Columbia Pipeline Partners (CPPL) 10-Q 3 Aug 15 2015 Q2 Quarterly report Financial data

Document And Entity Information

Document And Entity Information - shares	6 Months Ended
	Jun. 30, 2015	Jul. 27, 2015
Document Information [Line Items]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2015
Document Fiscal Year Focus	2,015
Document Fiscal Period Focus	Q2
Entity Registrant Name	COLUMBIA PIPELINE PARTNERS LP/DE
Entity Central Index Key	1,420,783
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Common Units [Member]
Document Information [Line Items]
Entity Units Outstanding		53,834,784
Subordinated Units [Member]
Document Information [Line Items]
Entity Units Outstanding		46,811,398

Statements of Consolidated and

Statements of Consolidated and Combined Balance Sheets - USD ($) $ in Millions		Jun. 30, 2015	Dec. 31, 2014
Current Assets
Cash and cash equivalents		$ 136.1	$ 0.5
Accounts receivable (less reserve of $0.3 and $0.3, respectively)		123.5
Accounts receivable-affiliated		656.7
Materials and supplies, at average cost		28.2
Exchange gas receivable		24.8
Regulatory assets		5.3
Deferred property taxes		32.3
Deferred income taxes		0
Prepayments and other		10.1
Total Current Assets		1,017
Investments
Unconsolidated affiliates		443.5
Other investments		5.6
Total Investments		449.1
Property, Plant and Equipment
Property, plant and equipment		8,394.7
Accumulated depreciation and amortization		(2,968.1)
Net Property, Plant and Equipment		5,426.6
Other Noncurrent Assets
Regulatory assets		125.1
Goodwill		1,975.5
Postretirement and postemployment benefits assets		117
Deferred charges and other		10.8
Total Other Noncurrent Assets		2,228.4
Total Assets		9,121.1
Current Liabilities
Current portion of long-term debt-affiliated		0
Short-term borrowings		20
Short-term borrowings-affiliated		67.1
Accounts payable		66
Accounts payable-affiliated		41.5
Customer deposits		41.6
Taxes accrued		78.3
Exchange gas payable		24.4
Deferred revenue		13.7
Regulatory liabilities		9
Legal and environmental		1.6
Accrued capital expenditures		146.3
Other accruals		65.8
Total Current Liabilities		575.3
Noncurrent Liabilities
Long-term debt-affiliated		630.9
Deferred income taxes		1
Accrued liability for postretirement and postemployment benefits		37.4
Regulatory liabilities		292
Asset retirement obligations		23.8	23.2
Other noncurrent liabilities		57.6
Total Noncurrent Liabilities		1,042.7
Total Liabilities		1,618
Equity and Partners' Capital
Net parent investment		0
Accumulated other comprehensive loss	[1]	(4.1)	(16.7)
Total Columbia Pipeline Partners LP partners' equity and capital		1,247.6
Noncontrolling Interest in Columbia OpCo		6,255.5
Total Equity and Partners' Capital		7,503.1	4,171.3
Total Liabilities and Equity and Partners' Capital		9,121.1
Predecessor [Member]
Current Assets
Cash and cash equivalents			0.5
Accounts receivable (less reserve of $0.3 and $0.3, respectively)			149.3
Accounts receivable-affiliated			153.8
Materials and supplies, at average cost			24.9
Exchange gas receivable			34.8
Regulatory assets			6.1
Deferred property taxes			48.9
Deferred income taxes			24.6
Prepayments and other			14.8
Total Current Assets			457.7
Investments
Unconsolidated affiliates			444.3
Other investments			6.2
Total Investments			450.5
Property, Plant and Equipment
Property, plant and equipment			7,931.6
Accumulated depreciation and amortization			(2,971.4)
Net Property, Plant and Equipment			4,960.2
Other Noncurrent Assets
Regulatory assets			151.9
Goodwill			1,975.5
Postretirement and postemployment benefits assets			102.7
Deferred charges and other			9
Total Other Noncurrent Assets			2,239.1
Total Assets			8,107.5
Current Liabilities
Current portion of long-term debt-affiliated			115.9
Short-term borrowings			0
Short-term borrowings-affiliated			247.3
Accounts payable			56.1
Accounts payable-affiliated			49.9
Customer deposits			13.4
Taxes accrued			106.9
Exchange gas payable			34.7
Deferred revenue			22.2
Regulatory liabilities			1.3
Legal and environmental			1.5
Accrued capital expenditures			61.1
Other accruals			67.4
Total Current Liabilities			777.7
Noncurrent Liabilities
Long-term debt-affiliated			1,472.8
Deferred income taxes			1,239
Accrued liability for postretirement and postemployment benefits			44.7
Regulatory liabilities			294.3
Asset retirement obligations			23.2
Other noncurrent liabilities			84.5
Total Noncurrent Liabilities			3,158.5
Total Liabilities			3,936.2
Equity and Partners' Capital
Net parent investment			4,188
Accumulated other comprehensive loss			(16.7)
Total Columbia Pipeline Partners LP partners' equity and capital			4,171.3
Noncontrolling Interest in Columbia OpCo			0
Total Equity and Partners' Capital			4,171.3
Total Liabilities and Equity and Partners' Capital			8,107.5
Common Units [Member]
Equity and Partners' Capital
Limited Partners' Capital Account		952.7
Common Units [Member] | Predecessor [Member]
Equity and Partners' Capital
Limited Partners' Capital Account			0
Subordinated Units [Member]
Equity and Partners' Capital
Limited Partners' Capital Account		$ 299
Subordinated Units [Member] | Predecessor [Member]
Equity and Partners' Capital
Limited Partners' Capital Account			$ 0
[1]	All amounts prior to the IPO are net of tax. Amounts in parentheses indicate debits.

Statements of Consolidated and3

Statements of Consolidated and Combined Balance Sheets (Parenthetical) - USD ($) $ in Millions	Jun. 30, 2015	Dec. 31, 2014
Accounts receivable less reserve	$ 0.3
Predecessor [Member]
Accounts receivable less reserve		$ 0.3
Common Units [Member]
Limited Partners' Capital Account, Units Issued	53,834,784	0
Limited Partners' Capital Account, Units Outstanding	53,834,784	0
Subordinated Units [Member]
Limited Partners' Capital Account, Units Issued	46,811,398	0
Limited Partners' Capital Account, Units Outstanding	46,811,398	0

Statements Of Consolidated and4

Statements Of Consolidated and Combined Operations - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Operating Revenues
Transportation revenues	$ 237.3		$ 485.2
Transportation revenues-affiliated	18.4		47.1
Storage revenues	36.2		72.8
Storage revenues-affiliated	12.9		26.2
Other revenues	10.8		23.5
Total Operating Revenues	315.6		654.8
Operating Expenses
Operation and maintenance	138		248
Operation and maintenance-affiliated	38.6		74.7
Depreciation and amortization	33		65.3
Gain on sale of assets	(8.3)		(13.6)
Property and other taxes	19.1		38.1
Total Operating Expenses	220.4		412.5
Equity Earnings in Unconsolidated Affiliates	14		28.9
Operating Income	109.2		271.2
Other Income (Deductions)
Interest expense-affiliated	(6.3)		(17.7)
Other, net	4.9		9.2
Total Other Deductions, net	(1.4)		(8.5)
Income before Income Taxes	107.8		262.7
Income Taxes	0		23.7
Net Income	107.8		239
Income (Loss) Attributable to Noncontrolling Interest	91.5		166.7
Net Income (Loss) Allocated to Limited Partners	$ 16.3		$ 29.6
Net income attributable to partners' ownership interest subsequent to IPO per limited partner unit (basic and diluted)
Net Income (Loss), Per Outstanding Limited Partnership and General Partnership Unit, Basic and Diluted, Net of Tax	$ 0.16		$ 0.29
Weighted average limited partner units outstanding (basic and diluted)
Weighted Average Number of Shares Outstanding, Basic and Diluted	100.6		100.6
Predecessor [Member]
Operating Revenues
Transportation revenues		$ 260.5		$ 507.4
Transportation revenues-affiliated		18.9		47.5
Storage revenues		36		72.3
Storage revenues-affiliated		13.2		26.9
Other revenues		14.8		34.8
Total Operating Revenues		343.4		688.9
Operating Expenses
Operation and maintenance		176.1		313.9
Operation and maintenance-affiliated		29.5		57.8
Depreciation and amortization		28.8		58.5
Gain on sale of assets		(0.3)		(17.8)
Property and other taxes		17.2		35.7
Total Operating Expenses		251.3		448.1
Equity Earnings in Unconsolidated Affiliates		11.1		20.9
Operating Income		103.2		261.7
Other Income (Deductions)
Interest expense-affiliated		(12.6)		(24.7)
Other, net		2.6		4.4
Total Other Deductions, net		(10)		(20.3)
Income before Income Taxes		93.2		241.4
Income Taxes		34.2		89.9
Net Income		$ 59		$ 151.5
Common Units [Member]
Other Income (Deductions)
Net Income (Loss) Allocated to Limited Partners	$ 9		$ 16.1
Net income attributable to partners' ownership interest subsequent to IPO per limited partner unit (basic and diluted)
Net Income (Loss), Per Outstanding Limited Partnership and General Partnership Unit, Basic and Diluted, Net of Tax	$ 0.17		$ 0.30
Weighted average limited partner units outstanding (basic and diluted)
Weighted Average Number of Shares Outstanding, Basic and Diluted	53.8		53.8
Subordinated Units [Member]
Other Income (Deductions)
Net Income (Loss) Allocated to Limited Partners	$ 7.3		$ 13.5
Net income attributable to partners' ownership interest subsequent to IPO per limited partner unit (basic and diluted)
Net Income (Loss), Per Outstanding Limited Partnership and General Partnership Unit, Basic and Diluted, Net of Tax	$ 0.16		$ 0.29
Weighted average limited partner units outstanding (basic and diluted)
Weighted Average Number of Shares Outstanding, Basic and Diluted	46.8		46.8

Statements of Consolidated and5

Statements of Consolidated and Combined Comprehensive Income - USD ($) $ in Millions		1 Months Ended	3 Months Ended			5 Months Ended	6 Months Ended
		Feb. 11, 2015	Jun. 30, 2015		Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2015	Jun. 30, 2014
Net Income		$ 42.7	$ 107.8			$ 196.3	$ 239
Net unrealized gain on cash flow hedges	[1]		0.5				0.6
Other Comprehensive Income, Net of Tax and Transaction Adjustments			0.5				0.6
Total other comprehensive income		0.1	0.5	[2]		0.5		$ 0.6	[2]
Total comprehensive income subsequent to IPO		$ 42.8	108.3			196.8	$ 239.6
Less: Comprehensive income attributable to noncontrolling interest subsequent to IPO			91.9			167.1
Comprehensive income attributable to limited partners subsequent to IPO			$ 16.4			$ 29.7
Predecessor [Member]
Net Income					$ 59			151.5
Net unrealized gain on cash flow hedges	[1]				0.2			0.5
Total other comprehensive income	[2]				0.2			0.5
Total comprehensive income subsequent to IPO					$ 59.2			$ 152
[1]	Net unrealized gains on derivatives qualifying as cash flow hedges, net of zero and $0.1 million tax expense in the second quarter of 2015 and 2014, respectively, and $0.1 million and $0.3 million tax expense for the six months ended June 30, 2015 and 2014 respectively.
[2]	All amounts prior to the IPO are net of tax. Amounts in parentheses indicate debits.

Statements of Consolidated and6

Statements of Consolidated and Combined Comprehensive Income (Parenthetical) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Predecessor [Member]
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Tax	$ 0.1	$ (0.1)	$ (0.3)

Statements Of Consolidated and7

Statements Of Consolidated and Combined Cash Flows - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
Operating Activities
Net Income	$ 239
Adjustments to Reconcile Net Income to Net Cash from Operating Activities:
Depreciation and amortization	65.3
Deferred income taxes and investment tax credits	10.5
Deferred revenue	(0.1)
Equity-based compensation expense and 401(k) profit sharing contribution	3.6
Gain on sale of assets	(13.6)
Income from unconsolidated affiliates	(28.9)
Amortization of Financing Costs	0.2
AFUDC equity	(8.4)
Distributions of earnings received from equity investees	27.9
Changes in Assets and Liabilities:
Accounts receivable	13.9
Accounts receivable-affiliated	17.1
Accounts payable	1
Accounts payable-affiliated	(14.7)
Customer deposits	1
Taxes accrued	(10.2)
Exchange gas receivable/payable	0.3
Other accruals	(4.5)
Prepayments and other current assets	17
Regulatory assets/liabilities	25.5
Postretirement and postemployment benefits	(13.5)
Deferred charges and other noncurrent assets	(1.9)
Other noncurrent liabilities	(1.6)
Net Cash Flows from Operating Activities	324.9
Investing Activities
Capital expenditures	(430.6)
Insurance recoveries	2.1
Change in short-term lendings-affiliated	(527.1)
Proceeds from disposition of assets	19
Distributions from (contributions to) equity investees	2.2
Other investing activities	(13.4)
Net Cash Flows used for Investing Activities	(947.8)
Financing Activities
Change in short-term borrowings	20
Change in short-term borrowings-affiliated	(180.2)
Issuance of long-term debt-affiliated	0
Payments of long-term debt-affiliated, including current portion	(957.8)
Proceeds from the issuance of common units, net of offering costs	1,168.4
Distribution of IPO proceeds to parent	(500)
Contribution of capital from parent	1,217.3
Partners' Capital Account, Distributions	(9.2)
Net Cash Flows from Financing Activities	758.5
Change in cash and cash equivalents	135.6
Cash and cash equivalents at beginning of period	0.5
Cash and Cash Equivalents at End of Period	136.1
Predecessor [Member]
Operating Activities
Net Income		$ 151.5
Adjustments to Reconcile Net Income to Net Cash from Operating Activities:
Depreciation and amortization		58.5
Deferred income taxes and investment tax credits		47.4
Deferred revenue		2
Equity-based compensation expense and 401(k) profit sharing contribution		1.7
Gain on sale of assets		(17.8)
Income from unconsolidated affiliates		(20.9)
Amortization of Financing Costs		0
AFUDC equity		(4.3)
Distributions of earnings received from equity investees		12.9
Changes in Assets and Liabilities:
Accounts receivable		(25.2)
Accounts receivable-affiliated		19
Accounts payable		24.2
Accounts payable-affiliated		(17.7)
Customer deposits		75.2
Taxes accrued		(11.1)
Exchange gas receivable/payable		4.7
Other accruals		4.3
Prepayments and other current assets		20.4
Regulatory assets/liabilities		25.6
Postretirement and postemployment benefits		(8.9)
Deferred charges and other noncurrent assets		(3.2)
Other noncurrent liabilities		(0.8)
Net Cash Flows from Operating Activities		337.5
Investing Activities
Capital expenditures		(296.6)
Insurance recoveries		6.8
Change in short-term lendings-affiliated		(10.4)
Proceeds from disposition of assets		4.9
Distributions from (contributions to) equity investees		(54.8)
Other investing activities		(3.4)
Net Cash Flows used for Investing Activities		(353.5)
Financing Activities
Change in short-term borrowings		0
Change in short-term borrowings-affiliated		(312.6)
Issuance of long-term debt-affiliated		328.4
Payments of long-term debt-affiliated, including current portion		0
Proceeds from the issuance of common units, net of offering costs		0
Distribution of IPO proceeds to parent		0
Contribution of capital from parent		0
Partners' Capital Account, Distributions		0
Net Cash Flows from Financing Activities		15.8
Change in cash and cash equivalents		(0.2)
Cash and cash equivalents at beginning of period	$ 0.5	0.3
Cash and Cash Equivalents at End of Period		$ 0.1

