Columbia Pipeline (CPGX) 10-Q 3 May 16 2016 Q1 Quarterly report Financial data

Document And Entity Information

Document And Entity Information - shares	3 Months Ended
	Mar. 31, 2016	Apr. 29, 2016
Document Information [Line Items]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2016
Document Fiscal Year Focus	2,016
Document Fiscal Period Focus	Q1
Entity Registrant Name	COLUMBIA PIPELINE GROUP, INC./DE
Entity Central Index Key	1,629,995
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Units Outstanding		400,383,243

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Millions		Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015	Dec. 31, 2014
Current Assets
Cash and cash equivalents		$ 640.9	$ 930.9	$ 7.3	$ 0.5
Accounts receivable (less reserve of $0.3 and $0.6, respectively)		161.5	152.4
Materials and supplies, at average cost		33.2	32.8
Exchange gas receivable		12	19
Deferred property taxes		54.2	52
Prepayments and other		46.5	48.5
Total Current Assets		948.3	1,235.6
Investments
Unconsolidated affiliates		437.3	438.1
Other investments		13.8	13.8
Total Investments		451.1	451.9
Property, Plant and Equipment
Property, plant and equipment		9,426	9,052.3
Accumulated depreciation and amortization		(3,025.1)	(2,988.6)
Net Property, Plant and Equipment		6,400.9	6,063.7
Other Noncurrent Assets
Regulatory assets		182.2	177.7
Goodwill		1,975.5	1,975.5
Postretirement and postemployment benefits assets		117.7	115.7
Deferred charges and other		15.4	15.5
Total Other Noncurrent Assets		2,290.8	2,284.4
Total Assets		10,091.1	10,035.6
Current Liabilities
Short-term borrowings		15	15
Accounts payable		58.7	56.8
Dividends payable		53.6	0
Customer deposits		18.8	17.9
Taxes accrued		101	106
Interest accrued		37.2	9.5
Exchange gas payable		12.1	18.6
Deferred revenue		10.5	15
Accrued capital expenditures		88.7	100.1
Accrued compensation and related costs		28.5	51.9
Other accruals		89.9	70
Total Current Liabilities		514	460.8
Noncurrent Liabilities
Long-term debt		2,725.9	2,725.6
Deferred income taxes		1,395.3	1,348.1
Accrued liability for postretirement and postemployment benefits		48.9	49.4
Regulatory liabilities		303.6	321.6
Asset retirement obligations		25.1	25.7	23.5	23.2
Other noncurrent liabilities		94.4	91.4
Total Noncurrent Liabilities		4,593.2	4,561.8
Total Liabilities		5,107.2	5,022.6
Equity
Common stock, $0.01 par value, 2,000,000,000 shares authorized; 400,383,243 and 399,841,350 shares outstanding, respectively		4	4
Additional paid-in capital		4,037.1	4,032.7
Retained earnings		14	46.9
Treasury stock		(6)	0
Accumulated other comprehensive loss	[1]	(26.6)	(27)	(25.1)	(34.5)
Total CPG Equity		4,022.5	4,056.6
Noncontrolling Interest		961.4	956.4
Total Equity		4,983.9	5,013	$ 4,949	$ 4,176.3
Total Liabilities and Equity		$ 10,091.1	$ 10,035.6
[1]	All amounts are net of tax. Amounts in parentheses indicate debits.

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Statement of Financial Position [Abstract]
Accounts receivable less reserve	$ 0.3	$ 0.6
Common Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01
Common Stock, Shares Authorized	2,000,000,000	2,000,000,000
Common Stock, Shares, Outstanding	400,383,243	399,841,350

Statements of Consolidated Oper

Statements of Consolidated Operations - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Operating Revenues
Transportation revenues	$ 308.5	$ 248.4
Transportation revenues-affiliated	0	29
Storage revenues	49.9	36.6
Storage revenues-affiliated	0	13.3
Other revenues	6.1	12.7
Total Operating Revenues	364.5	340
Operating Expenses
Operation and maintenance	169.1	118.4
Operation and maintenance-affiliated	0	28
Depreciation and amortization	40.4	32.5
Gain on sale of assets	(2.6)	(5.3)
Property and other taxes	21.8	19.1
Total Operating Expenses	228.7	192.7
Equity Earnings in Unconsolidated Affiliates	15.9	15.4
Operating Income	151.7	162.7
Other Income (Deductions)
Interest expense	(29.4)	0
Interest expense-affiliated	0	(18.3)
Other, net	7	4.6
Total Other Deductions, net	(22.4)	(13.7)
Income from Continuing Operations before Income Taxes	129.3	149
Income Taxes	42.7	51.9
Income from Continuing Operations	86.6	97.1
Income from Discontinued Operations-net of taxes	0.2	0
Net Income	86.8	97.1
Less: Net income attributable to noncontrolling interest	14.6	7.1
Net income attributable to CPG	72.2	90
Amounts Attributable to CPG
Income from continuing operations	72	90
Income from Discontinued Operations-net of taxes	0.2	0
Net income attributable to CPG	$ 72.2	$ 90
Basic Earnings Per Share
Continuing operations	$ 0.18	$ 0.28
Discontinued operations	0	0
Basic Earnings Per Share	0.18	0.28
Diluted Earnings Per Share
Continuing Operations	0.18	0.28
Discontinued Operations	0	0
Diluted Earnings Per Share	$ 0.18	$ 0.28
Basic Average Common Shares Outstanding	400.3	317.6
Diluted Average Common Shares	400.7	317.6
Dividends Declared Per Common Share	$ 0.26	$ 0

Statements of Consolidated Comp

Statements of Consolidated Comprehensive Income - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2016	Mar. 31, 2015
Statement of Comprehensive Income [Abstract]
Net Income		$ 86.8	$ 97.1
Net unrealized gain on cash flow hedges	[1]	0.4	0.2
Unrecognized pension and OPEB benefit	[2],[3]	0.1	7
Total other comprehensive income	[4]	0.5	7.2
Total comprehensive income		87.3	104.3
Less: Comprehensive Income-noncontrolling interest		14.7	7.1
Comprehensive Income-controlling interests		$ 72.6	$ 97.2
[1]	Net unrealized gains on derivatives qualifying as cash flow hedges, net of $0.2 million and $0.1 million tax expense for the three months ended March 31, 2016 and 2015, respectively.
[2]	Unrecognized pension and OPEB benefits are primarily related to pension and OPEB remeasurements recorded during 2016 and 2015.
[3]	Unrecognized pension and other postretirement benefit (“OPEB”) benefits, net of $0.1 million and zero tax expense for the three months ended March 31, 2016 and 2015, respectively.
[4]	All amounts are net of tax. Amounts in parentheses indicate debits.

