v3.5.0.2

Transactions with Affiliates (Schedule of Affiliated Transactions) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Related Party Transaction [Line Items]
Transportation revenues	$ 0.0	$ 18.5	$ 0.0	$ 47.5
Storage revenues	0.0	12.9	0.0	26.2
Other revenues	0.0	0.1	0.0	0.2
Operation and maintenance	0.0	24.9	0.0	52.9
Interest expense	0.0	11.0	0.0	29.3
Interest income	$ 0.0	$ 3.4	$ 0.0	$ 4.4

Midstream refers to those gas industry activities that fall between exploration and production (upstream) and refining and marketing (downstream). It may be applied to the gathering, processing, transmission and storage of natural gas; including the treating of natural gas to remove impurities, along with the sale of by-products such as residue gas, natural gas liquids and condensate with a related party.

+ References

No definition available.

+ Details

Name:	cpgx_NaturalGasMidstreamRevenueRelatedParty
Namespace Prefix:	cpgx_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Revenue from storage facilities, such as a LNG ( Liquefied Natural Gas) storage facility.

+ References

No definition available.

+ Details

Name:	cpgx_NaturalGasStorageRevenueRelatedParties
Namespace Prefix:	cpgx_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of operating expense for routine plant maintenance, repairs and operations of regulated operation.

+ References

No definition available.

+ Details

Name:	cpgx_UtilitiesOperatingExpenseMaintenanceandOperationsRelatedParties
Namespace Prefix:	cpgx_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of interest expense incurred on a debt or other obligation to related party.

+ References

No definition available.

+ Details

Name:	us-gaap_InterestExpenseRelatedParty
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of interest income earned from interest-bearing assets owed to the entity by related party.

+ References

No definition available.

+ Details

Name:	us-gaap_InterestIncomeRelatedParty
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_RelatedPartyTransactionLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Reflects the sum of all other revenue and income realized from sales and other transactions (excluding transactions that are eliminated in consolidated or combined financial statements) with related party during the period.

+ References

No definition available.

+ Details

Name:	us-gaap_RelatedPartyTransactionOtherRevenuesFromTransactionsWithRelatedParty
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Columbia Pipeline Group, Inc. 10-Q