Subsequent Event (Narrative) (Details) - USD ($)
$ / shares in Units, $ in Millions |
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3 Months Ended |
Feb. 16, 2016 |
Jan. 29, 2016 |
Dec. 31, 2015 |
Sep. 30, 2015 |
Jun. 30, 2015 |
Mar. 31, 2015 |
[1] |
| Subsequent Event [Line Items] |
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| Distribution Made to Limited Partner, Distributions Declared, Per Unit |
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$ 0.1800
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$ 0.1725
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$ 0.1675
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$ 0.0912
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| Distribution Made to Limited Partner, Distribution Date |
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Feb. 19, 2016
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Nov. 20, 2015
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Aug. 20, 2015
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May 20, 2015
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| Distribution Made to Limited Partner, Date of Record |
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Feb. 11, 2016
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Nov. 13, 2015
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Aug. 13, 2015
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May 13, 2015
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| Distribution Made to Limited Partner, Cash Distributions Paid |
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$ 18.1
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$ 17.4
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$ 16.9
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$ 9.2
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| Subsequent Event |
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| Subsequent Event [Line Items] |
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| Distribution Made to Limited Partner, Distributions Declared, Per Unit |
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$ 0.1800
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| Distribution Made to Limited Partner, Cash Distributions Declared |
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$ 18.1
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| Distribution Made to Limited Partner, Distribution Date |
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Feb. 19, 2016
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| Distribution Made to Limited Partner, Date of Record |
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Feb. 11, 2016
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| Distribution Made to Limited Partner, Cash Distributions Paid |
$ 129.2
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| Columbia Energy Group | Subsequent Event |
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| Subsequent Event [Line Items] |
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| Distribution Made to Limited Partner, Cash Distributions Paid |
108.9
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| Columbia Pipeline Partners LP | Subsequent Event |
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| Subsequent Event [Line Items] |
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| Distribution Made to Limited Partner, Cash Distributions Paid |
$ 20.3
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