Statements of Consolidated Com6

Statements of Consolidated Comprehensive Income (Parenthetical) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Statement of Comprehensive Income [Abstract]
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Tax	$ 0.2	$ 0.1
Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Tax	$ 0.1	$ 0

Statements of Consolidated Cash

Statements of Consolidated Cash Flows - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Operating Activities
Net Income	$ 86.8	$ 97.1
Adjustments to Reconcile Net Income to Net Cash from Continuing Operations:
Depreciation and amortization	40.4	32.5
Deferred income taxes and investment tax credits	40.6	36.1
Deferred revenue	(2)	5.3
Equity-based compensation expense and profit sharing contribution	6.2	2.1
Gain on sale of assets	(2.6)	(5.3)
Income from unconsolidated affiliates	(15.9)	(15.4)
Income from discontinued operations-net of taxes	(0.2)	0
Amortization of debt related costs	1.3	0
AFUDC equity	(6.1)	(3.5)
Distributions of earnings received from equity investees	18.9	18.3
Changes in Assets and Liabilities:
Accounts receivable	(6.6)	12.2
Accounts receivable-affiliated	0	15.2
Accounts payable	(4.4)	(15.6)
Accounts payable-affiliated	0	(8.6)
Customer deposits	0.9	0.6
Taxes accrued	(5)	(8.8)
Interest accrued	27.7	0
Exchange gas receivable/payable	0.5	(0.1)
Other accruals	(19.3)	(9.1)
Prepayments and other current assets	7.1	2.7
Regulatory assets/liabilities	1.5	15.3
Postretirement and postemployment benefits	(0.1)	(8.7)
Deferred charges and other noncurrent assets	(2.3)	(0.2)
Other noncurrent liabilities	2.6	1.7
Net Operating Activities from Continuing Operations	170	163.8
Net Operating Activities from Discontinued Operations	0.3	0
Net Cash Flows from Operating Activities	170.3	163.8
Investing Activities
Capital expenditures	(388.9)	(163.9)
Change in short-term lendings-affiliated	0	(698)
Proceeds from disposition of assets	0	10.2
Contributions to equity investees	(1.9)	0
Distributions from equity investees	0.2	1.3
Other investing activities	(2)	(2.4)
Net Cash Flows used for Investing Activities	(392.6)	(852.8)
Financing Activities
Change in short-term borrowings-affiliated	0	(232.1)
Debt related costs	(0.5)	0
Issuance of long-term debt-affiliated	0	1,217.3
Payments of long-term debt-affiliated, including current portion	0	(957.8)
Proceeds from the issuance of common units, net of offering costs	0	1,168.4
Distribution of IPO proceeds to parent	0	(500)
Distribution to noncontrolling interest	(9.7)	0
Acquisition of treasury stock	(6)	0
Dividends paid - common stock	(51.5)	0
Net Cash Flows (used for) from Financing Activities	(67.7)	695.8
Change in cash and cash equivalents	(290)	6.8
Cash and cash equivalents at beginning of period	930.9	0.5
Cash and Cash Equivalents at End of Period	$ 640.9	$ 7.3

Statements of Consolidated Equi

Statements of Consolidated Equity - USD ($) shares in Millions, $ in Millions		Total		Common Stock	Treasury Stock	Additional Paid-in Capital	Retained Earnings	Parent	Accumulated Other Comprehensive Loss	Noncontrolling Interest
Beginning Balance at Dec. 31, 2014		$ 4,176.3						$ 4,210.8	$ (34.5)	$ 0
Net Income		97.1						90	0
Net income attributable to noncontrolling interest		7.1								7.1
Other comprehensive income, net of tax		7.2	[1]					0	7.2	0
Allocation of AOCI to noncontrolling interest		0						0	2.2	(2.2)
Issuance of common units of CPPL		1,168.4						0	0	1,168.4
Distribution of IPO proceeds to parent		(500)						(500)	0	0
Purchase of additional interest in Columbia OpCo	[2]	0						227.1	0	(227.1)
Ending Balance at Mar. 31, 2015		4,949						$ 4,027.9	(25.1)	946.2
Beginning Balance at Dec. 31, 2015		5,013		$ 4	$ 0	$ 4,032.7	$ 46.9		(27)	956.4
Net Income		86.8		0	0	0	72.2		0
Net income attributable to noncontrolling interest		14.6								14.6
Other comprehensive income, net of tax		0.5	[1]	0	0	0	0		0.4	0.1
Distribution of IPO proceeds to parent		0
Common stock dividends		(105.1)		0	0	0	(105.1)		0	0
Treasury stock acquired		(6)		0	(6)	0	0		0	0
Distributions to noncontrolling interest		$ (9.7)		$ 0	$ 0	$ 0	$ 0		$ 0	$ (9.7)
Long-term incentive plan		4.4		0	0	4.4	0		0	0
Ending Balance at Mar. 31, 2016		$ 4,983.9		$ 4	$ (6)	$ 4,037.1	$ 14		$ (26.6)	$ 961.4
[1]	All amounts are net of tax. Amounts in parentheses indicate debits.
[2]	Represents the sale 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 the noncontrolling interest by the same amount it increases the net parent investment because CPPL's purchase price for its additional 8.4% interest in Columbia OpCo exceeded book value.

Statements of Consolidated Equ9

Statements of Consolidated Equity (Parenthetical) $ in Millions	3 Months Ended
	Mar. 31, 2015USD ($)
Issuance of common units of CPPL	$ 1,168.4
Noncontrolling Interest
Issuance of common units of CPPL	$ 1,168.4
Columbia OpCo
Limited Liability Company (LLC) or Limited Partnership (LP), Members or Limited Partners, Ownership Interest Additional Ownership Interest	8.40%