Statements Of Consolidated and8

Statements Of Consolidated and Combined Equity and Partners' Capital - USD ($) $ in Millions		Total	Noncontrolling Interest [Member]	Accumulated Other Comprehensive Income (Loss)	Parent [Member]	Common Units [Member]Limited Partner [Member]	Subordinated Units [Member]Limited Partner [Member]
Beginning Balance (Predecessor [Member]) at Dec. 31, 2014		$ 4,171.3			$ 4,188
Beginning Balance at Dec. 31, 2014		4,171.3	$ 0	$ (16.7)		$ 0	$ 0
Net Income | Predecessor [Member]					42.7
Net Income		42.7	0	0		0	0
Other Comprehensive Income (Loss), Net of Tax | Predecessor [Member]					0
Other Comprehensive Income (Loss), Net of Tax		0.1	0	0.1		0	0
Contribution of capital from parent | Predecessor [Member]					1,217.3
Contribution of capital from parent		1,217.3	0	0		0	0
Predecessor net tax liabilities not assumed by Columbia OpCo | Predecessor [Member]	[1]				1,232.5
Predecessor net tax liabilities not assumed by Columbia OpCo	[1]	1,222.2	0	(10.3)		0	0
Contributed/Noncontributed Net Parent Investment Adjustments | Predecessor [Member]	[2]				(7.7)
Contributed/Noncontributed Net Parent Investment Adjustments	[2]	(7.7)	0	0		0	0
Distribution to the noncontrolling interest in Columbia OpCo | Predecessor [Member]					0
Distribution to the noncontrolling interest in Columbia OpCo		(500)	(500)	0		0	0
Ending Balance (Predecessor [Member]) at Feb. 11, 2015					6,672.8
Ending Balance at Feb. 11, 2015		6,645.9	0	(26.9)		0	0
Beginning Balance (Predecessor [Member]) at Dec. 31, 2014		4,171.3			4,188
Beginning Balance at Dec. 31, 2014		4,171.3	0	(16.7)		0	0
Net Income		239
Predecessor net tax liabilities not assumed by Columbia OpCo	[1],[3]			(10.3)
Allocation of Accumulated Other Comprehensive Loss To Noncontrolling Interest	[3]	(22.3)
Ending Balance (Predecessor [Member]) at Jun. 30, 2015					0
Ending Balance at Jun. 30, 2015		7,503.1	6,255.5	(4.1)		952.7	299
Beginning Balance (Predecessor [Member]) at Feb. 11, 2015					6,672.8
Beginning Balance at Feb. 11, 2015		6,645.9	0	(26.9)		0	0
Net Income | Predecessor [Member]					0
Net Income		196.3	166.7	0		16.1	13.5
Other Comprehensive Income (Loss), Net of Tax | Predecessor [Member]					0
Other Comprehensive Income (Loss), Net of Tax		0.5	0.4	0.1		0	0
Allocation of Net Investment to Unitholders | Predecessor [Member]					(6,672.8)
Allocation of Net Investment to Unitholders		0	6,185.7	0		0	487.1
Allocation of Accumulated Other Comprehensive Loss To Noncontrolling Interest | Predecessor [Member]					0
Allocation of Accumulated Other Comprehensive Loss To Noncontrolling Interest		0	(22.7)	22.7		0	0
Net proceeds from IPO | Predecessor [Member]					0
Net proceeds from IPO		1,168.4	0	0		1,168.4	0
Purchase of additional interest in Columbia OpCo | Predecessor [Member]	[4]				0
Purchase of additional interest in Columbia OpCo	[4]	0	424.4	0		(227.1)	(197.3)
Limited Partners' Capital Account, Distribution Amount | Predecessor [Member]					0
Limited Partners' Capital Account, Distribution Amount		(9.2)	0	0		(4.9)	(4.3)
Transfers from parent | Predecessor [Member]					0
Transfers from parent		1.2	1	0		0.2	0
Ending Balance (Predecessor [Member]) at Jun. 30, 2015					$ 0
Ending Balance at Jun. 30, 2015		$ 7,503.1	$ 6,255.5	$ (4.1)		$ 952.7	$ 299
[1]	Reflects the non-cash elimination of all historical current and deferred income taxes other than Tennessee state income taxes that continue to be borne by the Partnership post-IPO, as well as associated regulatory assets and liabilities.
[2]	Reflects the removal of amounts related to Crossroads Pipeline Company, Columbia Pipeline Group Services Company, Central Kentucky Transmission Company and 1% of the 50% interest in Hardy Storage that were included in the Predecessor but were not contributed to the Partnership, as well as the inclusion of CNS Microwave, which was not part of the Predecessor.
[3]	All amounts prior to the IPO are net of tax. Amounts in parentheses indicate debits.
[4]	Represents the purchase of an additional 8.4% limited partner interest in Columbia OpCo, recorded at the historical carrying value of Columbia OpCo’s net assets after giving effect to the $1,168.4 million equity contribution. This decreases common unitholders and subordinated unitholders equity by the same amount it increases noncontrolling interest because the MLP's purchase price for its additional 8.4% interest in Columbia OpCo exceeded book value.

Statement of Consolidated and C

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%

Basis of Accounting Presentatio

Basis of Accounting Presentation	6 Months Ended
	Jun. 30, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Accounting Presentation	Basis of Accounting Presentation Columbia Pipeline Partners LP (the "Partnership") was formed in Delaware on December 5, 2007 as a subsidiary of NiSource. NiSource is a Delaware corporation and holding company whose subsidiaries provide natural gas, electricity and other products and services to approximately 3.8 million customers located within a corridor that runs from the Gulf Coast through the Midwest to New England. On February 11, 2015, NiSource contributed its subsidiary CEG to CPG. CEG owns and operates, through its subsidiaries, substantially all of the natural gas transmission and storage assets of NiSource. CEG owns the general partner of the Partnership and all of the Partnership’s incentive distribution rights. Columbia Pipeline Partners LP Predecessor (the “Predecessor”) is comprised of NiSource’s Columbia Pipeline Group Operations reportable segment. The Partnership is engaged in regulated interstate gas transportation and storage services for LDCs, marketers, producers and industrial and commercial customers located in northeastern, mid-Atlantic, midwestern and southern states and the District of Columbia along with unregulated businesses that include midstream services, including gathering, treating, conditioning, processing, compression and liquids handling, and development of mineral rights positions. The regulated services are performed under tariffs at rates subject to FERC approval. Concurrent with the completed IPO, refer to Note 2 for a discussion of IPO results, NiSource contributed substantially all of the assets and operations of the Predecessor to Columbia OpCo, a Delaware limited partnership formed by CEG, which, prior to the Separation, was a wholly owned subsidiary of NiSource and OpCo GP, a wholly owned subsidiary of the Partnership. The contribution is considered to be a reorganization of entities under common control. Subsequent to the IPO, the Partnership owns a 15.7% limited partner interest in Columbia OpCo and CEG owns the remaining 84.3% limited partner interest. MLP GP, a wholly owned subsidiary of CEG, serves as the general partner of the Partnership. OpCo GP serves as the general partner of Columbia OpCo. Columbia Pipeline Group Services Company provides services to the Partnership pursuant to an omnibus agreement. MLP GP, the Partnership, Columbia OpCo and OpCo GP have all adopted a fiscal year end of December 31. Through our ownership of Columbia OpCo’s general partner, we control all of Columbia OpCo’s assets and operations. As a result, the Partnership consolidates Columbia OpCo and CEG's retained interest of 84.3% is recorded as noncontrolling interest in the Partnership's consolidated financial statements. For periods subsequent to the closing of the IPO, the financial statements included in this quarterly report are the financial statements and accounting records of the Partnership. For periods prior to the closing of the IPO, the financial statements included in this quarterly report are the financial statements and accounting records of the Predecessor. The consolidated and combined financial statements were prepared as follows: • The Condensed Consolidated and Combined Balance Sheets (unaudited) consists of the consolidated balance sheet of the Partnership as of June 30, 2015 and the combined balance sheet consists of the Predecessor as of December 31, 2014 . • The Condensed Statement of Consolidated and Combined Operations (unaudited) consists of consolidated results of the Partnership for the three months ended June 30, 2015 and the combined results of the Predecessor for the three months ended June 30, 2014 . • The Condensed Statement of Consolidated and Combined Operations (unaudited) consists of consolidated results of the Partnership for the period from February 11, 2015 through June 30, 2015 and the combined results of the Predecessor for the period from January 1, 2015 through February 10, 2015 and for the six months ended June 30, 2014 . • The Condensed Statement of Consolidated and Combined Comprehensive Income (unaudited) consists of consolidated results of the Partnership for the three months ended June 30, 2015 and the combined results of the Predecessor for the three months ended June 30, 2014 . • The Condensed Statement of Consolidated and Combined Comprehensive Income (unaudited) consists of consolidated results of the Partnership for the period from February 11, 2015 through June 30, 2015 and the combined results of the Predecessor for the period from January 1, 2015 through February 10, 2015 and for the six months ended June 30, 2014 . • The Condensed Statement of Consolidated and Combined Cash Flows (unaudited) consists of consolidated cash flows of the Partnership for the period from February 11, 2015 through June 30, 2015 and the combined cash flows of the Predecessor for the period from January 1, 2015 through February 10, 2015 and for the six months ended June 30, 2014 . • The Condensed Statement of Consolidated and Combined Equity and Partners' Capital (unaudited) consists of consolidated activity of the Partnership for the period from February 11, 2015 through June 30, 2015 and the combined activity of the Predecessor for the period from January 1, 2015 through February 10, 2015. The Condensed Consolidated and Combined Financial Statements (unaudited) have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission. Certain information and note disclosures normally included in annual financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to those rules and regulations, although the Partnership believes that the disclosures made are adequate to make the information not misleading. These financial statements should be read in conjunction with the Predecessor’s combined financial statements included in the Partnership's Annual Report on Form 10-K for the year ended December 31, 2014 (the "2014 Form 10-K"). These financial statements reflect all normal recurring adjustments that are, in the opinion of management, necessary to fairly present the Partnership’s results of operations and financial position in accordance with GAAP in the United States of America. Amounts reported in the Condensed Statement of Consolidated and Combined Operations (unaudited) are not necessarily indicative of amounts expected for the respective annual periods. On June 2, 2015 , NiSource's board of directors approved the separation of CPG and NiSource (the "Separation"). On July 1, 2015, all the shares of CPG were distributed by NiSource to holders of NiSource common stock, and CPG became an independent publicly traded company. Following the Separation, CPG continues to indirectly own MLP GP, our general partner, 84.3% of the limited partner interests in Columbia OpCo and the limited partner interests in the Partnership that are not owned by the public.

Initial Public Offering

Initial Public Offering	6 Months Ended
	Jun. 30, 2015
Equity [Abstract]
Initial Public Offering	Initial Public Offering On February 6, 2015, the Partnership's common units began trading on the New York Stock Exchange under the ticker symbol "CPPL." On February 11, 2015 the Partnership completed its offering of 53,833,107 common units at a price to the public of $23.00 per unit, including 7,021,709 common units that were issued pursuant to the exercise in full of the underwriters' over-allotment option. The Partnership received net proceeds of $1,168.4 million from the offering. At or prior to the closing of the offering the following transactions occurred: • CEG contributed $1,217.3 million of capital to certain subsidiaries of the Predecessor to repay intercompany debt owed to NiSource Finance. CEG entered into new intercompany debt agreements with NiSource Finance for $1,217.3 million ; • CEG contributed substantially all of the subsidiaries in the Predecessor to Columbia OpCo; • CEG assumed responsibility for all historical current and deferred income taxes other than Tennessee state income taxes that continue to be borne by the Partnership post-IPO, as well as associated regulatory assets and liabilities; • CEG contributed a 7.3% limited partner interest in Columbia OpCo in exchange for 46,811,398 subordinated units in the Partnership and all of the Partnership's incentive distribution rights; • the Partnership purchased from Columbia OpCo an additional 8.4% limited partner interest in exchange for $1,168.4 million from the net proceeds of the IPO, net of underwriting discounts, structuring fees and offering expenses of approximately $69.8 million , resulting in the Partnership owning a 15.7% limited partner interest in Columbia OpCo; The table below summarizes the effects of the changes in the Partnership's ownership interest in Columbia OpCo on the Partnership's equity: Three Months Ended Six Months Ended June 30, (in millions) 2015 2015 Net income attributable to the Partnership $ 16.3 $ 29.6 Decrease in partnership equity for the purchase of an additional 8.4 percent interest in Columbia OpCo — (424.4 ) Change from net income attributable to the Partnership and transfers to noncontrolling interest $ 16.3 $ (394.8 ) • Columbia OpCo distributed $500.0 million to CEG as a reimbursement of preformation capital expenditures with respect to the assets contributed to Columbia OpCo. The Partnership entered into an omnibus agreement with CEG and its affiliates at the closing of the IPO that addresses (1) centralized corporate, general and administrative services to be provided by CEG for the Partnership and the reimbursement by the Partnership for the Partnership's portion of these services, (2) the Partnership's right of first offer for CEG's 84.3% interest in Columbia OpCo, (3) the indemnification of the Partnership for certain potential environmental and toxic tort claims losses and expenses associated with the operation of the assets and occurring before the closing date of the IPO and (4) Columbia OpCo's requirement to guarantee future indebtedness that CPG incurs.

