line Items] |
|
|
|
| Net proceeds from IPO |
0 |
|
|
| Contribution of capital from parent |
|
0 |
|
| Common Units [Member] |
|
|
|
| Initial Public Offering [Line Items] |
|
|
|
| Partners' Capital Account, Units, Sold in Public Offering |
53,833,107 |
|
|
| Shares Issued, Price Per Share |
|
$ 23.00 |
|
| Common Units [Member] | Over-Allotment Option [Member] |
|
|
|
| Initial Public Offering [Line Items] |
|
|
|
| Partners' Capital Account, Units, Sold in Public Offering |
7,021,709 |
|
|
| Subordinated Units [Member] | Columbia Energy Group |
|
|
|
| Initial Public Offering [Line Items] |
|
|
|
| Partners' Capital Account, Units, Sold in Public Offering |
46,811,398 |
|
|
| Limited Partner [Member] |
|
|
|
| Initial Public Offering [Line Items] |
|
|
|
| Net proceeds from IPO |
1,168.4 |
|
|
| Limited Partner [Member] | Columbia Energy Group |
|
|
|
| Initial Public Offering [Line Items] |
|
|
|
| Limited Liability Company (LLC) or Limited Partnership (LP), Members or Limited Partners, Ownership Interest |
84.30% |
|
|
| Limited Partner [Member] | Common Units [Member] |
|
|
|
| Initial Public Offering [Line Items] |
|
|
|
| Contribution of capital from parent |
|
0 |
|
| Limited Partner [Member] | Subordinated Units [Member] |
|
|
|
| Initial Public Offering [Line Items] |
|
|
|
| Net proceeds from IPO |
0 |
|
|
| Contribution of capital from parent |
|
$ 0 |
|