Basis of Accounting Presentatio

Basis of Accounting Presentation	3 Months Ended
	Mar. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Accounting Presentation	Basis of Accounting Presentation Columbia Pipeline Group, Inc. ("CPG") is a growth-oriented Delaware corporation formed by NiSource on September 26, 2014 to own, operate and develop a portfolio of pipelines, storage and related midstream assets. CPG owns and operates, through its subsidiaries, approximately 15,000 miles of strategically located interstate gas pipelines extending from New York to the Gulf of Mexico and one of the nation’s largest underground natural gas storage systems, with approximately 300 MMDth of working gas capacity, as well as related gathering and processing assets. CPG indirectly owns the general partner of CPPL and all of CPPL’s subordinated units and incentive distribution rights. CPG did not have any material assets or liabilities as a separate corporate entity until the contribution of CEG from NiSource on February 11, 2015. As a result of this contribution, the financial statements for periods as of and subsequent to September 26, 2014 reflect the consolidated financial position, results of operations and cash flows for CPG. CPG is engaged in regulated 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 a tariff at rates subject to FERC approval. Separation. On June 2, 2015, NiSource announced that its board of directors approved the separation of CPG from NiSource (the “Separation”) through the distribution of CPG common stock to holders of NiSource common stock as of June 19, 2015 (the “Record Date”). On July 1, 2015, NiSource distributed, pursuant to an effective registration statement on Form 10, 317.6 million shares, one share of CPG common stock for every one share of NiSource common stock held by NiSource stockholders on the Record Date. As of July 1, 2015, CPG is an independent, publicly traded company, and NiSource does not retain any ownership interest in CPG. CPG's common stock began trading "regular-way" under the ticker symbol "CPGX" on the NYSE on July 2, 2015. In connection with the Separation, CPG completed the following transactions: • In May 2015, CPG completed its private placement of senior notes and received proceeds of approximately $2,722.3 million . CPG utilized a portion of the proceeds to repay approximately $1,087.3 million of intercompany debt and short-term borrowings, including, net amounts due from the money pool between CPG and NiSource Finance Corp. ("NiSource Finance"); • CPG further utilized the proceeds from the senior notes to make a cash distribution of approximately $1,450.0 million to NiSource; and • Accounts related to NiSource and its subsidiaries, including accounts receivable and accounts payable, were reclassified from affiliated to non-affiliated. Agreements with NiSource following the Separation . CPG entered into the Separation and Distribution Agreement and several other agreements with NiSource to effect the Separation and provide a framework for CPG’s relationship with NiSource, and its subsidiaries, after the Separation. The Separation and Distribution Agreement contains many of the key provisions related to CPG’s separation from NiSource and the distribution of CPG’s shares of common stock to NiSource’s stockholders, including cross-indemnities between CPG and NiSource. In general, NiSource has agreed to indemnify CPG for any liabilities relating to NiSource's business and CPG has agreed to indemnify NiSource for any liabilities relating to CPG's business. In addition to the Separation and Distribution Agreement, CPG entered into the following agreements with NiSource related to the Separation: • Tax Allocation Agreement - Provides for the respective rights, responsibilities, and obligations of NiSource and CPG with respect to tax liabilities and benefits, tax attributes, the preparation and filing of tax returns, tax contests, and certain other matters regarding taxes. • Employee Matters Agreement - Provides for the respective obligations to employees and former employees who are or were associated with CPG (including those employees who transferred employment from NiSource to CPG prior to the Separation) and for other employment and employee benefits matters. • Transition Services Agreement - Provides for the provision of certain transitional services by NiSource to CPG, and vice versa. The services may include the provision of administrative and other services identified by the parties. The charge for these services is expected to be based on actual costs incurred by the party rendering the services without profit. Merger. On March 17, 2016, CPG entered into an Agreement and Plan of Merger (the “Merger Agreement”), among CPG, TransCanada PipeLines Limited, a Canadian corporation (“Parent”), TransCanada PipeLine USA Ltd., a Nevada corporation and a wholly owned subsidiary of Parent (“US Parent”), Taurus Merger Sub Inc., a Delaware corporation and a wholly owned subsidiary of US Parent (“Merger Sub”), and, solely for purposes of Section 3.02, Section 5.02, Section 5.09 and Article VIII of the Merger Agreement, TransCanada Corporation, a Canadian corporation and the direct parent company of Parent ("TransCanada"). Upon the terms and subject to the conditions set forth in the Merger Agreement, Merger Sub will be merged with and into CPG (the “Merger”) with CPG surviving the Merger as an indirect wholly owned subsidiary of TransCanada. The Merger is expected to close in the second half of 2016, subject to satisfaction of customary conditions, including receipt of required regulatory and CPG shareholder approval. Following the completion of the transaction, TransCanada will own the general partner of CPPL, all of CPPL’s incentive distribution rights and all of CPPL’s subordinated units, which represent a 46.5% limited partnership interest in CPPL. The Condensed Consolidated Financial Statements (unaudited) have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission (the "SEC"). 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 CPG believes that the disclosures made are adequate to make the information not misleading. These financial statements should be read in conjunction with the Company’s audited consolidated financial statements for the year ended December 31, 2015 . These financial statements reflect all normal recurring adjustments that are, in the opinion of management, necessary to fairly present CPG’s results of operations and financial position. Amounts reported in the Condensed Statements of Consolidated Operations (unaudited) are not necessarily indicative of amounts expected for the respective annual periods. CPG’s accompanying Condensed Consolidated Financial Statements (unaudited) have been prepared in accordance with GAAP on the basis of NiSource’s historical ownership of CPG’s assets and its operations. These financial statements include the accounts of the following subsidiaries: Columbia Gas Transmission, Columbia Gulf, Columbia Midstream, CEVCO, CNS Microwave, Crossroads, CPGSC, CEG, Columbia Remainder Corporation, CPP GP LLC, CPPL, OpCo GP, Columbia OpCo and CPG. All intercompany transactions and balances have been eliminated. Also included in the Condensed Consolidated Financial Statements (unaudited) are equity method investments Hardy Storage, Millennium Pipeline and Pennant.

CPPL Initial Public Offering

CPPL Initial Public Offering	3 Months Ended
	Mar. 31, 2016
Equity [Abstract]
CPPL Initial Public Offering	CPPL Initial Public Offering On December 5, 2007, NiSource formed CPPL (NYSE: CPPL) to own, operate and develop a portfolio of pipelines, storage and related assets. On February 11, 2015 , CPPL completed its offering of 53.8 million common units representing limited partner interests, constituting 53.5% of CPPL's outstanding limited partner interests. CPPL received $1,168.4 million of net proceeds from IPO. CPG owns the general partner of CPPL and all of CPPL's subordinated units and incentive distribution rights. The assets of CPPL consist of a 15.7% limited partner interest in Columbia OpCo, which prior to the Separation, consisted of substantially all of NiSource's Columbia Pipeline Group Operations segment. The operations of CPPL are consolidated in CPG’s results. As of March 31, 2016 , the portion of CPPL owned by the public is reflected as a noncontrolling interest in the Condensed Consolidated Financial Statements (unaudited). The table below summarizes the effects of changes in CPG’s ownership interest in Columbia OpCo on equity: Three Months Ended (in millions) 2016 2015 Net income attributable to CPG $ 72.2 $ 90.0 Increase in CPG’s net parent investment for the sale of 8.4% of Columbia OpCo — 227.1 Change from net income attributable to CPG and transfers to noncontrolling interest $ 72.2 $ 317.1