Recent Accounting Pronouncement

Recent Accounting Pronouncements	6 Months Ended
	Jun. 30, 2015
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
Recent Accounting Pronouncements	Recent Accounting Pronouncements In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers (Topic 606). ASU 2014-09 outlines a single, comprehensive model for entities to use in accounting for revenue arising from contracts with customers and supersedes most current revenue recognition guidance. The core principle of the new standard is that an entity should recognize revenue to depict the transfer of goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. In July 2015, the FASB extended the adoption date for ASU 2014-09 to periods beginning after December 15, 2017, including interim periods, and the new standard is to be applied retrospectively with early adoption not permitted. The Partnership is currently evaluating the impact the adoption of ASU 2014-09 will have on the Condensed Consolidated and Combined Financial Statements (unaudited) or Notes to Condensed Consolidated and Combined Financial Statements (unaudited). In April 2015, the FASB issued ASU 2015-06, Earnings Per Share (Topic 260): Effects on Historical Earnings per Unit of Master Limited Partnership Dropdown Transactions. ASU 2015-06 specifies that for purposes of calculating historical earnings per unit under the two-class method, the earnings (losses) of a transferred business before the date of a dropdown transaction should be allocated entirely to the general partner. Qualitative disclosures about how the rights to the earnings (losses) differ before and after the dropdown transaction occurs for purposes of computing earnings per unit under the two-class method are also required. The Partnership is required to adopt ASU 2015-06 for periods beginning after December 15, 2015, including interim periods, and the guidance is to be applied retrospectively, with early adoption permitted. The Partnership is currently evaluating the impact the adoption of ASU 2015-06 will have on the Condensed Consolidated and Combined Financial Statements (unaudited) or Notes to Condensed Consolidated and Combined Financial Statements (unaudited). In April 2015, the FASB issued ASU 2015-05, Intangibles - Goodwill and Other-Internal-Use Software (Subtopic 350-40): Customer's Accounting for Fees Paid in a Cloud Computing Arrangement. ASU 2015-05 clarifies guidance on determining whether a cloud computing arrangement contains a software license that should be accounted for as internal-use software. The Partnership is required to adopt ASU 2015-05 for periods beginning after December 15, 2015, including interim periods, and the guidance is permitted to be applied either (1) prospectively to all agreements entered into or materially modified after the effective date or (2) retrospectively, with early adoption permitted. The Partnership is currently evaluating the impact the adoption of ASU 2015-05 will have on the Condensed Consolidated and Combined Financial Statements (unaudited) or Notes to Condensed Consolidated and Combined Financial Statements (unaudited). In April 2015, the FASB issued ASU 2015-03, Interest - Imputation of Interest (Subtopic 835-30): Simplifying the Presentation of Debt Issuance Costs. ASU 2015-03 changes the way entities present debt issuance costs in financial statements by presenting issuance costs on the balance sheet as a direct deduction from the related liability rather than as a deferred charge. Amortization of these costs will continue to be reported as interest expense. The Partnership is required to adopt ASU 2015-03 for periods beginning after December 15, 2015, including interim periods, and the guidance is to be applied retrospectively with early adoption permitted. The Partnership is currently evaluating the impact the adoption of ASU 2015-03 will have on the Condensed Consolidated and Combined Financial Statements (unaudited) or Notes to Condensed Consolidated and Combined Financial Statements (unaudited). In February 2015, the FASB issued ASU 2015-02, Consolidation (Topic 810): Amendments to the Consolidation Analysis . ASU 2015-02 amends consolidation guidance by including changes to the variable and voting interest models used by entities to evaluate whether an entity should be consolidated. The Partnership is required to adopt ASU 2015-02 for periods beginning after December 15, 2015, including interim periods, and the guidance is to be applied retrospectively or using a modified retrospective approach, with early adoption permitted. The Partnership is currently evaluating the impact the adoption of ASU 2015-02 will have on the Condensed Consolidated and Combined Financial Statements (unaudited) or Notes to Condensed Consolidated and Combined Financial Statements (unaudited).

Net Income Per Limited Partner

Net Income Per Limited Partner Unit	6 Months Ended
	Jun. 30, 2015
Net Income Per Limited Partner Unit [Abstract]
Net Income Per Limited Partner Unit	Net Income Per Limited Partner Unit Net income per unit applicable to common units and to subordinated units is computed by dividing the respective limited partners’ interest in net income by the weighted-average number of common units and subordinated units outstanding for the period. Because the Partnership has more than one class of participating securities, it uses the two-class method when calculating the net income per unit applicable to limited partners. The classes of participating securities include common units, subordinated units and incentive distribution rights. Basic and diluted net income per unit are the same because the Partnership does not have any potentially dilutive units outstanding for the periods presented. Pursuant to our cash distribution policy, within 60 days after the end of each quarter, we intend to distribute to the holders of common and subordinated units on a quarterly basis at least the minimum quarterly distribution of $0.1675 per unit, or $0.67 on an annualized basis, to the extent we have sufficient cash after establishment of cash reserves and payment of fees and expenses, including payments to our general partner and its affiliates. On July 30, 2015, the board of directors of MLP GP, the Partnership's general partner, declared a quarterly cash distribution for the period April 1, 2015, through June 30, 2015 , of $0.1675 per unit, or $16.9 million in total. This distribution is payable on August 20, 2015 , to unitholders of record as of August 13, 2015 . The calculation of net income per unit is as follows: Three Months Ended Six Months Ended June 30, (1) (in millions) 2015 2015 Net income attributable to limited partners $ 16.3 $ 29.6 Less: Limited partners' distribution on common units 9.0 13.9 Limited partners' distribution on subordinated units 7.9 12.2 Distribution on incentive distribution rights — — Net income (less than) in excess of distribution $ (0.6 ) $ 3.5 (1) Net income attributable to limited partners and in excess of distribution is for the period subsequent to the IPO. Three Months Ended June 30, 2015 (in millions, except per unit data) Limited Partners' Common Units Limited Partners' Subordinated Units Incentive Distribution Rights Total Net income attributable to limited partners Distribution $ 9.0 $ 7.9 $ — $ 16.9 Net income less than distribution — (0.6 ) — (0.6 ) Net income attributable to limited partners $ 9.0 $ 7.3 $ — $ 16.3 Weighted average limited partner units outstanding Basic and diluted 53.8 46.8 — 100.6 Net income attributable to partners' ownership interest subsequent to IPO per limited partner unit Basic and diluted $ 0.17 $ 0.16 $ — $ 0.16 Six Months Ended June 30, 2015 (in millions, except per unit data) Limited Partners' Common Units Limited Partners' Subordinated Units Incentive Distribution Rights Total Net income attributable to limited partners subsequent to IPO Distribution $ 13.9 $ 12.2 $ — $ 26.1 Net income subsequent to IPO in excess of distribution 2.2 1.3 $ — 3.5 Net income attributable to limited partners subsequent to IPO $ 16.1 $ 13.5 $ — $ 29.6 Weighted average limited partner units outstanding Basic and diluted 53.8 46.8 — 100.6 Net income attributable to partners' ownership interest subsequent to IPO per limited partner unit Basic and diluted $ 0.30 $ 0.29 $ — $ 0.29

Transactions With Affiliates

Transactions With Affiliates	6 Months Ended
	Jun. 30, 2015
Related Party Transactions [Abstract]
Transactions With Affiliates	Transactions with Affiliates In the normal course of business, the Partnership engages in transactions with subsidiaries of NiSource, which prior to the Separation, were deemed to be affiliates of the Partnership. These affiliate transactions are summarized in the tables below: Statement of Operations. Three Months Ended Six Months Ended June 30, (in millions) 2015 2014 2015 2014 Predecessor Predecessor Transportation revenues $ 18.4 $ 18.9 $ 47.1 $ 47.5 Storage revenues 12.9 13.2 26.2 26.9 Other revenues 0.1 0.1 0.2 0.2 Operation and maintenance expense 38.6 29.5 74.7 57.8 Interest expense 6.3 12.6 17.7 24.7 Interest income 2.3 0.1 3.3 0.2 Balance Sheet. (in millions) June 30, December 31, 2014 Predecessor Accounts receivable $ 656.7 $ 153.8 Current portion of long-term debt — 115.9 Short-term borrowings 67.1 247.3 Accounts payable 41.5 49.9 Long-term debt 630.9 1,472.8 Transportation, Storage and Other Revenues . The Partnership provides natural gas transportation, storage and other services to subsidiaries of NiSource. Prior to the IPO, the Predecessor provided similar services to subsidiaries of NiSource. Operation and Maintenance Expense . The Partnership receives executive, financial, legal, information technology and other administrative and general services from NiSource Corporate Services and Columbia Pipeline Group Services Company. Prior to the IPO, the Predecessor received similar services from NiSource Corporate Services. Expenses incurred as a result of these services consist of employee compensation and benefits, outside services and other expenses. The expenses are charged directly or allocated using various allocation methodologies based on a combination of gross fixed assets, total operating expense, number of employees and other measures. Management believes the allocation methodologies are reasonable. However, these allocations and estimates may not represent the amounts that would have been incurred had the services been provided by an outside entity. Interest Expense and Income . The Partnership and Predecessor were charged interest for long-term debt of $7.5 million and $13.9 million for the three months ended June 30, 2015 and 2014 , respectively, offset by associated AFUDC of $1.4 million and $2.0 million for the three months ended June 30, 2015 and 2014 , respectively. The Partnership and Predecessor were charged interest for long-term debt of $19.7 million and $26.1 million for the six months ended June 30, 2015 and 2014 , respectively, offset by associated AFUDC of $2.4 million and $3.2 million for the six months ended June 30, 2015 and 2014 , respectively. Columbia OpCo and its subsidiaries entered into an intercompany money pool agreement with NiSource Finance, which became effective on the date of the IPO. The money pool is available for Columbia OpCo and its subsidiaries' general purposes, including capital expenditures and working capital. This intercompany money pool agreement is discussed in connection with Short-term Borrowings below. Prior to the IPO, the subsidiaries of the Predecessor participated in a similar money pool agreement with NiSource Finance. NiSource Corporate Services administers the money pools. The cash accounts maintained by the subsidiaries of Columbia OpCo and the Predecessor were, prior to the Separation, swept into a NiSource corporate account on a daily basis, creating an affiliated receivable or decreasing an affiliated payable, as appropriate, between NiSource and the subsidiary. The amount of interest expense and income for short-term borrowings is determined by the net position of each subsidiary in the money pool. The money pool weighted-average interest rate at June 30, 2015 and 2014 was 1.21% and 0.64% , respectively. For the three months ended June 30, 2015 and 2014 , the interest expense for short-term borrowings charged was $0.2 million and $0.7 million , respectively. For the six months ended June 30, 2015 and 2014 , the interest expense for short-term borrowings charged was $0.4 million and $1.8 million , respectively. Accounts Receivable . The Partnership includes in accounts receivable amounts due from the money pool discussed above of $643.2 million at June 30, 2015 for subsidiaries of Columbia OpCo in a net deposit position and the Partnership. The Predecessor includes in accounts receivable amounts due from the money pool discussed above of $ 125.0 million at December 31, 2014 for subsidiaries in a net deposit position. Also included in the balance at June 30, 2015 and December 31, 2014 are amounts due from subsidiaries of NiSource for transportation and storage services of $13.4 million and $28.8 million , respectively. Net cash flows related to the money pool receivables are included as Investing Activities on the Condensed Statements of Consolidated and Combined Cash Flows (unaudited). All other affiliated receivables are included as Operating Activities. Short-term Borrowings . In connection with the closing of the IPO, the subsidiaries of Columbia OpCo entered into an intercompany money pool agreement with NiSource Finance with $750.0 million of reserved borrowing capacity. Following the Separation, the agreement is now with CPG. In furtherance of the money pool agreement, CPG entered into a $1,500.0 million revolving credit agreement on December 5, 2014. The CPG revolving credit agreement became effective at the completion of the Separation. Each of CEG, OpCo GP and Columbia OpCo is a guarantor of CPG's revolving credit facility. As a guarantor and restricted subsidiary, Columbia OpCo is subject to various customary covenants and restrictive provisions which, among other things, limit CPG’s and its restricted subsidiaries’ ability to incur additional indebtedness, guarantees and/or liens; consolidate, merge or transfer all or substantially all of their assets; make certain investments or restricted payments; modify certain material agreements; engage in certain types of transactions with affiliates; dispose of assets; and prepay certain indebtedness; each of which is subject to customary and usual exceptions and baskets, including an exception to the limitation on restricted payments for distributions of available cash, as permitted by their organizational documents. The restricted payment provision does not prohibit CPG of any of its restricted subsidiaries from making distributions in accordance with their respective organizational documents unless there has been an event of default (as defined in the revolving credit agreement), and neither CPG nor any of its restricted subsidiaries has any restrictions on its ability to make distributions under its organizational documents. Under Columbia OpCo's partnership agreement, it is required to distribute all of its available cash each quarter, less the amounts of cash reserves that OpCo GP determines are necessary or appropriate in its reasonable discretion to provide for the proper conduct of Columbia OpCo's business. In addition, subject to Delaware law, the board of CPG may similarly determine whether to declare dividends at CPG without restriction under its revolving credit agreement. At June 30, 2015 , neither CPG nor its subsidiaries had any restricted assets. If Columbia OpCo and the other loan parties fail to perform their obligations under these and other covenants, it could adversely affect Columbia OpCo’s ability to finance future business opportunities and make cash distributions to CPPL. CPG’s revolving credit facility also contains customary events of default, including cross default provisions that apply to any other indebtedness CPG may have with an outstanding principal amount in excess of $50.0 million . If a default occurred, the relevant lenders could elect to declare the debt, together with accrued interest and other fees, to be immediately due and payable and proceed against Columbia OpCo as a guarantor. The balance of Short-term Borrowings at June 30, 2015 and December 31, 2014 of $67.1 million and $247.3 million , respectively, includes those subsidiaries of Columbia OpCo and those subsidiaries of the Predecessor in a net borrower position of the NiSource Finance money pool discussed above. Net cash flows related to Short-term Borrowings are included as Financing Activities on the Condensed Statements of Consolidated and Combined Cash Flows (unaudited). Accounts Payable . The affiliated accounts payable balance primarily includes amounts due for services received from NiSource Corporate Services and interest payable to NiSource Finance. Long-term Debt . In May 2015, the Partnership's outstanding intercompany debt transferred from NiSource Finance to CPG. The Partnership's long-term financing requirements are satisfied through borrowings from CPG. Details of the long-term debt balance are summarized in the table below: Origination Date Interest Rate Maturity Date June 30, 2015 December 31, 2014 (in millions) Predecessor November 28, 2005 (1) 5.41 % November 30, 2015 $ — $ 115.9 November 28, 2005 5.45 % November 28, 2016 — 45.3 November 28, 2005 5.92 % November 28, 2025 — 133.5 November 28, 2012 4.63 % November 28, 2032 — 45.0 November 28, 2012 4.94 % November 30, 2037 — 95.0 December 19, 2012 5.16 % December 21, 2037 — 55.0 November 28, 2012 5.26 % November 28, 2042 — 170.0 December 19, 2012 5.49 % December 18, 2042 — 95.0 December 9, 2013 (2) 4.75 % December 31, 2016 630.9 834.0 Total Long-term Debt $ 630.9 $ 1,588.7 (1) The debt balance for the note originating on November 28, 2005 and maturing on November 30, 2015 is included in "Current portion of long-term debt-affiliated" on the Condensed Combined Balance Sheet as of December 31, 2014. (2) The Partnership may borrow at any time from the origination date to the maturity date not to exceed $2.6 billion . The note carries a variable interest rate of prime plus 150 basis points. All funds borrowed on the note are due December 31, 2016 . Dividends . During the six months ended June 30, 2015 , Columbia OpCo distributed $500.0 million to CEG as a reimbursement of preformation capital expenditures with respect to the assets contributed to Columbia OpCo. The Partnership paid no dividends to CEG in the six months ended June 30, 2014 . There were no restrictions on the payment by the Partnership of dividends to CEG.