Recent Accounting Pronouncement

Recent Accounting Pronouncements	3 Months Ended
	Mar. 31, 2016
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
Recent Accounting Pronouncements	Recent Accounting Pronouncements In March 2016, the FASB issued ASU 2016-09, Improvements to Employee Share-Based Payment Accounting (Topic 718) . ASU 2016-09 simplifies several aspects of the accounting for employee share-based payment transactions, including the accounting for income taxes, forfeitures and statutory tax withholding requirements, as well as classification in the statement of cash flows. CPG is required to adopt ASU 2016-09 for periods beginning after December 15, 2016, including interim periods, with early adoption permitted. CPG is currently evaluating the impact the adoption of ASU 2016-09 will have on the Condensed Consolidated Financial Statements (unaudited) or Notes to Condensed Consolidated Financial Statements (unaudited). 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 August 2015, the FASB issued ASU 2015-14 to extend 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 permitted on the original effective date of ASU 2014-09 on a limited basis. In March 2016, the FASB issued ASU 2016-08, which amends the principal-versus-agent implementation guidance and illustrations in ASU 2014-09. Among other things, ASU 2016-08 clarifies that an entity should evaluate whether it is the principal or the agent for each specified good or service promised in a contract with a customer. As defined in ASU 2016-08, a specified good or service is "a distinct good or service (or a distinct bundle of goods or services) to be provided to the customer." Therefore, for contracts involving more than one specified good or service, the entity may be the principal for one or more specified goods or services and the agent for others. ASU 2016-08 has the same effective date as ASU 2014-09, as amended by ASU 2015-14. CPG is required to adopt ASU 2016-08 using the same transition method it uses to adopt ASU 2014-09. CPG is currently evaluating the impact the adoption of ASU 2014-09, ASU 2015-14 and ASU 2016-08 will have on the Condensed Consolidated Financial Statements (unaudited) or Notes to Condensed Consolidated Financial Statements (unaudited). In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842) . ASU 2016-02 introduces a lessee model that brings most leases on the balance sheet. The new standard also aligns many of the underlying principles of the new lessor model with those in ASC 606, the FASB's new revenue recognition standard (e.g., those related to evaluating when profit can be recognized). Furthermore, ASU 2016-02 addresses other concerns related to the current leases model. For example, ASU 2016-02 eliminates the requirement in current U.S. GAAP for an entity to use bright-line tests in determining lease classification. The standard also requires lessors to increase the transparency of their exposure to changes in value of their residual assets and how they manage that exposure. CPG is required to adopt ASU 2016-02 for periods beginning after December 15, 2018, including interim periods, with early adoption permitted. CPG is currently evaluating the impact the adoption of ASU 2016-02 will have on the Condensed Consolidated Financial Statements (unaudited) or Notes to Condensed Consolidated 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. In August 2015, the FASB issued ASU 2015-15 to clarify the SEC staff's position on these costs in relation to line-of-credit agreements stating that the SEC staff would not object to an entity deferring and presenting debt issuance costs related to a line-of-credit arrangement as an asset and subsequently amortizing the deferred debt issuance costs ratably over the term of such arrangement, regardless of whether there are any outstanding borrowings on the line-of-credit. CPG adopted ASU 2015-03 and ASU 2015-15 as of January 1, 2016, resulting in the reclassification of unamortized balance of debt issuance costs from "Deferred charges and other" to "Long-term debt." This change in accounting principle was applied retrospectively. As of December 31, 2015, the balance of unamortized debt issuance costs recorded in "Deferred charges and other" was $20.6 million . As a result of the retrospective adjustment, the December 31, 2015 balances of "Deferred charges and other" and "Long-term debt" were reduced by $20.6 million on the Condensed Consolidated Balance Sheets (unaudited) and Notes to Condensed Consolidated 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. CPG retrospectively adopted ASU 2015-02 as of January 1, 2016. The adoption of this guidance did not have a material impact on the Condensed Consolidated Financial Statements (unaudited) or Notes to Condensed Consolidated Financial Statements (unaudited).

Earnings Per Share

Earnings Per Share	3 Months Ended
	Mar. 31, 2016
Earnings Per Share [Abstract]
Earnings Per Share	Earnings Per Share Basic EPS is based on net income attributable to CPG and is calculated based upon the daily weighted-average number of common shares outstanding during the periods presented. Also, this calculation includes fully vested awards that have not yet been issued as common stock. Diluted EPS includes the above, plus unvested stock awards granted under CPG's compensation plans, but only to the extent these instruments dilute earnings per share. On July 1, 2015, 317.6 million shares of CPG common stock were distributed to NiSource stockholders in conjunction with the Separation. For comparative purposes, and to provide a more meaningful calculation for weighted average shares, CPG has assumed this amount to be outstanding as of the beginning of each period prior to the Separation presented in the calculation of weighted average shares outstanding. The calculation of diluted average common shares is as follows: Three Months Ended (in millions) 2016 2015 Basic average common shares outstanding 400.3 317.6 Dilutive potential common shares: Shares restricted under stock plans 0.4 — Diluted average common shares 400.7 317.6 Dividends. CPG paid a dividend of $0.12875 per share to stockholders on February 19, 2016 . On March 22, 2016 , CPG declared a dividend of $0.13375 per share to stockholders of record at April 29, 2016 , payable May 20, 2016 .

Transactions with Affiliates

Transactions with Affiliates	3 Months Ended
	Mar. 31, 2016
Related Party Transactions [Abstract]
Transactions with Affiliates	Transactions with Affiliates Prior to the Separation, CPG engaged in transactions with subsidiaries of NiSource, which at that time were deemed to be affiliates of CPG. The Separation occurred on July 1, 2015 and for periods after this date CPG and the subsidiaries of NiSource are no longer affiliates. Transactions with affiliates prior to the Separation are summarized below: Statement of Operations Three Months Ended (in millions) 2016 2015 Transportation revenues $ — $ 29.0 Storage revenues — 13.3 Other revenues — 0.1 Operation and maintenance expense — 28.0 Interest expense — 18.3 Interest income — 1.0 Transportation, Storage and Other Revenues . CPG provided natural gas transportation, storage and other services to subsidiaries of NiSource, former affiliates. Operation and Maintenance Expense . CPG received executive, financial, legal, information technology and other administrative and general services from a former affiliate, NiSource Corporate Services. Expenses incurred as a result of these services consisted of employee compensation and benefits, outside services and other expenses. CPG was 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 . Prior to the private placement of senior notes on May 22, 2015, CPG paid NiSource interest for intercompany long-term debt outstanding. For the three months ended March 31, 2015 , CPG was charged interest for long-term debt of $19.0 million , offset by associated AFUDC of $1.0 million . Columbia OpCo and its subsidiaries entered into an intercompany money pool agreement with NiSource Finance, which became effective on the closing date of CPPL’s IPO. Following the Separation, the agreement is with CPG. 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 CPPL’s IPO, the subsidiaries of CPG participated in a similar money pool agreement with NiSource Finance. Prior to the Separation, NiSource Corporate Services administered the money pools. Prior to the Separation, the cash accounts maintained by the subsidiaries of Columbia OpCo and CPG were 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 was determined by the net position of each subsidiary in the money pool. Subsequent to the Separation, the intercompany money pool balances and related interest expense and income are eliminated as intercompany activity. The money pool weighted-average interest rate at March 31, 2015 was 1.07% . For the three months ended March 31, 2015 , the interest expense for short-term borrowings charged was $0.3 million . Dividends to NiSource . During the three months ended March 31, 2015 , CPG distributed $500.0 million of the proceeds from CPPL’s IPO to NiSource as a reimbursement of preformation capital expenditures with respect to the assets contributed to Columbia OpCo. There were no restrictions on the payment by CPG of dividends to NiSource.

Short-Term Borrowings

Short-Term Borrowings	3 Months Ended
	Mar. 31, 2016
Short-term Debt [Abstract]
Short-Term Borrowings	Short-Term Borrowings CPG Revolving Credit Facility. On December 5, 2014, CPG entered into a $1,500.0 million senior revolving credit facility, of which $250.0 million in letters of credit is available. The revolving credit facility became effective as of the Separation with a termination date of July 2, 2020. CPG expects that $750.0 million of this facility will be utilized as credit support for Columbia OpCo and its subsidiaries and the remaining $750.0 million of this facility will be available for CPG’s general corporate purposes, including working capital. The revolving credit facility will provide liquidity support for CPG's $1,000.0 million commercial paper program. Obligations under the CPG revolving credit facility are unsecured. Loans under the CPG revolving credit facility will bear interest at CPG’s option at either (i) the greatest of (a) the federal funds effective rate plus 0.500 percent , (b) the reference prime rate of JPMorgan Chase Bank, N.A., or (c) the Eurodollar rate which is based on the 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. CPG’s revolving credit facility is subject to a facility fee that varies from 0.125 percent to 0.350 percent per annum, according to CPG’s credit rating. Revolving indebtedness under the CPG credit facility will rank equally with all of CPG’s outstanding unsecured and unsubordinated debt. CEG, OpCo GP and Columbia OpCo have each fully guaranteed the CPG credit facility. The CPG revolving credit facility contains 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 or 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 directors of CPG may similarly determine whether to declare dividends at CPG without restriction under its revolving credit agreement. At March 31, 2016 , neither CPG nor its consolidated subsidiaries had any restricted net 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 CPG. The CPG 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 . The CPG revolving credit facility also contains certain financial covenants that require CPG to maintain a consolidated total leverage ratio that does not exceed (i) 5.50 to 1.00 for any period of four consecutive fiscal quarters (each, a "test period") ending after December 31, 2015 and on or before December 31, 2017, and (ii) 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 CPG revolving credit facility), the leverage ratio may not exceed 5.50 to 1.00 . A breach of any of these covenants could result in a default in respect of the related debt. 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 CPG or any guarantor. The Merger, if completed, would constitute a change of control under the terms of the CPG revolving credit facility. Accordingly, in connection with the closing of the Merger, CPG expects the CPG revolving credit facility to be terminated and all outstanding amounts thereunder to be repaid and any existing letters of credit to be replaced. See Note 1, “Basis of Accounting Presentation” for additional information regarding the Merger. As of March 31, 2016 and December 31, 2015 , CPG had no outstanding borrowings and had $18.1 million in letters of credit under the revolving credit facility, respectively. CPPL Revolving Credit Facility. On December 5, 2014, CPPL 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 CPPL's IPO with a termination date of February 11, 2020. The credit facility is available for general partnership purposes, including working capital and capital expenditures, including the funding of capital calls. CPPL’s obligations under the revolving credit facility are unsecured. The loans thereunder bear interest at CPPL’s 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 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 CPPL's credit facility ranks equally with all CPPL’s outstanding unsecured and unsubordinated debt. CPG, CEG, OpCo GP and Columbia OpCo have each fully guaranteed CPPL's credit facility. CPPL’s revolving credit facility contains various covenants and restrictive provisions which, among other things, limit CPPL’s ability and CPPL’s restricted subsidiaries’ ability to incur additional indebtedness, guarantees and/or liens; consolidate, merge or transfer all or substantially all of CPPL’s 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 CPPL’s organizational documents. The restricted payment provision does not prohibit CPPL or 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 CPPL revolving credit agreement), and neither CPPL nor any of its restricted subsidiaries has any restrictions on its ability to make distributions under its organizational documents. In particular, in accordance with CPPL's partnership agreement, the general partner has adopted a policy that CPPL will make quarterly cash distributions in amounts equal to at least the minimum quarterly distributions 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 March 31, 2016 , neither CPPL nor its consolidated subsidiaries had any restricted net assets. If CPPL fails to perform the 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. CPPL’s revolving credit facility also contains customary events of default, including cross default provisions that apply to any other indebtedness it may have with an outstanding principal amount in excess of $50.0 million . The revolving credit facility also contains certain financial covenants that require CPPL to maintain a consolidated total leverage ratio that does not exceed (i) 5.50 to 1.00 for any test period ending after December 31, 2015, and on or before December 31, 2017, and (ii) 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 CPPL revolving credit facility), the leverage ratio shall not exceed 5.50 to 1.00 . A breach of any of these covenants could result in a default in respect of the related debt. 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 CPPL or any guarantor. The Merger, if completed, would constitute a change of control under the terms of the CPPL revolving credit facility. Accordingly, in connection with the closing of the Merger, CPG expects the CPPL revolving credit facility to be terminated and all outstanding amounts thereunder to be repaid and any existing letters of credit to be replaced. See Note 1, “Basis of Accounting Presentation” for additional information regarding the Merger. As of March 31, 2016 and December 31, 2015 , CPPL had $15.0 million in outstanding borrowings and issued no letters of credit under the revolving credit facility. CPG Commercial Paper Program. On October 5, 2015, CPG established a commercial paper program (the “Program”) pursuant to which CPG may issue short-term promissory notes (the “Promissory Notes”) pursuant to the exemption from registration contained in Section 4(a)(2) of the Securities Act of 1933, as amended (the "Securities Act"). Amounts available under the Program may be borrowed, repaid and re-borrowed from time to time, with the aggregate face or principal amount of the Promissory Notes outstanding under the Program at any time not to exceed $1,000.0 million . CEG, OpCo GP and Columbia OpCo have each agreed, jointly and severally, unconditionally and irrevocably to guarantee payment in full of the principal of and interest (if any) on the Promissory Notes. The net proceeds of issuances of the Promissory Notes are expected to be used for general corporate purposes. As of March 31, 2016 and December 31, 2015 , CPG had no Promissory Notes outstanding under the Program. Short-term borrowings were as follows: (in millions) March 31, December 31, 2015 Commercial paper borrowings $ — $ — CPG credit facility borrowings — — CPPL credit facility borrowings, weighted average interest rate of 1.50% and 1.28% at March 31, 2016 and December 31, 2015, respectively 15.0 15.0 Total Short-Term Borrowings $ 15.0 $ 15.0 Given their maturity and turnover is less than 90 days, cash flows related to the borrowings and repayments of the items listed above are presented net in the Condensed Statements of Consolidated Cash Flows (unaudited).