Short-Term Borrowings

Short-Term Borrowings	6 Months Ended
	Jun. 30, 2015
Short-term Debt [Abstract]
Short-Term Borrowings	Short-Term Borrowings On December 5, 2014, the Partnership entered into a $500.0 million senior revolving credit facility, of which $50.0 million in letters of credit is available. The revolving credit facility became effective at the closing of our IPO. The credit facility is available for general partnership purposes, including working capital and capital expenditures, including the funding of capital calls. Our obligations under the revolving credit facility are unsecured. The loans thereunder bear interest at our option at either (i) the greatest of (a) the federal funds effective rate plus 0.500 percent , (b) the reference prime rate of Wells Fargo Bank, National Association or (c) the Eurodollar rate which is based on the London Interbank Offered Rate (“LIBOR”), plus 1.000 percent , each of which is subject to a margin that varies from 0.000 percent to 0.650 percent per annum, according to the credit rating of CPG, or (ii) the Eurodollar rate plus a margin that varies from 1.000 percent to 1.650 percent per annum, according to the credit rating of CPG. The revolving credit facility is subject to a facility fee that varies from 0.125 percent to 0.350 percent per annum, according to the credit rating of CPG. The revolving indebtedness under the credit facility ranks equally with all our outstanding unsecured and unsubordinated debt. CPG, CEG, OpCo GP and Columbia OpCo each fully guarantee the credit facility. Our revolving credit facility contains various covenants and restrictive provisions which, among other things, limit our ability and our restricted subsidiaries’ ability to incur additional indebtedness, guarantees and/or liens; consolidate, merge or transfer all or substantially all of our assets; make certain investments or restricted payments; modify certain material agreements; engage in certain types of transactions with affiliates; dispose of assets; and prepay certain indebtedness; each of which is subject to customary and usual exceptions and baskets, including an exception to the limitation on restricted payments for distributions of available cash, as permitted by our organizational documents. The restricted payment provision does not prohibit us or any of our restricted subsidiaries from making distributions in accordance with our respective organizational documents unless there has been an event of default (as defined in our revolving credit agreement), and neither us nor any of our restricted subsidiaries has any restrictions on our ability to make distributions under our organization agreements. In particular, in accordance with our partnership agreement, the general partner has adopted a policy that we will make quarterly cash distributions in amounts equal to at least the minimum quarterly distribution of $0.1675 on each common and subordinated unit. However, the determination to make any distributions of cash is subject to the discretion of the general partner. At June 30, 2015 , neither us nor our consolidated subsidiaries had any restricted assets. If we fail to perform our obligations under these and other covenants, the revolving credit commitment could be terminated and any outstanding borrowings, together with accrued interest, under the revolving credit facility could be declared immediately due and payable. Our revolving credit facility also contains customary events of default, including cross default provisions that apply to any other indebtedness we may have with an outstanding principal amount in excess of $50.0 million . The revolving credit facility also contains certain financial covenants that require us to maintain a consolidated total leverage ratio that does not exceed (i) 5.75 to 1.00 for the period of four consecutive fiscal quarters (“test period”) ending December 31, 2015, (ii) 5.50 to 1.00 for any test period ending after December 31, 2015 and on or before December 31, 2017, and (iii) 5.00 to 1.00 for any test period ending after December 31, 2017, provided that after December 31, 2017 and during a Specified Acquisition Period (as defined in the revolving credit facility), the leverage ratio shall not exceed 5.50 to 1.00 . As of June 30, 2015 , the Partnership had $20.0 million in outstanding borrowings and issued no letters of credit under the revolving credit facility.

Gain On Sale Of Assets

Gain On Sale Of Assets	6 Months Ended
	Jun. 30, 2015
Gain On Sale of Assets [Abstract]
Gain On Sale Of Assets	Gain on Sale of Assets The Partnership recognizes gains on conveyances of mineral rights positions into earnings as any obligation associated with conveyance is satisfied. For the three months ended June 30, 2015 and 2014 , gains on conveyances of $8.3 million and $0.3 million were recorded in earnings, respectively. For the six months ended June 30, 2015 and 2014 , gains on conveyances of $13.6 million and $ 17.8 million were recorded in earnings, respectively. As of June 30, 2015 and December 31, 2014 , deferred gains of approximately $10.9 million and $19.6 million , respectively, were deferred pending performance of future obligations and recorded within "Deferred revenue," on the Condensed Consolidated and Combined Balance Sheets (unaudited).

Goodwill

Goodwill	6 Months Ended
	Jun. 30, 2015
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill	Goodwill The Partnership tests its goodwill for impairment annually as of May 1 unless indicators, events, or circumstances would require an immediate review. Goodwill is tested for impairment using financial information at the reporting unit level, referred to as the Columbia Gas Transmission Operations reporting unit, which is consistent with the level of discrete financial information reviewed by operating segment management. The Columbia Gas Transmission Operations reporting unit includes the following entities: Columbia Gas Transmission (including its equity method investment in the Millennium Pipeline joint venture), Columbia Gulf and the equity method investment in Hardy Storage, all of which have been designated as components and aggregated based on the regulated nature of their operations and similar economic characteristics (e.g., the offering of FERC-regulated pipeline transportation and storage services to LDCs, municipal utilities, direct industrial users, electric power generators and marketers). All of the goodwill relates to NiSource’s acquisition of CEG in 2000. The Partnership’s goodwill assets at June 30, 2015 were $1,975.5 million . The Partnership completed a quantitative (“step 1”) fair value measurement of the reporting unit during the May 1, 2012 goodwill test. The test indicated that the fair value of the reporting unit substantially exceeded the carrying value, indicating that no impairment existed. GAAP allows entities testing goodwill for impairment the option of performing a qualitative (“step 0”) assessment before calculating the fair value of a reporting unit for the goodwill impairment test. If a step 0 assessment is performed, an entity is no longer required to calculate the fair value of a reporting unit unless the entity determines that, based on that assessment, it is more likely than not that its fair value is less than its carrying amount. The Partnership applied the qualitative step 0 analysis to its reporting unit for the annual impairment test performed as of May 1, 2015 . For the current year test, the Partnership assessed various assumptions, events and circumstances that would have affected the estimated fair value of the reporting unit as compared to its base line May 1, 2012 step 1 fair value measurement. The results of this assessment indicated that it is not more likely than not that its reporting unit fair value is less than the reporting unit carrying value. The Partnership considered whether there were any events or changes in circumstances subsequent to the annual test that would reduce the fair value of the reporting unit below its carrying amount and necessitate another goodwill impairment test. No such indicators were noted that would require a subsequent goodwill impairment testing during the second quarter of 2015 .

Asset Retirement Obligations

Asset Retirement Obligations	6 Months Ended
	Jun. 30, 2015
Asset Retirement Obligation [Abstract]
Asset Retirement Obligations	Asset Retirement Obligations Changes in the Partnership’s liability for asset retirement obligations for the six months ended June 30, 2015 and 2014 are presented in the table below: (in millions) 2015 2014 Predecessor Balance as of January 1, $ 23.2 $ 26.3 Noncontributed net parent investment adjustments (1) (0.4 ) — Accretion expense 0.6 0.8 Additions 0.4 2.0 Settlements — — Change in estimated cash flows — (0.2 ) Balance as of June 30, $ 23.8 $ 28.9 (1) Reflects the removal of amounts related to Crossroads Pipeline Company, which was included in the Predecessor but was not contributed to the Partnership. The asset retirement obligations above relate to the modernization program of pipelines and transmission facilities, the retiring of offshore facilities, polychlorinated biphenyl ("PCB") remediation and asbestos removal at several compressor and measuring stations. The Partnership recognizes that there are obligations to incur significant costs to retire wells associated with gas storage operations; however, the lives of these wells are indeterminable until management establishes plans for closure.

Regulatory Matters

Regulatory Matters	6 Months Ended
	Jun. 30, 2015
Regulatory Assets and Liabilities Disclosure [Abstract]
Regulatory Matters	Regulatory Matters Columbia Gas Transmission Customer Settlement. In January 2015, Columbia Gas Transmission commenced the third year of the Columbia Gas Transmission long-term system modernization program. Columbia Gas Transmission expects to invest approximately $300 million in modernization investments during the year. Recovery of approximately $320 million of investments made in 2014 began on February 1, 2015. Cost Recovery Trackers and other similar mechanisms. A significant portion of the transmission and storage regulated companies' revenue is related to the recovery of their operating costs, the review and recovery of which occurs via standard regulatory proceedings with the FERC under section 4 of the Natural Gas Act. However, certain operating costs of the Columbia OpCo regulated transmission and storage companies are significant and recurring in nature, such as fuel for compression and lost and unaccounted for gas. The FERC allows for the recovery of such costs via cost tracking mechanisms. These tracking mechanisms allow the transmission and storage companies' rates to fluctuate in response to changes in certain operating costs or conditions as they occur to facilitate the timely recovery of its costs incurred. The tracking mechanisms involve a rate adjustment that is filed at a predetermined frequency, typically annually, with the FERC and is subject to regulatory review before new rates go into effect. Other such costs under regulatory tracking mechanisms include upstream pipeline transmission, electric compression, operational purchases and sales of natural gas, and the revenue requirement for capital investments made under Columbia Gas Transmission's long-term plan to modernize its interstate transmission system as discussed above.

Equity Method Investments

Equity Method Investments	6 Months Ended
	Jun. 30, 2015
Equity Method Investments [Abstract]
Equity Method Investments	Equity Method Investments Certain investments of the Partnership are accounted for under the equity method of accounting. Income and losses from Millennium Pipeline, Hardy Storage and Pennant are reflected in “Equity Earnings in Unconsolidated Affiliates” on the Condensed Statements of Consolidated and Combined Operations (unaudited). These investments are integral to the Partnership’s business. Contributions are made to these equity investees to fund the Partnership’s share of capital projects. Columbia Gas Transmission made no contributions to Millennium Pipeline for the three months ended June 30, 2015 and 2014 . Millennium Pipeline distributed $7.6 million and $4.8 million of earnings to Columbia Gas Transmission during the three months ended June 30, 2015 and 2014 , respectively. Columbia Gas Transmission made no contributions to Millennium Pipeline for the six months ended June 30, 2015 and contributed $2.6 million for the six months ended June 30, 2014 . Millennium Pipeline distributed $24.2 million and $11.9 million of earnings to Columbia Gas Transmission during the six months ended June 30, 2015 and 2014 , respectively. No contributions were made to Hardy Storage during the three months ended June 30, 2015 and 2014 . Hardy Storage distributed $0.5 million of earnings to NiSource during each of the three months ended June 30, 2015 and 2014 , respectively. No contributions were made to Hardy Storage during the six months ended June 30, 2015 and 2014 . Hardy Storage distributed $1.0 million of earnings to NiSource during each of the six months ended June 30, 2015 and 2014 , respectively. No contributions were made to Pennant for the three months ended June 30, 2015 and contributions of $23.8 million were made for the three months ended June 30, 2014 . Pennant distributed $1.5 million of earnings and returned $0.9 million of capital to Columbia Midstream during the three months ended June 30, 2015 . No distributions were received from Pennant during the three months ended June 30, 2014 . No contributions were made to Pennant for the six months ended June 30, 2015 and contributions of $52.2 million were made for the six months ended June 30, 2014 . Pennant distributed $2.7 million of earnings and returned $2.2 million of capital to Columbia Midstream during the six months ended June 30, 2015 . No distributions were received from Pennant during the six months ended June 30, 2014 .

Income Taxes

Income Taxes	6 Months Ended
	Jun. 30, 2015
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The Partnership is a limited partnership and is treated as a partnership for U.S. federal income tax purposes and, therefore, is not liable for entity-level federal income taxes. The Predecessor’s operating results were included in NiSource’s consolidated U.S. federal income tax return and in consolidated, combined or stand-alone state income tax returns. Amounts presented in the combined financial statements prior to the IPO relate to income taxes that have been determined on a separate tax return basis, and the Predecessor’s contribution to NiSource’s net operating losses and tax credits have been included in the Predecessor’s financial statements. The Partnership’s interim effective tax rates reflect the estimated annual effective tax rates for 2015 and 2014 , adjusted for tax expense associated with certain discrete items. The effective tax rates for the three months ended June 30, 2015 and 2014 were zero and 36.7% , respectively. The effective tax rates for the six months ended June 30, 2015 and 2014 were 9.0% and 37.2% , respectively. The effective tax rate for 2014 differs from the Federal tax rate of 35% primarily due to the effects of tax credits, state income taxes, utility rate making, and other permanent book-to-tax differences. The effective tax rate for 2015 differs from the Federal tax rate of 35% primarily due to the effects of tax credits, state income taxes, utility rate making, other permanent book-to-tax differences, and post-IPO income that is not subject to income tax at the partnership level.

Pension And Other Postretiremen

Pension And Other Postretirement Benefits	6 Months Ended
	Jun. 30, 2015
Pension and Other Postretirement Benefit Expense [Abstract]
Pension And Other Postretirement Benefits	Pension and Other Postretirement Benefits NiSource provides defined contribution plans and noncontributory defined benefit retirement plans that cover employees of subsidiaries of Columbia OpCo. Benefits under the defined benefit retirement plans reflect the employees’ compensation, years of service and age at retirement. Additionally, NiSource provides health care and life insurance benefits for certain retired employees of subsidiaries of Columbia OpCo. The majority of employees may become eligible for these benefits if they reach retirement age while working for subsidiaries of Columbia OpCo. The expected cost of such benefits is accrued during the employees’ years of service. Current rates charged to customers of subsidiaries of Columbia OpCo include postretirement benefit costs. Cash contributions are remitted to grantor trusts. Subsidiaries of Columbia OpCo are participants in the consolidated NiSource defined benefit retirement plans (the Plans) and, therefore, subsidiaries of Columbia OpCo are allocated a ratable portion of NiSource’s grantor trusts for the Plans in which its employees and retirees participate. As a result, the Partnership follows multiple employer accounting under the provisions of GAAP. For the six months ended June 30, 2015 , subsidiaries of Columbia OpCo have made no contributions to its pension plans and contributed $3.0 million to its other postretirement benefit plans. The following table provides the components of the subsidiaries of Columbia OpCo's allocation of net periodic benefits cost for the three and six months ended June 30, 2015 and 2014 : Pension Benefits Other Postretirement Benefits Three Months Ended June 30, (in millions) 2015 2014 2015 2014 Predecessor Predecessor Components of Net Periodic Benefit Cost (Income) Service cost $ 1.3 $ 1.2 $ 0.3 $ 0.2 Interest cost 3.0 3.5 1.0 1.2 Expected return on assets (6.1 ) (6.0 ) (4.3 ) (4.0 ) Amortization of prior service credit (0.2 ) (0.3 ) — — Recognized actuarial loss 2.1 1.7 — — Total Net Periodic Benefit Cost (Income) $ 0.1 $ 0.1 $ (3.0 ) $ (2.6 ) Pension Benefits Other Postretirement Benefits Six Months Ended June 30, (in millions) 2015 2014 2015 2014 Predecessor Predecessor Components of Net Periodic Benefit Cost (Income) Service cost $ 2.6 $ 2.4 $ 0.6 $ 0.5 Interest cost 6.1 6.9 2.0 2.4 Expected return on assets (12.2 ) (11.9 ) (8.6 ) (8.1 ) Amortization of prior service credit (0.4 ) (0.5 ) — — Recognized actuarial loss 4.1 3.3 — — Total Net Periodic Benefit Cost (Income) $ 0.2 $ 0.2 $ (6.0 ) $ (5.2 )

Fair Value

Fair Value	6 Months Ended
	Jun. 30, 2015
Fair Value Disclosures [Abstract]
Fair Value	Fair Value The Partnership has certain financial instruments that are not measured at fair value on a recurring basis but nevertheless are recorded at amounts that approximate fair value due to their liquid or short-term nature, including cash and cash equivalents, customer deposits, short-term borrowings and short-term borrowings-affiliated. The Partnership's long-term debt-affiliated is recorded at historical amounts. The following methods and assumptions were used to estimate the fair value of each class of financial instruments for which it is practicable to estimate fair value. Long-term debt-affiliated. The fair values of these securities are estimated based on the quoted market prices for similar issues or on the rates offered for securities of the same remaining maturities. These fair value measurements are classified as Level 2 within the fair value hierarchy. For the six months ended June 30, 2015 and for the year ended December 31, 2014 , there were no changes in the method or significant assumptions used to estimate the fair value of the financial instruments. The carrying amount and estimated fair values of financial instruments were as follows: (in millions) Carrying Amount as of June 30, 2015 Estimated Fair Value as of June 30, 2015 Carrying Amount as of Dec. 31, 2014 Estimated Fair Value as of Dec. 31, 2014 Predecessor Current portion of long-term debt-affiliated $ — $ — $ 115.9 $ 120.0 Long-term debt-affiliated 630.9 630.9 1,472.8 1,550.4

Other Commitments And Contingen

Other Commitments And Contingencies	6 Months Ended
	Jun. 30, 2015
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Other Commitments and Contingencies A. Guarantees and Indemnities. In the normal course of its business, the Partnership and certain subsidiaries enter into various agreements providing financial or performance assurance to third parties on behalf of the parent or certain subsidiaries. Such agreements include guarantees and stand-by letters of credit. These agreements are entered into primarily to support or enhance the creditworthiness otherwise attributed to the parent or a subsidiary on a stand-alone basis, thereby facilitating the extension of sufficient credit to accomplish the parent or the subsidiaries' intended commercial purposes. The total guarantees and indemnities in existence at June 30, 2015 and the years in which they expire were: (in millions) Total 2015 2016 2017 2018 2019 After Guarantees of debt $ 2,750.0 $ — $ — $ — $ 500.0 $ — $ 2,250.0 Lines of credit 20.0 20.0 — — — — — Total commercial commitments $ 2,770.0 $ 20.0 $ — $ — $ 500.0 $ — $ 2,250.0 Guarantees of Debt. Certain of CPG's subsidiaries, including CEG, OpCo GP and Columbia OpCo have guaranteed payment of $2,750.0 million in aggregated principal amount of CPG's senior notes. Each guarantee of CPG's obligations is required to comply with covenants under the debt indenture and in the event of default the guarantors would be obligated to pay the debt's principal and related interest. The Partnership does not anticipate its subsidiaries will have any difficulty maintaining compliance. Lines and Letters of Credit. The Partnership maintains a $500.0 million senior revolving credit facility, of which $50.0 million is available for issuance of letters of credit. The purpose of the facility is to provide cash for general partnership purposes, including working capital, capital expenditures, and the funding of capital calls. As of June 30, 2015 , the Partnership had $20.0 million in outstanding borrowings and no letters of credit under the revolving credit facility. B. Other Legal Proceedings. In the normal course of its business, the Partnership has been named as a defendant in various legal proceedings. In the opinion of management, the ultimate disposition of these currently asserted claims will not have a material impact on the Partnership’s consolidated and combined financial statements. C. Environmental Matters. The Partnership's operations are subject to environmental statutes and regulations related to air quality, water quality, hazardous waste and solid waste. The Partnership believes that it is in substantial compliance with those environmental regulations currently applicable to its operations and believes that it has all necessary permits to conduct its operations. It is the Partnership's continued intent to address environmental issues in cooperation with regulatory authorities in such a manner as to achieve mutually acceptable compliance plans. However, there can be no assurance that fines and penalties will not be incurred. The Partnership records accruals to cover environmental remediation at various sites. The current portion of this accrual is included in “Legal and environmental” in the Condensed Consolidated and Combined Balance Sheets (unaudited). The noncurrent portion is included in “Other noncurrent liabilities” in the Condensed Consolidated and Combined Balance Sheets (unaudited). National Ambient Air Quality Standards. The CAA requires the EPA to set NAAQS for particulate matter and five other pollutants considered harmful to public health and the environment. Periodically, the EPA imposes new or modifies existing NAAQS. States that contain areas that do not meet the new or revised standards must take steps to maintain or achieve compliance with the standards. These steps could include additional pollution controls on boilers, engines, turbines, and other facilities owned by the Partnership. The following NAAQS were recently added or modified: Ozone: On November 25, 2014, the EPA proposed to lower the 8-hour ozone standard from 75 ppb to within a range of 65-70 ppb. If the standard is finalized and the EPA proceeds with designations, areas where the Partnership operates currently designated as attainment may be re-classified as non-attainment. The Partnership will continue to monitor this matter and cannot estimate its impact at this time. Nitrogen Dioxide (NO2): The EPA revised the NO2 NAAQS by adding a one-hour standard while retaining the annual standard. The new standard could impact some Partnership combustion sources. The EPA designated all areas of the country as unclassifiable/attainment in January 2012. After the establishment of a new monitoring network and possible modeling implementation, areas will potentially be re-designated sometime in 2016. States with areas that do not meet the standard will be required to develop rules to bring areas into compliance within five years of designation. Additionally, under certain permitting circumstances, emissions from some existing Partnership combustion sources may need to be assessed and mitigated. The Partnership will continue to monitor this matter and cannot estimate the impact of these rules at this time.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Loss	6 Months Ended
	Jun. 30, 2015
Other Comprehensive Income (Loss), Tax [Abstract]
Accumulated Other Comprehensive Loss	Accumulated Other Comprehensive Loss The following tables display the components of Accumulated Other Comprehensive Loss for the three and six months ended June 30, 2015 and 2014 : Three Months Ended June 30, 2015 (in millions) Gains and Losses on Cash Flow Hedges Pension and OPEB Items Accumulated Other Comprehensive Loss Balance as of April 1, 2015 $ (4.1 ) $ (0.1 ) $ (4.2 ) Other comprehensive income before reclassifications — — — Amounts reclassified from accumulated other comprehensive income (2) 0.5 — 0.5 Net current-period other comprehensive (loss) income 0.5 — 0.5 Allocation of accumulated other comprehensive loss to noncontrolling interest 0.4 — 0.4 Balance as of June 30, 2015 $ (4.0 ) $ (0.1 ) $ (4.1 ) Six Months Ended June 30, 2015 (in millions) Gains and Losses on Cash Flow Hedges (1) Pension and OPEB Items (1) Accumulated Other Comprehensive Loss (1) Balance as of January 1, 2015 $ (16.6 ) $ (0.1 ) $ (16.7 ) Predecessor net tax liabilities not assumed by Columbia OpCo (3) (10.2 ) (0.1 ) (10.3 ) Other comprehensive income before reclassifications — — — Amounts reclassified from accumulated other comprehensive income (2) 0.6 — 0.6 Net current-period other comprehensive (loss) income 0.6 — 0.6 Allocation of accumulated other comprehensive loss to noncontrolling interest (22.2 ) (0.1 ) (22.3 ) Balance as of June 30, 2015 $ (4.0 ) $ (0.1 ) $ (4.1 ) (1) All amounts prior to the IPO are net of tax. Amounts in parentheses indicate debits. (2) Includes amounts allocated to noncontrolling interest. (3) Reflects the non-cash elimination of all historical current and deferred income taxes other than Tennessee state income taxes that will continue to be borne by the Partnership post-IPO. Three Months Ended June 30, 2014 (in millions) Gains and Losses on Cash Flow Hedges (1) Pension and OPEB Items (1) Accumulated (1) Predecessor Balance as of April 1, 2014 $ (17.3 ) $ (0.1 ) $ (17.4 ) Other comprehensive income before reclassifications — — — Amounts reclassified from accumulated other comprehensive income 0.2 — 0.2 Net current-period other comprehensive income 0.2 — 0.2 Balance as of June 30, 2014 $ (17.1 ) $ (0.1 ) $ (17.2 ) Six Months Ended June 30, 2014 (in millions) Gains and Losses on Cash Flow Hedges (1) Pension and OPEB Items (1) Accumulated Other Comprehensive Loss (1) Predecessor Balance as of January 1, 2014 $ (17.6 ) $ (0.1 ) $ (17.7 ) Other comprehensive income before reclassifications — — — Amounts reclassified from accumulated other comprehensive income 0.5 0.5 Net current-period other comprehensive income 0.5 — 0.5 Balance as of June 30, 2014 $ (17.1 ) $ (0.1 ) $ (17.2 ) (1) All amounts are net of tax. Amounts in parentheses indicated debits. Equity Investment Millennium Pipeline is an equity method investment and, therefore, Columbia OpCo is required to recognize a proportional share of Millennium Pipeline’s OCI. The remaining unrecognized loss at June 30, 2015 of $25.9 million , before tax, related to terminated interest rate swaps is being amortized over the period ending June 2025 into earnings using the effective interest method through interest expense as interest payments are made by Millennium Pipeline. The unrecognized loss of $25.9 million , before tax, and $16.6 million , after tax, at June 30, 2015 and December 31, 2014 , respectively, is included in gains and losses on cash flow hedges above.

Other, Net

Other, Net	6 Months Ended
	Jun. 30, 2015
Other Income and Expenses [Abstract]
Other, Net	Other, Net Three Months Ended June 30, Six Months Ended June 30, (in millions) 2015 2014 2015 2014 Predecessor Predecessor AFUDC Equity $ 4.9 $ 2.7 $ 8.4 $ 4.3 Miscellaneous — (0.1 ) 0.8 0.1 Total Other, net $ 4.9 $ 2.6 $ 9.2 $ 4.4

Supplemental Cash Flow Informat

Supplemental Cash Flow Information	6 Months Ended
	Jun. 30, 2015
Supplemental Cash Flow Information [Abstract]
Supplemental Cash Flow Information	Supplemental Cash Flow Information The following table provides additional information regarding the Partnership’s Condensed Statements of Consolidated and Combined Cash Flows (unaudited) for the six months ended June 30, 2015 and 2014 : (in millions) 2015 2014 Predecessor Supplemental Disclosures of Cash Flow Information Non-cash transactions: Capital expenditures included in current liabilities (1) $ 184.5 $ 94.0 Schedule of interest and income taxes paid: Cash paid for interest, net of interest capitalized amounts $ 21.3 $ 27.7 Cash paid for income taxes — 35.7 (1) Capital expenditures included in current liabilities is comprised of "Accrued capital expenditures" and certain other amounts included within "Accounts payable" on the Condensed Consolidated and Combined Balance Sheet (unaudited).

Concentration Of Credit Risk

Concentration Of Credit Risk	6 Months Ended
	Jun. 30, 2015
Risks and Uncertainties [Abstract]
Concentration Risk Disclosure	Concentration of Credit Risk Columbia Gas of Ohio, an affiliated party, accounted for greater than 10% of total operating revenues for the three and six months ended June 30, 2015 and 2014 . The following tables provide the customer's operating revenues and percentage of total operating revenues for the three and six months ended June 30, 2015 and 2014 : Three Months Ended June 30, 2015 2014 (in millions) Total Operating Revenues Percentage of Total Operating Revenues Total Operating Revenues Percentage of Total Operating Revenues Predecessor Columbia Gas of Ohio (1) $ 36.2 11.5 % $ 36.0 10.5 % Six Months Ended June 30, 2015 2014 (in millions) Total Operating Revenues Percentage of Total Operating Revenues Total Operating Revenues Percentage of Total Operating Revenues Predecessor Columbia Gas of Ohio (1) $ 85.1 13.0 % $ 83.6 12.1 % (1) Represents the gross amount of revenue contracted for with Columbia Gas of Ohio and, therefore, subject to risk at the loss of this customer. Columbia Gas of Ohio has entered into certain capacity release arrangements with third parties which ultimately can decrease the net revenue amount we receive from Columbia Gas of Ohio in any given period. There was no other single customer that accounted for greater than 10% of operating revenues for the three and six months ended June 30, 2015 and 2014 . The loss of a significant portion of operating revenues from this customer would have a material adverse effect on the business of the Partnership.

Subsequent Events

Subsequent Events	6 Months Ended
	Jun. 30, 2015
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events Distribution. On July 30, 2015, the board of directors of MLP GP, the Partnership's general partner, declared a quarterly cash distribution for the period April 1, 2015 through June 30, 2015, of $0.1675 per unit, or $16.9 million . This distribution is payable on August 20, 2015 , to unitholders of record as of August 13, 2015 . Separation. On June 2, 2015 , NiSource's board of directors approved the distribution of all the shares of CPG to holders of NiSource common stock. In order to allow NiSource to effect the Separation, CPG requested, and the SEC declared effective, CPG's registration statement on Form 10 on June 2, 2015 . Effective July 1, 2015 , CPG authorized 317.6 million shares of common stock. On July 1, 2015 , NiSource distributed 317.6 million shares, one share of CPG common stock for every one share of NiSource common stock, held by NiSource shareholders of record as of the close of business on June 19, 2015 , the record date of the distribution. At the close of business on July 1, 2015 , CPG became an independent, publicly traded company as a result of the distribution. CPG's common stock began trading "regular-way" under the stock ticker symbol "CPGX" on the NYSE on July 2, 2015 . Gain on Conveyances. On December 29, 2014, CEVCO finalized an agreement with CNX Gas Company LLC, ("CNX"), a wholly owned subsidiary of CONSOL Energy, to lease approximately 20,000 acres of Utica Shale and Upper Devonian gas rights in Greene and Washington Counties in Pennsylvania and Marshall and Ohio Counties in West Virginia. Under the terms of the agreement, on July 1, 2015 CEVCO conveyed acres to CNX resulting in a bonus payment of $35.8 million . This amount will be recorded as a gain on conveyances in the third quarter of 2015.