Long-Term Debt

Long-Term Debt	3 Months Ended
	Mar. 31, 2016
Debt Instrument [Line Items]
Long-Term Debt	Long-Term Debt Senior notes issuance. On May 22, 2015, CPG issued its private placement of $2,750.0 million in aggregated principal amount of its senior notes, comprised of $500.0 million of 2.45% senior notes due 2018 (the “2018 Notes”), $750.0 million of 3.30% senior notes due 2020 (the “2020 Notes”), $1,000.0 million of 4.50% senior notes due 2025 (the “2025 Notes”) and $500.0 million of 5.80% senior notes due 2045 (the “2045 Notes” and, together with the 2018 Notes, 2020 Notes and 2025 Notes, the “Notes”). The Notes were issued at a discount, for net proceeds of approximately $2,722.3 million after deducting the Initial Purchasers’ discount and estimated offering expenses of CPG. Indenture. The Notes are governed by an Indenture, dated as of May 22, 2015 (the “Indenture”), entered into by CPG and the certain subsidiary guarantors named therein (the "Guarantors") with U.S. Bank National Association, as trustee (the “Trustee”). The initial Guarantors are three subsidiaries of CPG, CEG, Columbia OpCo and OpCo GP. The Notes are fully and unconditionally guaranteed, jointly and severally, on a senior unsecured basis by all of the Guarantors. Each guarantee of CPG’s obligations under the Notes is a direct, unsecured and unsubordinated obligation of the applicable Guarantor and has the same ranking with respect to indebtedness of that Guarantor as the Notes have with respect to CPG’s indebtedness. The guarantees of any Guarantor may be released under certain circumstances. First, if CPG discharges or defeases its obligations with respect to the Notes of any series, then any guarantee will be released with respect to that series. Second, if no event of default has occurred and is continuing under the Indenture, a Guarantor will be automatically and unconditionally released and discharged from its guarantee (i) at any time after June 1, 2018, upon any sale, exchange or transfer, whether by way of merger or otherwise, to any person that is not CPG’s affiliate, of all of CPG’s direct or indirect limited partnership, limited liability or other equity interests in the Guarantor; (ii) upon the merger of a guarantor into CPG or any other Guarantor or the liquidation and dissolution of such Guarantor; or (iii) at any time after June 1, 2018, upon release of all guarantees or other obligations of the Guarantor with respect to any of CPG’s funded debt, except the Notes. The Indenture governing the Notes contains covenants that, among other things, limit the ability of CPG and certain of its subsidiaries to incur liens, to enter into sale and lease-back transactions and to enter into mergers, consolidations or transfers of all or substantially all of their assets. The Indenture also contains customary events of default. The 2018 Notes will mature on June 1, 2018 , the 2020 Notes will mature on June 1, 2020 , the 2025 Notes will mature on June 1, 2025 and the 2045 Notes will mature on June 1, 2045 . Interest on the Notes of each series will be payable semi-annually in arrears on June 1 and December 1, commencing on December 1, 2015. Registration Rights Agreement. In connection with the private placement of the Notes, CPG and the Guarantors entered into a Registration Rights Agreement (the “Registration Rights Agreement”) with the Initial Purchasers, pursuant to which CPG and the Guarantors agreed to file, and use their reasonable best efforts to cause to become effective, an exchange offer registration statement with the SEC and to consummate an exchange offer within 360 days after the date of issuance of the Notes pursuant to which holders of each series of the Notes can exchange the Notes issued in the offering for registered notes having the same terms as the Notes. On February 23, 2016, CPG filed an exchange offer registration statement with the SEC. The registration statement was declared effective as of April 14, 2016.

Gain on Sale of Assets

Gain on Sale of Assets	3 Months Ended
	Mar. 31, 2016
Gain On Sale of Assets [Abstract]
Gain on Sale of Assets	Gain on Sale of Assets CPG recognizes gains on conveyances of mineral rights positions into earnings as any obligation associated with conveyance is satisfied. For the three months ended March 31, 2016 and 2015 , gains on conveyances amounted to $2.6 million and $5.3 million , respectively, and are included in "Gain on sale of assets" on the Condensed Statements of Consolidated Operations (unaudited). As of March 31, 2016 and December 31, 2015 , deferred gains of approximately $5.5 million and $8.1 million , respectively, were deferred pending performance of future obligations and recorded within "Deferred revenue," on the Condensed Consolidated Balance Sheets (unaudited).

Goodwill

Goodwill	3 Months Ended
	Mar. 31, 2016
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill	Goodwill CPG 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 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 CPG's goodwill relates to NiSource's acquisition of CEG in 2000, which was contributed to CPG prior to the Separation. CPG’s goodwill assets at March 31, 2016 were $1,975.5 million . CPG's predecessor 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. CPG 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, CPG 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. CPG 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. In consideration of all relevant factors, including the recent Merger Agreement, there were no indicators that would require goodwill impairment testing during the first quarter of 2016 .

Asset Retirement Obligations

Asset Retirement Obligations	3 Months Ended
	Mar. 31, 2016
Asset Retirement Obligation [Abstract]
Asset Retirement Obligations	Asset Retirement Obligations Changes in CPG’s liability for asset retirement obligations for the three months ended March 31, 2016 and 2015 are presented in the table below: (in millions) 2016 2015 Balance as of January 1, $ 25.7 $ 23.2 Accretion expense 0.3 0.3 Additions — — Settlements — — Change in estimated cash flows (0.9 ) — Balance as of March 31, $ 25.1 $ 23.5 CPG's 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. CPG recognizes that certain assets, which include gas pipelines and natural gas storage wells, will operate for an indeterminate future period when properly maintained. A liability for these asset retirement obligations will be recorded only if and when a future retirement obligation with a determinable life is identified.