Initial Public Offering (Tables

Initial Public Offering (Tables)	6 Months Ended
	Jun. 30, 2015
Equity [Abstract]
Change From Net Income Attributable to the Partnership and Transfers to Noncontrolling Interest	Three Months Ended Six Months Ended June 30, (in millions) 2015 2015 Net income attributable to the Partnership $ 16.3 $ 29.6 Decrease in partnership equity for the purchase of an additional 8.4 percent interest in Columbia OpCo — (424.4 ) Change from net income attributable to the Partnership and transfers to noncontrolling interest $ 16.3 $ (394.8 )

Net Income Per Limited Partne31

Net Income Per Limited Partner Unit (Tables)	6 Months Ended
	Jun. 30, 2015
Net Income Per Limited Partner Unit [Abstract]
Schedule of Undistributed Net Income	Three Months Ended Six Months Ended June 30, (1) (in millions) 2015 2015 Net income attributable to limited partners $ 16.3 $ 29.6 Less: Limited partners' distribution on common units 9.0 13.9 Limited partners' distribution on subordinated units 7.9 12.2 Distribution on incentive distribution rights — — Net income (less than) in excess of distribution $ (0.6 ) $ 3.5 (1) Net income attributable to limited partners and in excess of distribution is for the period subsequent to the IPO.
Schedule Of Net Income Per Limited Partner Unit	Three Months Ended June 30, 2015 (in millions, except per unit data) Limited Partners' Common Units Limited Partners' Subordinated Units Incentive Distribution Rights Total Net income attributable to limited partners Distribution $ 9.0 $ 7.9 $ — $ 16.9 Net income less than distribution — (0.6 ) — (0.6 ) Net income attributable to limited partners $ 9.0 $ 7.3 $ — $ 16.3 Weighted average limited partner units outstanding Basic and diluted 53.8 46.8 — 100.6 Net income attributable to partners' ownership interest subsequent to IPO per limited partner unit Basic and diluted $ 0.17 $ 0.16 $ — $ 0.16 Six Months Ended June 30, 2015 (in millions, except per unit data) Limited Partners' Common Units Limited Partners' Subordinated Units Incentive Distribution Rights Total Net income attributable to limited partners subsequent to IPO Distribution $ 13.9 $ 12.2 $ — $ 26.1 Net income subsequent to IPO in excess of distribution 2.2 1.3 $ — 3.5 Net income attributable to limited partners subsequent to IPO $ 16.1 $ 13.5 $ — $ 29.6 Weighted average limited partner units outstanding Basic and diluted 53.8 46.8 — 100.6 Net income attributable to partners' ownership interest subsequent to IPO per limited partner unit Basic and diluted $ 0.30 $ 0.29 $ — $ 0.29

Transactions With Affiliates (T

Transactions With Affiliates (Tables)	6 Months Ended
	Jun. 30, 2015
Related Party Transactions [Abstract]
Schedule of Transactions With Affiliates	Statement of Operations. Three Months Ended Six Months Ended June 30, (in millions) 2015 2014 2015 2014 Predecessor Predecessor Transportation revenues $ 18.4 $ 18.9 $ 47.1 $ 47.5 Storage revenues 12.9 13.2 26.2 26.9 Other revenues 0.1 0.1 0.2 0.2 Operation and maintenance expense 38.6 29.5 74.7 57.8 Interest expense 6.3 12.6 17.7 24.7 Interest income 2.3 0.1 3.3 0.2 Balance Sheet. (in millions) June 30, December 31, 2014 Predecessor Accounts receivable $ 656.7 $ 153.8 Current portion of long-term debt — 115.9 Short-term borrowings 67.1 247.3 Accounts payable 41.5 49.9 Long-term debt 630.9 1,472.8
Schedule of Related Party Transactions, Long-Term Debt	Origination Date Interest Rate Maturity Date June 30, 2015 December 31, 2014 (in millions) Predecessor November 28, 2005 (1) 5.41 % November 30, 2015 $ — $ 115.9 November 28, 2005 5.45 % November 28, 2016 — 45.3 November 28, 2005 5.92 % November 28, 2025 — 133.5 November 28, 2012 4.63 % November 28, 2032 — 45.0 November 28, 2012 4.94 % November 30, 2037 — 95.0 December 19, 2012 5.16 % December 21, 2037 — 55.0 November 28, 2012 5.26 % November 28, 2042 — 170.0 December 19, 2012 5.49 % December 18, 2042 — 95.0 December 9, 2013 (2) 4.75 % December 31, 2016 630.9 834.0 Total Long-term Debt $ 630.9 $ 1,588.7 (1) The debt balance for the note originating on November 28, 2005 and maturing on November 30, 2015 is included in "Current portion of long-term debt-affiliated" on the Condensed Combined Balance Sheet as of December 31, 2014. (2) The Partnership may borrow at any time from the origination date to the maturity date not to exceed $2.6 billion . The note carries a variable interest rate of prime plus 150 basis points. All funds borrowed on the note are due December 31, 2016 .

Asset Retirement Obligations (T

Asset Retirement Obligations (Tables)	6 Months Ended
	Jun. 30, 2015
Asset Retirement Obligation [Abstract]
Changes In Company's Liability For Asset Retirement Obligations	(in millions) 2015 2014 Predecessor Balance as of January 1, $ 23.2 $ 26.3 Noncontributed net parent investment adjustments (1) (0.4 ) — Accretion expense 0.6 0.8 Additions 0.4 2.0 Settlements — — Change in estimated cash flows — (0.2 ) Balance as of June 30, $ 23.8 $ 28.9 (1) Reflects the removal of amounts related to Crossroads Pipeline Company, which was included in the Predecessor but was not contributed to the Partnership.

Pension And Other Postretirem34

Pension And Other Postretirement Benefits (Tables)	6 Months Ended
	Jun. 30, 2015
Pension and Other Postretirement Benefit Expense [Abstract]
Components Of The Plans' Net Periodic Benefits Cost	Pension Benefits Other Postretirement Benefits Three Months Ended June 30, (in millions) 2015 2014 2015 2014 Predecessor Predecessor Components of Net Periodic Benefit Cost (Income) Service cost $ 1.3 $ 1.2 $ 0.3 $ 0.2 Interest cost 3.0 3.5 1.0 1.2 Expected return on assets (6.1 ) (6.0 ) (4.3 ) (4.0 ) Amortization of prior service credit (0.2 ) (0.3 ) — — Recognized actuarial loss 2.1 1.7 — — Total Net Periodic Benefit Cost (Income) $ 0.1 $ 0.1 $ (3.0 ) $ (2.6 ) Pension Benefits Other Postretirement Benefits Six Months Ended June 30, (in millions) 2015 2014 2015 2014 Predecessor Predecessor Components of Net Periodic Benefit Cost (Income) Service cost $ 2.6 $ 2.4 $ 0.6 $ 0.5 Interest cost 6.1 6.9 2.0 2.4 Expected return on assets (12.2 ) (11.9 ) (8.6 ) (8.1 ) Amortization of prior service credit (0.4 ) (0.5 ) — — Recognized actuarial loss 4.1 3.3 — — Total Net Periodic Benefit Cost (Income) $ 0.2 $ 0.2 $ (6.0 ) $ (5.2 )

Fair Value (Tables)

Fair Value (Tables)	6 Months Ended
	Jun. 30, 2015
Fair Value Disclosures [Abstract]
Carrying Amount And Estimated Fair Values Of Financial Instruments	(in millions) Carrying Amount as of June 30, 2015 Estimated Fair Value as of June 30, 2015 Carrying Amount as of Dec. 31, 2014 Estimated Fair Value as of Dec. 31, 2014 Predecessor Current portion of long-term debt-affiliated $ — $ — $ 115.9 $ 120.0 Long-term debt-affiliated 630.9 630.9 1,472.8 1,550.4

Other Commitments And Conting36

Other Commitments And Contingencies (Tables)	6 Months Ended
	Jun. 30, 2015
Commitments and Contingencies Disclosure [Abstract]
Schedule of Guarantee Obligations	The total guarantees and indemnities in existence at June 30, 2015 and the years in which they expire were: (in millions) Total 2015 2016 2017 2018 2019 After Guarantees of debt $ 2,750.0 $ — $ — $ — $ 500.0 $ — $ 2,250.0 Lines of credit 20.0 20.0 — — — — — Total commercial commitments $ 2,770.0 $ 20.0 $ — $ — $ 500.0 $ — $ 2,250.0

Accumulated Other Comprehensi37

Accumulated Other Comprehensive Loss (Tables)	6 Months Ended
	Jun. 30, 2015
Other Comprehensive Income (Loss), Tax [Abstract]
Components Of Accumulated Other Comprehensive Loss	Three Months Ended June 30, 2015 (in millions) Gains and Losses on Cash Flow Hedges Pension and OPEB Items Accumulated Other Comprehensive Loss Balance as of April 1, 2015 $ (4.1 ) $ (0.1 ) $ (4.2 ) Other comprehensive income before reclassifications — — — Amounts reclassified from accumulated other comprehensive income (2) 0.5 — 0.5 Net current-period other comprehensive (loss) income 0.5 — 0.5 Allocation of accumulated other comprehensive loss to noncontrolling interest 0.4 — 0.4 Balance as of June 30, 2015 $ (4.0 ) $ (0.1 ) $ (4.1 ) Six Months Ended June 30, 2015 (in millions) Gains and Losses on Cash Flow Hedges (1) Pension and OPEB Items (1) Accumulated Other Comprehensive Loss (1) Balance as of January 1, 2015 $ (16.6 ) $ (0.1 ) $ (16.7 ) Predecessor net tax liabilities not assumed by Columbia OpCo (3) (10.2 ) (0.1 ) (10.3 ) Other comprehensive income before reclassifications — — — Amounts reclassified from accumulated other comprehensive income (2) 0.6 — 0.6 Net current-period other comprehensive (loss) income 0.6 — 0.6 Allocation of accumulated other comprehensive loss to noncontrolling interest (22.2 ) (0.1 ) (22.3 ) Balance as of June 30, 2015 $ (4.0 ) $ (0.1 ) $ (4.1 ) (1) All amounts prior to the IPO are net of tax. Amounts in parentheses indicate debits. (2) Includes amounts allocated to noncontrolling interest. (3) Reflects the non-cash elimination of all historical current and deferred income taxes other than Tennessee state income taxes that will continue to be borne by the Partnership post-IPO. Three Months Ended June 30, 2014 (in millions) Gains and Losses on Cash Flow Hedges (1) Pension and OPEB Items (1) Accumulated (1) Predecessor Balance as of April 1, 2014 $ (17.3 ) $ (0.1 ) $ (17.4 ) Other comprehensive income before reclassifications — — — Amounts reclassified from accumulated other comprehensive income 0.2 — 0.2 Net current-period other comprehensive income 0.2 — 0.2 Balance as of June 30, 2014 $ (17.1 ) $ (0.1 ) $ (17.2 ) Six Months Ended June 30, 2014 (in millions) Gains and Losses on Cash Flow Hedges (1) Pension and OPEB Items (1) Accumulated Other Comprehensive Loss (1) Predecessor Balance as of January 1, 2014 $ (17.6 ) $ (0.1 ) $ (17.7 ) Other comprehensive income before reclassifications — — — Amounts reclassified from accumulated other comprehensive income 0.5 0.5 Net current-period other comprehensive income 0.5 — 0.5 Balance as of June 30, 2014 $ (17.1 ) $ (0.1 ) $ (17.2 ) (1) All amounts are net of tax. Amounts in parentheses indicated debits.

Other, Net (Tables)

Other, Net (Tables)	6 Months Ended
	Jun. 30, 2015
Other Income and Expenses [Abstract]
Schedule Of Other, Net [Table Text Block]	Three Months Ended June 30, Six Months Ended June 30, (in millions) 2015 2014 2015 2014 Predecessor Predecessor AFUDC Equity $ 4.9 $ 2.7 $ 8.4 $ 4.3 Miscellaneous — (0.1 ) 0.8 0.1 Total Other, net $ 4.9 $ 2.6 $ 9.2 $ 4.4

Supplemental Cash Flow Inform39

Supplemental Cash Flow Information (Tables)	6 Months Ended
	Jun. 30, 2015
Supplemental Cash Flow Information [Abstract]
Additional Information Regarding Condensed Statements Of Consolidated Cash Flows	(in millions) 2015 2014 Predecessor Supplemental Disclosures of Cash Flow Information Non-cash transactions: Capital expenditures included in current liabilities (1) $ 184.5 $ 94.0 Schedule of interest and income taxes paid: Cash paid for interest, net of interest capitalized amounts $ 21.3 $ 27.7 Cash paid for income taxes — 35.7 (1) Capital expenditures included in current liabilities is comprised of "Accrued capital expenditures" and certain other amounts included within "Accounts payable" on the Condensed Consolidated and Combined Balance Sheet (unaudited).

Concentration Of Credit Risk (T

Concentration Of Credit Risk (Tables)	6 Months Ended
	Jun. 30, 2015
Risks and Uncertainties [Abstract]
Schedule of Concentration Of Credit Risk	Three Months Ended June 30, 2015 2014 (in millions) Total Operating Revenues Percentage of Total Operating Revenues Total Operating Revenues Percentage of Total Operating Revenues Predecessor Columbia Gas of Ohio (1) $ 36.2 11.5 % $ 36.0 10.5 % Six Months Ended June 30, 2015 2014 (in millions) Total Operating Revenues Percentage of Total Operating Revenues Total Operating Revenues Percentage of Total Operating Revenues Predecessor Columbia Gas of Ohio (1) $ 85.1 13.0 % $ 83.6 12.1 % (1) Represents the gross amount of revenue contracted for with Columbia Gas of Ohio and, therefore, subject to risk at the loss of this customer. Columbia Gas of Ohio has entered into certain capacity release arrangements with third parties which ultimately can decrease the net revenue amount we receive from Columbia Gas of Ohio in any given period.

Basis of Accounting Presentat41

Basis of Accounting Presentation Basis of Accounting Presentation (Details) - 6 months ended Jun. 30, 2015	Total
Basis Of Accounting Presentation [Line Items]
Number Of Customers	3,800,000
Limited Liability Company (LLC) or Limited Partnership (LP), Members or Limited Partners, Ownership Interest	15.70%
Limited Liability Company or Limited Partnership, Managing Member or General Partner, Name	CPP GP LLC
Corporate Joint Venture [Member]
Basis Of Accounting Presentation [Line Items]
Limited Liability Company (LLC) or Limited Partnership (LP), Managing Member or General Partner, Ownership Interest	84.30%

Initial Public Offering (Narrat

Initial Public Offering (Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	5 Months Ended	6 Months Ended
	Feb. 11, 2015	Jun. 30, 2015	Jun. 30, 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	1,217.3
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
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
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] | 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]
Net proceeds from IPO		$ 1,168.4
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

Initial Public Offering (Schedu

Initial Public Offering (Schedule of Change From Net Income Attributable to the Partnership and Transfers to Noncontrolling Interest) (Details) - Jun. 30, 2015 - USD ($) $ in Millions		Total	Total		Total
Initial Public Offering [Line Items]
Net Income (Loss) Allocated to Limited Partners		$ 16.3			$ 29.6
Noncontrolling Interest, Increase from Subsidiary Equity Issuance	[1]		$ 0
Change from net income attributable to the Partnership and transfers to noncontrolling interest		16.3	(394.8)
Noncontrolling Interest [Member]
Initial Public Offering [Line Items]
Noncontrolling Interest, Increase from Subsidiary Equity Issuance		$ 0	$ (424.4)	[1]
[1]	Represents the purchase of an additional 8.4% limited partner interest in Columbia OpCo, recorded at the historical carrying value of Columbia OpCo’s net assets after giving effect to the $1,168.4 million equity contribution. This decreases common unitholders and subordinated unitholders equity by the same amount it increases noncontrolling interest because the MLP's purchase price for its additional 8.4% interest in Columbia OpCo exceeded book value.

Net Income Per Limited Partne44

Net Income Per Limited Partner Unit (Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions	Jul. 30, 2015	Jun. 30, 2015
Subsequent Event [Member]
Schedule Of Earnings Per Unit [Line Items]
Distribution Made to Limited Partner, Cash Distributions Declared	$ 16.9
Distribution Made to Limited Partner, Distributions Declared, Per Unit	$ 0.1675
Distribution Made to Limited Partner, Distribution Date	Aug. 20, 2015
Distribution Made to Limited Partner, Date of Record	Aug. 13, 2015
Minimum
Schedule Of Earnings Per Unit [Line Items]
Distribution Made to Limited Partner, Distributions Paid, Per Unit		$ 0.1675
Minimum | Annualized
Schedule Of Earnings Per Unit [Line Items]
Distribution Made to Limited Partner, Distributions Paid, Per Unit		$ 0.67

Net Income Per Limited Partne45

Net Income Per Limited Partner Unit (Schedule of Net Income In Excess Of Distribution) (Details) - Jun. 30, 2015 - USD ($) $ in Millions	Total	Total
Schedule of Undistributed Net Income [Line Items]
Net Income (Loss) Allocated to Limited Partners	$ 16.3	$ 29.6
Incentive Distribution, Distribution	0	0
Undistributed Earnings, Basic	(0.6)	3.5
Common Units [Member]
Schedule of Undistributed Net Income [Line Items]
Net Income (Loss) Allocated to Limited Partners	9	16.1
Distribution Made to Limited Partner, Cash Distributions Declared	9	13.9
Undistributed Earnings, Basic	0	2.2
Subordinated Units [Member]
Schedule of Undistributed Net Income [Line Items]
Net Income (Loss) Allocated to Limited Partners	7.3	13.5
Distribution Made to Limited Partner, Cash Distributions Declared	7.9	12.2
Undistributed Earnings, Basic	$ (0.6)	$ 1.3

Net Income Per Limited Partne46

Net Income Per Limited Partner Unit (Schedule of Net Income Per Limited Partner Unit) (Details) - Jun. 30, 2015 - USD ($) $ / shares in Units, shares in Millions, $ in Millions	Total	Total
Schedule Of Earnings Per Unit [Line Items]
Incentive Distribution, Distribution	$ 0	$ 0
Partners' Capital Account, Distributions	16.9	26.1
Undistributed Earnings, Basic	(0.6)	3.5
Net Income (Loss) Allocated to Limited Partners	$ 16.3	$ 29.6
Weighted Average Number of Shares Outstanding, Basic and Diluted	100.6	100.6
Net Income (Loss), Per Outstanding Limited Partnership and General Partnership Unit, Basic and Diluted, Net of Tax	$ 0.16	$ 0.29
Incentive Distribution Rights [Member]
Schedule Of Earnings Per Unit [Line Items]
Incentive Distribution, Distribution	$ 0	$ 0
Undistributed Earnings, Basic	0	0
Net Income (Loss) Allocated to Limited Partners	$ 0	$ 0
Weighted Average Number of Shares Outstanding, Basic and Diluted	0	0
Net Income (Loss), Per Outstanding Limited Partnership and General Partnership Unit, Basic and Diluted, Net of Tax	$ 0	$ 0
Subordinated Units [Member]
Schedule Of Earnings Per Unit [Line Items]
Distribution Made to Limited Partner, Cash Distributions Declared	$ 7.9	$ 12.2
Undistributed Earnings, Basic	(0.6)	1.3
Net Income (Loss) Allocated to Limited Partners	$ 7.3	$ 13.5
Weighted Average Number of Shares Outstanding, Basic and Diluted	46.8	46.8
Net Income (Loss), Per Outstanding Limited Partnership and General Partnership Unit, Basic and Diluted, Net of Tax	$ 0.16	$ 0.29
Common Units [Member]
Schedule Of Earnings Per Unit [Line Items]
Distribution Made to Limited Partner, Cash Distributions Declared	$ 9	$ 13.9
Undistributed Earnings, Basic	0	2.2
Net Income (Loss) Allocated to Limited Partners	$ 9	$ 16.1
Weighted Average Number of Shares Outstanding, Basic and Diluted	53.8	53.8
Net Income (Loss), Per Outstanding Limited Partnership and General Partnership Unit, Basic and Diluted, Net of Tax	$ 0.17	$ 0.30

Transactions With Affiliates (N

Transactions With Affiliates (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		5 Months Ended	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014	Dec. 05, 2014
Related Party Transaction [Line Items]
Interest Expense, Long-term Debt	$ 7.5			$ 19.7
Allowance for Funds Used During Construction, Capitalized Interest	$ 1.4			$ 2.4
Short-term Debt, Weighted Average Interest Rate	1.21%		1.21%	1.21%
Interest Expense, Short-term Borrowings	$ 0.2			$ 0.4
Accounts receivable-affiliated	656.7		$ 656.7	656.7
Revolving credit facility	2,600		2,600	2,600
Default Provision Floor	50		50	50
Short-term Debt	20		20	20
Short-term borrowings-affiliated	67.1		67.1	67.1
Transportation and Storage Services
Related Party Transaction [Line Items]
Accounts receivable-affiliated	13.4		13.4	13.4
Predecessor [Member]
Related Party Transaction [Line Items]
Interest Expense, Long-term Debt		$ 13.9			$ 26.1
Allowance for Funds Used During Construction, Capitalized Interest		$ 2			$ 3.2
Short-term Debt, Weighted Average Interest Rate		0.64%			0.64%
Interest Expense, Short-term Borrowings		$ 0.7			$ 1.8
Accounts receivable-affiliated						$ 153.8
Short-term Debt						0
Short-term borrowings-affiliated						247.3
Predecessor [Member] | Transportation and Storage Services
Related Party Transaction [Line Items]
Accounts receivable-affiliated						28.8
Columbia OpCo
Related Party Transaction [Line Items]
Reimbursement of Preformation Capital			500
Money Pool
Related Party Transaction [Line Items]
Accounts receivable-affiliated	643.2		643.2	643.2
Revolving credit facility	750		750	750
Money Pool | Predecessor [Member]
Related Party Transaction [Line Items]
Accounts receivable-affiliated						$ 125
Revolving Credit Facility
Related Party Transaction [Line Items]
Revolving credit facility	$ 500		$ 500	$ 500			$ 1,500
Notes Due 2016 [1]
Related Party Transaction [Line Items]
Debt Instrument, Maturity Date				Dec. 31, 2016
London Interbank Offered Rate (LIBOR)
Related Party Transaction [Line Items]
Basis Spread on Variable Rate				1.00%
London Interbank Offered Rate (LIBOR) | Notes Due 2016 [1]
Related Party Transaction [Line Items]
Basis Spread on Variable Rate				1.50%

Transactions With Affiliates (S

Transactions With Affiliates (Schedule of Affiliated Transactions) (Details) - Related Party Transaction [Domain] - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Related Party Transaction [Line Items]
Transportation revenues-affiliated	$ 18.4		$ 47.1
Storage revenues	12.9		26.2
Other revenues	0.1		0.2
Operation and maintenance-affiliated	38.6		74.7
Interest expense	6.3		17.7
Interest income	2.3		3.3
Accounts receivable	656.7		656.7
Current portion of long-term debt-affiliated	0		0
Short-term Debt	20		20
Short-term borrowings-affiliated	67.1		67.1
Accounts payable	41.5		41.5
Long-term debt	$ 630.9		$ 630.9
Predecessor [Member]
Related Party Transaction [Line Items]
Transportation revenues-affiliated		$ 18.9		$ 47.5
Storage revenues		13.2		26.9
Other revenues		0.1		0.2
Operation and maintenance-affiliated		29.5		57.8
Interest expense		12.6		24.7
Interest income		$ 0.1		$ 0.2
Accounts receivable					$ 153.8
Current portion of long-term debt-affiliated					115.9
Short-term Debt					0
Short-term borrowings-affiliated					247.3
Accounts payable					49.9
Long-term debt					$ 1,472.8

Transactions With Affiliates 49

Transactions With Affiliates (Schedule of Long-term Debt) (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2015	Dec. 31, 2014
Schedule of Related Party Transactions, Long-Term Debt [Line Items]
Long-term Debt	$ 630.9
Notes Due 2015
Schedule of Related Party Transactions, Long-Term Debt [Line Items]
Debt Instrument, Issuance Date	Nov. 28, 2005
Debt Instrument, Interest Rate, Stated Percentage	5.41%
Debt Instrument, Maturity Date	Nov. 30, 2015
Long-term Debt	$ 0
Notes Due 2016
Schedule of Related Party Transactions, Long-Term Debt [Line Items]
Debt Instrument, Issuance Date	Nov. 28, 2005
Debt Instrument, Interest Rate, Stated Percentage	5.45%
Debt Instrument, Maturity Date	Nov. 28, 2016
Long-term Debt	$ 0
Notes Due 2025
Schedule of Related Party Transactions, Long-Term Debt [Line Items]
Debt Instrument, Issuance Date	Nov. 28, 2005
Debt Instrument, Interest Rate, Stated Percentage	5.92%
Debt Instrument, Maturity Date	Nov. 28, 2025
Long-term Debt	$ 0
Notes Due 2032
Schedule of Related Party Transactions, Long-Term Debt [Line Items]
Debt Instrument, Issuance Date	Nov. 28, 2012
Debt Instrument, Interest Rate, Stated Percentage	4.63%
Debt Instrument, Maturity Date	Nov. 28, 2032
Long-term Debt	$ 0
Notes Due 2037
Schedule of Related Party Transactions, Long-Term Debt [Line Items]
Debt Instrument, Issuance Date	Nov. 28, 2012
Debt Instrument, Interest Rate, Stated Percentage	4.94%
Debt Instrument, Maturity Date	Nov. 30, 2037
Long-term Debt	$ 0
Notes Due 2037 [1]
Schedule of Related Party Transactions, Long-Term Debt [Line Items]
Debt Instrument, Issuance Date	Dec. 19, 2012
Debt Instrument, Interest Rate, Stated Percentage	5.16%
Debt Instrument, Maturity Date	Dec. 21, 2037
Long-term Debt	$ 0
Notes Due 2042
Schedule of Related Party Transactions, Long-Term Debt [Line Items]
Debt Instrument, Issuance Date	Nov. 28, 2012
Debt Instrument, Interest Rate, Stated Percentage	5.26%
Debt Instrument, Maturity Date	Nov. 28, 2042
Long-term Debt	$ 0
Notes Due 2042 [1]
Schedule of Related Party Transactions, Long-Term Debt [Line Items]
Debt Instrument, Issuance Date	Dec. 19, 2012
Debt Instrument, Interest Rate, Stated Percentage	5.49%
Debt Instrument, Maturity Date	Dec. 18, 2042
Long-term Debt	$ 0
Notes Due 2016 [1]
Schedule of Related Party Transactions, Long-Term Debt [Line Items]
Debt Instrument, Issuance Date	Dec. 9, 2013
Debt Instrument, Interest Rate, Stated Percentage	4.75%
Debt Instrument, Maturity Date	Dec. 31, 2016
Long-term Debt	$ 630.9
Predecessor [Member]
Schedule of Related Party Transactions, Long-Term Debt [Line Items]
Long-term Debt		$ 1,588.7
Predecessor [Member] | Notes Due 2015
Schedule of Related Party Transactions, Long-Term Debt [Line Items]
Long-term Debt		115.9
Predecessor [Member] | Notes Due 2016
Schedule of Related Party Transactions, Long-Term Debt [Line Items]
Long-term Debt		45.3
Predecessor [Member] | Notes Due 2025
Schedule of Related Party Transactions, Long-Term Debt [Line Items]
Long-term Debt		133.5
Predecessor [Member] | Notes Due 2032
Schedule of Related Party Transactions, Long-Term Debt [Line Items]
Long-term Debt		45
Predecessor [Member] | Notes Due 2037
Schedule of Related Party Transactions, Long-Term Debt [Line Items]
Long-term Debt		95
Predecessor [Member] | Notes Due 2037 [1]
Schedule of Related Party Transactions, Long-Term Debt [Line Items]
Long-term Debt		55
Predecessor [Member] | Notes Due 2042
Schedule of Related Party Transactions, Long-Term Debt [Line Items]
Long-term Debt		170
Predecessor [Member] | Notes Due 2042 [1]
Schedule of Related Party Transactions, Long-Term Debt [Line Items]
Long-term Debt		95
Predecessor [Member] | Notes Due 2016 [1]
Schedule of Related Party Transactions, Long-Term Debt [Line Items]
Long-term Debt		$ 834

Short-Term Borrowings (Narrativ

Short-Term Borrowings (Narrative) (Details) $ in Millions	6 Months Ended
	Jun. 30, 2015USD ($)	Dec. 05, 2014USD ($)
Short-term Debt [Line Items]
Revolving credit facility	$ 2,600
Default Provision Floor	$ 50
Minimum
Short-term Debt [Line Items]
Line of Credit Facility, Commitment Fee Percentage	0.125%
Maximum
Short-term Debt [Line Items]
Line of Credit Facility, Commitment Fee Percentage	0.35%
Ratio of Indebtedness to Net Capital	1
Line of Credit [Member]
Short-term Debt [Line Items]
Line of Credit	$ 20
Revolving Credit Facility
Short-term Debt [Line Items]
Revolving credit facility	500	$ 1,500
Letters of Credit Outstanding	0
Letter of Credit
Short-term Debt [Line Items]
Revolving credit facility	$ 50
Period 1 | Minimum
Short-term Debt [Line Items]
Ratio of Indebtedness to Net Capital	5.75
Period 1 | Maximum
Short-term Debt [Line Items]
Ratio of Indebtedness to Net Capital	1
Period 2 | Minimum
Short-term Debt [Line Items]
Ratio of Indebtedness to Net Capital	5.50
Period 2 | Maximum
Short-term Debt [Line Items]
Ratio of Indebtedness to Net Capital	1
Period 3 | Minimum
Short-term Debt [Line Items]
Ratio of Indebtedness to Net Capital	5
Acquisition Period | Minimum
Short-term Debt [Line Items]
Ratio of Indebtedness to Net Capital	5.50
Acquisition Period | Maximum
Short-term Debt [Line Items]
Ratio of Indebtedness to Net Capital	1
Federal Funds Effective Swap Rate
Short-term Debt [Line Items]
Basis Spread on Variable Rate	0.50%
Federal Funds Effective Swap Rate | Minimum
Short-term Debt [Line Items]
Margin Rate	0.00%
Federal Funds Effective Swap Rate | Maximum
Short-term Debt [Line Items]
Margin Rate	0.65%
London Interbank Offered Rate (LIBOR)
Short-term Debt [Line Items]
Basis Spread on Variable Rate	1.00%
London Interbank Offered Rate (LIBOR) | Minimum
Short-term Debt [Line Items]
Margin Rate	0.00%
London Interbank Offered Rate (LIBOR) | Maximum
Short-term Debt [Line Items]
Margin Rate	0.65%
Eurodollar | Minimum
Short-term Debt [Line Items]
Margin Rate	1.00%
Eurodollar | Maximum
Short-term Debt [Line Items]
Margin Rate	1.65%

Gain On Sale Of Assets (Narrati

Gain On Sale Of Assets (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Gain On Sale of Assets [Abstract]
Gain on Conveyances	$ 8.3	$ 0.3	$ 13.6	$ 17.8
Deferred Gains On Conveyances	$ 10.9		$ 10.9		$ 19.6

Goodwill (Narrative) (Details)

Goodwill (Narrative) (Details) $ in Millions	Jun. 30, 2015USD ($)
Goodwill [Line Items]
Goodwill	$ 1,975.5

Asset Retirement Obligations (C

Asset Retirement Obligations (Changes In Company's Liability For Asset Retirement Obligations) (Details) - USD ($) $ in Millions		6 Months Ended
		Jun. 30, 2015	Jun. 30, 2014
Beginning Balance		$ 23.2
Noncontributed net parent investment adjustments	[1]	(0.4)
Accretion expense		0.6
Additions		0.4
Settlements		0
Change in estimated cash flows		0
Ending Balance		23.8
Predecessor [Member]
Beginning Balance		$ 23.2	$ 26.3
Noncontributed net parent investment adjustments	[1]		0
Accretion expense			0.8
Additions			2
Settlements			0
Change in estimated cash flows			(0.2)
Ending Balance			$ 28.9
[1]	Reflects the removal of amounts related to Crossroads Pipeline Company, which was included in the Predecessor but was not contributed to the Partnership.