Regulatory Matters

Regulatory Matters	3 Months Ended
	Mar. 31, 2016
Regulatory Assets and Liabilities Disclosure [Abstract]
Regulatory Matters	Regulatory Matters Columbia Gas Transmission Customer Settlement. In November 2015, Columbia Gas Transmission commenced the fourth year of the Columbia Gas Transmission long-term system modernization program. Columbia Gas Transmission expects to place approximately $300 million in modernization investments into service during the year. Recovery of approximately $320 million of investments made in 2015 began on February 1, 2016. In December 2015, Columbia Gas Transmission filed an extension of this settlement and received the FERC's approval of the customer agreement in March 2016.This extension will allow Columbia Gas Transmission to invest an additional $1.1 billion over an additional three-year period through 2020. This agreement also expands the scope of facility investments covered by the program. Columbia Gulf. On January 21, 2016, the FERC issued an Order (the "January 21 Order") initiating an investigation pursuant to Section 5 of the NGA to determine whether Columbia Gulf’s existing rates for jurisdictional services are unjust and unreasonable. Columbia Gulf filed a cost and revenue study with the FERC on April 5, 2016, as required by the January 21 Order. The January 21 Order directed that a hearing be conducted pursuant to an accelerated timeline and that an initial decision be issued by February 28, 2017. The outcome of this proceeding to Columbia Gulf is not currently determinable. 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 NGA. 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	3 Months Ended
	Mar. 31, 2016
Equity Method Investments [Abstract]
Equity Method Investments	Equity Method Investments Certain investments of CPG are accounted for under the equity method of accounting. These investments are recorded within "Unconsolidated Affiliates" on CPG's Condensed Consolidated Balance Sheets (unaudited) and CPG's portion of the results is reflected in "Equity Earnings in Unconsolidated Affiliates" on CPG's Condensed Statements of Consolidated Operations (unaudited). These investments are integral to CPG’s business. Contributions are made to these equity investees to fund CPG’s share of capital projects. The following table contains contribution and distribution data representing CPG's portion based on CPG's ownership percentage of each investment: Three Months Ended (in millions) 2016 2015 Millennium Pipeline Contributions to Millennium Pipeline $ 1.9 $ — Distributions of earnings from Millennium Pipeline 15.2 16.6 Hardy Storage Contributions to Hardy Storage — — Distributions of earnings from Hardy Storage 0.7 0.5 Pennant Contributions to Pennant — — Distributions of earnings from Pennant 3.0 1.2 Return of capital from Pennant 0.2 1.3

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2016
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes CPG’s interim effective tax rates reflect the estimated annual effective tax rates for 2016 and 2015 , adjusted for tax expense associated with certain discrete items. The effective tax rates for the three months ended March 31, 2016 and 2015 were 33.0% and 34.8% , respectively. The effective tax rates for 2016 and 2015 differ 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 income received following CPPL’s IPO that is not subject to income tax at the partnership level. The effective tax rate is impacted by CPPL’s IPO which modified the ownership structure and now reflects CPPL earnings for which the noncontrolling public limited partners are directly responsible for the related income taxes. CPG consolidates the pre-tax income related to the noncontrolling public limited partners’ share of partnership earnings but excludes the related tax provision.

Pension and Other Postretiremen

Pension and Other Postretirement Benefits	3 Months Ended
	Mar. 31, 2016
Pension and Other Postretirement Benefit Expense [Abstract]
Pension and Other Postretirement Benefits	Pension and Other Postretirement Benefits CPG provides defined contribution plans and noncontributory defined benefit retirement plans that cover its employees. Benefits under the defined benefit retirement plans reflect the employees’ compensation, years of service and age at retirement. Additionally, CPG provides health care and life insurance benefits for certain retired employees. The majority of employees may become eligible for these benefits if they reach retirement age while working for CPG. The expected cost of such benefits is accrued during the employees’ years of service. Current rates charged to customers of CPG include postretirement benefit costs. Cash contributions are remitted to grantor trusts. Prior to the Separation, CPG was a participant in the consolidated NiSource defined benefit retirement plans and was allocated a ratable portion of NiSource’s grantor trusts for the plans in which its employees and retirees participated. As a result, CPG followed multiple employer accounting under the provisions of GAAP. CPG continues to follow multiple employer accounting following the Separation. The following table provides the components of CPG's net periodic benefits cost for the three months ended March 31, 2016 and 2015 : Pension Benefits Other Postretirement Three Months Ended March 31, (in millions) 2016 2015 2016 2015 Components of Net Periodic Benefit Cost (Income) Service cost $ 1.6 $ 1.3 $ 0.2 $ 0.3 Interest cost 3.9 3.5 1.2 1.2 Expected return on assets (6.7 ) (7.0 ) (4.0 ) (4.6 ) Amortization of prior service credit (0.3 ) (0.3 ) (0.2 ) (0.2 ) Recognized actuarial loss 3.1 2.4 — — Total Net Periodic Benefit Cost (Income) $ 1.6 $ (0.1 ) $ (2.8 ) $ (3.3 )

Fair Value

Fair Value	3 Months Ended
	Mar. 31, 2016
Fair Value Disclosures [Abstract]
Fair Value	Fair Value CPG 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 and short-term borrowings. CPG's long-term debt 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. The fair value of these securities is 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 three months ended March 31, 2016 and for the year ended December 31, 2015 , 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 March 31, 2016 (1) Estimated Fair Value as of March 31, 2016 Carrying Amount as of December 31, 2015 (1) Estimated Fair Value as of December 31, 2015 Long-term debt $ 2,750.0 $ 2,732.2 $ 2,750.0 $ 2,592.1 (1) The carrying amount of the Notes differs from the Long-term debt balance on the Condensed Consolidated Balance Sheets (unaudited) due to the related unamortized discount and unamortized debt issuance costs, both of which are being amortized over the weighted average life of the Notes.