Regulatory Matters (Narrative)

Regulatory Matters (Narrative) (Details) - USD ($) $ in Millions	Jan. 01, 2015	Feb. 01, 2015
Regulatory Assets and Liabilities Disclosure [Abstract]
Expected Modernization Investment	$ 300
Modernization Program Recovery		$ 320

Equity Method Investments (Narr

Equity Method Investments (Narrative) (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended		5 Months Ended	6 Months Ended
	Feb. 11, 2015	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2015	Jun. 30, 2014
Schedule of Equity Method Investments [Line Items]
Contributions	$ 1,217.3
Distributions				$ (9.2)
Millennium Pipeline
Schedule of Equity Method Investments [Line Items]
Contributions		$ 0	$ 0		$ 0	$ 2.6
Distributions		7.6	4.8		24.2	11.9
Hardy Storage [Member]
Schedule of Equity Method Investments [Line Items]
Contributions		0	0		0	0
Distributions		0.5	0.5		1	1
Pennant [Member]
Schedule of Equity Method Investments [Line Items]
Contributions		0	23.8		0	52.2
Distributions		1.5	$ 0		2.7	$ 0
Proceeds from Equity Method Investment, Dividends or Distributions, Return of Capital		$ 0.9			$ 2.2

Income Taxes (Narrative) (Detai

Income Taxes (Narrative) (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Income Taxes [Line Items]
Effective income tax rates	0.00%	36.70%	9.00%	37.20%
Corporate Income Tax Rate			35.00%	35.00%

Pension And Other Postretirem57

Pension And Other Postretirement Benefits (Narrative) (Details) $ in Millions	6 Months Ended
	Jun. 30, 2015USD ($)
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	$ 0
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	$ 3

Pension And Other Postretirem58

Pension And Other Postretirement Benefits (Components Of The Plans' Net Periodic Benefits Cost) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service Cost	$ 1.3		$ 2.6
Interest cost	3		6.1
Expected return on assets	(6.1)		(12.2)
Amortization of prior service credit	(0.2)		(0.4)
Recognized actuarial loss	2.1		4.1
Total Net Periodic Benefits Cost	0.1		0.2
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service Cost	0.3		0.6
Interest cost	1		2
Expected return on assets	(4.3)		(8.6)
Amortization of prior service credit	0		0
Recognized actuarial loss	0		0
Total Net Periodic Benefits Cost	$ (3)		$ (6)
Predecessor [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service Cost		$ 1.2		$ 2.4
Interest cost		3.5		6.9
Expected return on assets		(6)		(11.9)
Amortization of prior service credit		(0.3)		(0.5)
Recognized actuarial loss		1.7		3.3
Total Net Periodic Benefits Cost		0.1		0.2
Predecessor [Member] | Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service Cost		0.2		0.5
Interest cost		1.2		2.4
Expected return on assets		(4)		(8.1)
Amortization of prior service credit		0		0
Recognized actuarial loss		0		0
Total Net Periodic Benefits Cost		$ (2.6)		$ (5.2)

Fair Value (Carrying Amount And

Fair Value (Carrying Amount And Estimated Fair Values Of Financial Instruments) (Details) - USD ($) $ in Millions	Jun. 30, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
Current portion of long-term debt	$ 0
Current Portion of Long Term Debt, Fair Value	0
Long-term debt, Carrying Amount	630.9
Long-term debt, Estimated Fair Value	$ 630.9
Predecessor [Member]
Debt Instrument [Line Items]
Current portion of long-term debt		$ 115.9
Current Portion of Long Term Debt, Fair Value		120
Long-term debt, Carrying Amount		1,472.8
Long-term debt, Estimated Fair Value		$ 1,550.4

Other Commitments And Conting60

Other Commitments And Contingencies (Narrative) (Details) - USD ($) $ in Millions	Jun. 30, 2015	Dec. 05, 2014
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 2,600
Line of Credit [Member]
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Line of Credit	20
Revolving Credit Facility [Member]
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	500	$ 1,500
Guarantee Obligations Maximum Exposure Year One	0
Letter of Credit
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 50

Other Commitments And Conting61

Other Commitments And Contingencies (Existence and Expiration of Commercial Commitments) (Details) $ in Millions	Jun. 30, 2015USD ($)
Other Commitments and Contingencies [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	$ 2,770
Guarantee Obligations Maximum Exposure Year One	20
Guarantee Obligations Maximum Exposure Year Two	0
Guarantee Obligations Maximum Exposure Year Three	0
Guarantee Obligations Maximum Exposure Year Four	500
Guarantee Obligations Maximum Exposure Year Five	0
Guarantee Obligations Maximum Exposure Thereafter	2,250
Guarantee of Indebtedness of Others [Member]
Other Commitments and Contingencies [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	2,750
Guarantee Obligations Maximum Exposure Year One	0
Guarantee Obligations Maximum Exposure Year Two	0
Guarantee Obligations Maximum Exposure Year Three	0
Guarantee Obligations Maximum Exposure Year Four	500
Guarantee Obligations Maximum Exposure Year Five	0
Guarantee Obligations Maximum Exposure Thereafter	2,250
Line of Credit [Member]
Other Commitments and Contingencies [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	20
Guarantee Obligations Maximum Exposure Year Two	0
Guarantee Obligations Maximum Exposure Year Three	0
Guarantee Obligations Maximum Exposure Year Four	0
Guarantee Obligations Maximum Exposure Year Five	0
Guarantee Obligations Maximum Exposure Thereafter	0
Line of Credit [Member]
Other Commitments and Contingencies [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	$ 20

Accumulated Other Comprehensi62

Accumulated Other Comprehensive Loss (Narrative) (Details) - Millennium Pipeline - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
Accumulated Other Comprehensive Loss [Line Items]
Other Comprehensive Income Unrecognized Gain Loss On Derivatives Arising During Period Net Of Tax	$ 25.9	$ 16.6
Debt Instrument, Maturity Date	Jun. 1, 2025

Accumulated Other Comprehensi63

Accumulated Other Comprehensive Loss (Components Of Accumulated Other Comprehensive Loss) (Details) - USD ($) $ in Millions		1 Months Ended	3 Months Ended				5 Months Ended	6 Months Ended
		Feb. 11, 2015	Jun. 30, 2015		Jun. 30, 2014		Jun. 30, 2015	Jun. 30, 2015		Jun. 30, 2014
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	[1]	$ (16.7)	$ (4.2)					$ (16.7)
Predecessor net tax liabilities not assumed by Columbia OpCo	[2]	1,222.2
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	[1]		0					0
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	[1],[3]		0.5					0.6
Other Comprehensive Income (Loss), Net of Tax		0.1	0.5	[1]			$ 0.5			$ 0.6	[1]
Allocation of Accumulated Other Comprehensive Loss To Noncontrolling Interest			0.4	[1]			0	(22.3)	[1]
Ending Balance	[1]		(4.1)				(4.1)	(4.1)
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	[1]	(16.6)	(4.1)					(16.6)
Predecessor net tax liabilities not assumed by Columbia OpCo	[1],[2]							(10.2)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	[1]		0					0
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	[1],[3]		0.5					0.6
Other Comprehensive Income (Loss), Net of Tax	[1]		0.5					0.6
Allocation of Accumulated Other Comprehensive Loss To Noncontrolling Interest	[1]		0.4					(22.2)
Ending Balance	[1]		(4)				(4)	(4)
Accumulated Defined Benefit Plans Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	[1]	(0.1)	(0.1)					(0.1)
Predecessor net tax liabilities not assumed by Columbia OpCo	[1],[2]							(0.1)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	[1]		0					0
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	[1],[3]		0					0
Other Comprehensive Income (Loss), Net of Tax	[1]		0					0
Allocation of Accumulated Other Comprehensive Loss To Noncontrolling Interest	[1]		0					(0.1)
Ending Balance	[1]		$ (0.1)				(0.1)	(0.1)
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Predecessor net tax liabilities not assumed by Columbia OpCo	[2]	(10.3)						(10.3)	[1]
Other Comprehensive Income (Loss), Net of Tax		0.1					0.1
Allocation of Accumulated Other Comprehensive Loss To Noncontrolling Interest							$ 22.7
Predecessor [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance		$ (16.7)			$ (17.4)	[1]		$ (16.7)		(17.7)	[1]
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	[1]				0					0
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	[1]				0.2					0.5
Other Comprehensive Income (Loss), Net of Tax	[1]				0.2					0.5
Ending Balance	[1]				(17.2)					(17.2)
Predecessor [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	[1]				(17.3)					(17.6)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	[1]				0					0
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	[1]				0.2					0.5
Other Comprehensive Income (Loss), Net of Tax	[1]				0.2					0.5
Ending Balance	[1]				(17.1)					(17.1)
Predecessor [Member] | Accumulated Defined Benefit Plans Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	[1]				(0.1)					(0.1)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	[1]				0					$ 0
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	[1]				0
Other Comprehensive Income (Loss), Net of Tax	[1]				0					$ 0
Ending Balance	[1]				$ (0.1)					$ (0.1)
[1]	All amounts prior to the IPO are net of tax. Amounts in parentheses indicate debits.
[2]	Reflects the non-cash elimination of all historical current and deferred income taxes other than Tennessee state income taxes that continue to be borne by the Partnership post-IPO, as well as associated regulatory assets and liabilities.
[3]	Includes amounts allocated to noncontrolling interest.

Other, Net (Schedule of Other,

Other, Net (Schedule of Other, Net) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Schedule Of Other, Net [Line Items]
AFUDC Equity	$ 4.9		$ 8.4
Miscellaneous	0		0.8
Total Other, net	$ 4.9		$ 9.2
Predecessor [Member]
Schedule Of Other, Net [Line Items]
AFUDC Equity		$ 2.7		$ 4.3
Miscellaneous		(0.1)		0.1
Total Other, net		$ 2.6		$ 4.4

Supplemental Cash Flow Inform65

Supplemental Cash Flow Information (Details) - USD ($) $ in Millions		6 Months Ended
		Jun. 30, 2015	Jun. 30, 2014
Supplemental Cash Flow [Line Items]
Capital expenditures included in current liabilities	[1]	$ 184.5
Cash paid for interest, net of interest capitalized amounts		21.3
Cash paid for income taxes		$ 0
Predecessor [Member]
Supplemental Cash Flow [Line Items]
Capital expenditures included in current liabilities	[1]		$ 94
Cash paid for interest, net of interest capitalized amounts			27.7
Cash paid for income taxes			$ 35.7
[1]	Capital expenditures included in current liabilities is comprised of "Accrued capital expenditures" and certain other amounts included within "Accounts payable" on the Condensed Consolidated and Combined Balance Sheet (unaudited).

Concentration Of Credit Risk (N

Concentration Of Credit Risk (Narrative) (Details)	6 Months Ended
	Jun. 30, 2015
Concentration Risk [Line Items]
Concentration Risk, Benchmark Description	0.1

Concentration of Credit Risk (S

Concentration of Credit Risk (Schedule of Concentration Of Credit Risk) (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Concentration Risk [Line Items]
Revenues		$ 315.6		$ 654.8
Credit Concentration Risk
Concentration Risk [Line Items]
Revenues	[1]	$ 36.2		$ 85.1
Concentration Risk, Percentage	[1]	11.50%		13.00%
Predecessor [Member]
Concentration Risk [Line Items]
Revenues			$ 343.4		$ 688.9
Predecessor [Member] | Credit Concentration Risk
Concentration Risk [Line Items]
Revenues	[1]		$ 36		$ 83.6
Concentration Risk, Percentage	[1]		10.50%		12.10%
[1]	(1) Represents the gross amount of revenue contracted for with Columbia Gas of Ohio and, therefore, subject to risk at the loss of this customer. Columbia Gas of Ohio has entered into certain capacity release arrangements with third parties which ultimately can decrease the net revenue amount we receive from Columbia Gas of Ohio in any given period.

Subsequent Events (Narrative) (

Subsequent Events (Narrative) (Details) $ / shares in Units, shares in Millions, $ in Millions	Jul. 30, 2015USD ($)$ / shares	Jul. 02, 2015	Jul. 01, 2015USD ($)shares	Jun. 30, 2015USD ($)	Jun. 30, 2014USD ($)	Jun. 30, 2015USD ($)	Jun. 30, 2014USD ($)
Subsequent Event [Line Items]
Gain on Conveyances				$ 8.3	$ 0.3	$ 13.6	$ 17.8
Subsequent Event [Member]
Subsequent Event [Line Items]
Distribution Made to Limited Partner, Distributions Declared, Per Unit | $ / shares	$ 0.1675
Distribution Made to Limited Partner, Cash Distributions Declared	$ 16.9
Distribution Made to Limited Partner, Distribution Date	Aug. 20, 2015
Distribution Made to Limited Partner, Date of Record	Aug. 13, 2015
Share Distribution, Date			Jul. 1, 2015
Common Stock, Shares Authorized | shares			317.6
Common Stock, Shares, Issued | shares			317.6
Distribution Payable Shareholder Date of Record			Jun. 19, 2015
Stock Trade Date		Jul. 2, 2015
Acres Conveyed			20,000
Gain on Conveyances			$ 35.8