Share-Based Compensation

Share-Based Compensation	3 Months Ended
	Mar. 31, 2016
Share-based Compensation [Abstract]
Share-Based Compensation	Share-Based Compensation Prior to the Separation, CPG employees participated in NiSource's Omnibus Incentive Plan (the "NiSource Plan") and had outstanding awards under the NiSource Director Stock Incentive Plan (“NiSource Director Plan”), which was terminated in 2010. Upon the Separation, outstanding CPG employee restricted stock units, performance units and non-employee director awards previously issued under the NiSource Plan and NiSource Director Plan were adjusted and converted into new CPG share-based awards under the Columbia Pipeline Group, Inc. 2015 Omnibus Incentive Plan (the "Omnibus Plan") using a formula designed to preserve the intrinsic value and fair value of the awards immediately prior to the Separation. The performance targets applicable to the performance units were frozen at the levels achieved as of the Separation and pro-rated to reflect the proportion of the service period completed. Under the Omnibus Plan, these awards represent restricted stock units with no performance contingencies. All adjusted awards retained the vesting schedule of the original awards. The Omnibus Plan term began on the effective date of the Separation. The Omnibus Plan provides for awards to employees and non-employee directors of incentive and nonqualified stock options, stock appreciation rights, restricted stock and restricted stock units, performance shares, performance units, cash-based awards and other stock-based awards. The Omnibus Plan provides that the number of shares of common stock of CPG available for awards is 8,000,000 . At March 31, 2016 , there were 4,227,203 shares reserved for future awards under the Omnibus Plan. CPG recognized stock-based employee compensation expense of $3.8 million and $1.8 million during the three months ended March 31, 2016 and 2015 , respectively, as well as related tax benefits of $1.4 million and $0.6 million , respectively. As of March 31, 2016 , the total remaining unrecognized compensation cost related to nonvested awards amounted to $33.2 million , which will be amortized over the weighted-average remaining requisite service period of 2.4 years. Restricted Stock Units and Restricted Stock . During the three months ended March 31, 2016 , CPG granted 12,144 restricted stock units and shares of restricted stock, subject to service conditions. The total grant date fair-value of the shares of restricted stock units and shares of restricted stock was $0.2 million , based on the average market price of CPG’s common stock at the date of each grant less the present value of any dividends not received during the vesting period, which will be expensed, net of forfeitures, over the vesting period which is generally three years. As of March 31, 2016 , 1,373,018 nonvested (all of which are expected to vest) restricted stock units and shares of restricted stock were granted and outstanding. Performance Shares . During the three months ended March 31, 2016 , CPG granted 995,848 performance shares, subject to performance and service conditions. The grant date fair-value of the awards was $17.0 million , based on the average market price of CPG’s common stock at the date of grant less the present value of dividends not received during the vesting period which will be expensed, net of forfeitures, over the three year requisite service period. The performance conditions are based on achievement of relative total shareholder return, Adjusted EBITDA and CPPL Distributable Cash Flow. Relative total shareholder return is a non-GAAP market measure that CPG defines as the annualized growth in the dividends and share price of a share of CPG’s common stock (calculated using a 20 trading day average of CPG’s closing price, over a period beginning January 1, 2016 and ending on December 31, 2018) compared to the total shareholder return performance of a predetermined peer group of companies. Adjusted EBITDA is a non-GAAP performance measure that CPG defines as net income before interest expense, income taxes, and depreciation and amortization, plus distributions of earnings received from equity investees, less equity earnings in unconsolidated affiliates and other, net. In addition, to the extent transactions occur that are considered unusual, infrequent or not representative of underlying trends, we will remove the effect of these items from Adjusted EBITDA. Examples of these transactions include impairments, costs associated with the Separation and costs associated with the Merger. CPPL Distributable Cash Flow is a non-GAAP performance measure that CPG defines as Adjusted EBITDA less interest expense, maintenance capital expenditures, gain on sale of assets and distributable cash flow attributable to noncontrolling interest plus proceeds from the sale of assets, interest income, capital costs related to the Separation and any other known differences between cash and income. The service conditions lapse on February 28, 2019 when the shares vest provided the performance criteria are satisfied. As of March 31, 2016 , 1,117,352 nonvested performance shares were granted and outstanding. Non-employee Director Awards . Currently, restricted stock units are granted annually to non-employee directors, subject to a non-employee director’s election to defer receipt of such restricted stock unit award. The non-employee director’s restricted stock units vest on the first anniversary of the grant thereof subject to special pro-rata vesting rules in the event of Retirement or Disability (as defined in the award agreement), or death. The vested restricted stock units are payable as soon as practicable following vesting except as otherwise provided pursuant to the non-employee director’s election to defer. As of March 31, 2016 , a total of 52,427 units are outstanding to non-employee directors under the Omnibus Plan. Of these awards, 13,495 were granted under the NiSource Plan and converted into 21,399 CPG units, while the remaining 31,028 were granted by CPG subsequent to the Separation. Fully vested restricted stock units that remained outstanding under the NiSource Plan and NiSource Director Plan as of the Separation date were converted into CPG awards. All such awards shall be distributed to the directors upon their separation from CPG's board of directors or such later date as elected. As of March 31, 2016 , 228,619 restricted stock units remain outstanding. 401(k) Match, Profit Sharing and Company Contribution. CPG has a voluntary 401(k) savings plan covering eligible employees that allows for periodic discretionary matches as a percentage of each participant’s contributions. CPG also has a retirement savings plan that provides for discretionary profit sharing contributions to eligible employees based on earnings results; and eligible exempt employees hired after January 1, 2010, receive a non-elective company contribution of three percent of eligible pay. For the three months ended March 31, 2016 and 2015 , CPG recognized 401(k) match, profit sharing and non-elective contribution expense of $3.2 million and $1.7 million , respectively.

Other Commitments and Contingen

Other Commitments and Contingencies	3 Months Ended
	Mar. 31, 2016
Commitments and Contingencies Disclosure [Abstract]
Other Commitments and Contingencies	Other Commitments and Contingencies A. Guarantees and Indemnities. In the normal course of its business, CPG and certain subsidiaries enter into various agreements providing financial or performance assurance to third parties on behalf of 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 a parent or subsidiary on a stand-alone basis, thereby facilitating the extension of sufficient credit to accomplish the parent or subsidiaries' intended commercial purposes. The total guarantees and indemnities in existence at March 31, 2016 and the years in which they expire were: (in millions) Total 2016 2017 2018 2019 2020 After Letters of credit $ 18.1 $ 18.1 $ — $ — $ — $ — $ — Other guarantees 45.6 0.6 2.0 — — — 43.0 Total commercial commitments $ 63.7 $ 18.7 $ 2.0 $ — $ — $ — $ 43.0 Guarantees of Debt. Certain of CPG's subsidiaries, including OpCo GP, Columbia OpCo and CEG have guaranteed payment of $2,750.0 million in aggregated principal amount of CPG's senior notes. Each guarantor 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. CPG does not anticipate its subsidiaries will have any difficulty maintaining compliance. Lines and Letters of Credit. CPG maintains a $1,500.0 million senior revolving credit facility, of which $250.0 million in letters of credit is available. CPG expects that $750.0 million of this facility will be utilized as credit support for Columbia OpCo and its subsidiaries and the remaining $750.0 million of this facility will be available for CPG’s general corporate purposes, including working capital. The revolving credit facility will provide liquidity support for CPG's $1,000.0 million commercial paper program. As of March 31, 2016 , CPG had no borrowings outstanding and $18.1 million in letters of credit outstanding under its revolving credit facility. CPPL 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 March 31, 2016 , CPPL had $15.0 million in outstanding borrowings and no letters of credit under its revolving credit facility. CPG has established a commercial paper program (the “Program”) pursuant to which CPG may issue short-term promissory notes (the “Promissory Notes”) pursuant to the exemption from registration contained in Section 4(a)(2) of the Securities Act of 1933, as amended (the "Securities Act"). Amounts available under the Program may be borrowed, repaid and re-borrowed from time to time, with the aggregate face or principal amount of the Promissory Notes outstanding under the Program at any time not to exceed $1,000.0 million . CEG, OpCo GP and Columbia OpCo have each agreed, jointly and severally, unconditionally and irrevocably to guarantee payment in full of the principal of and interest (if any) on the Promissory Notes. The net proceeds of issuances of the Promissory Notes are expected to be used for general corporate purposes. As of March 31, 2016 , CPG had no Promissory Notes outstanding under the Program. Other Guarantees or Obligations. CPG has purchase and sale agreement guarantees totaling $45.6 million , which guarantee purchaser performance or seller performance under covenants, obligations, liabilities, representations or warranties under the agreements. No amounts related to the purchase and sale agreement guarantees are reflected in the Condensed Consolidated Balance Sheets (unaudited). Management believes that the likelihood CPG would be required to perform or otherwise incur any significant losses associated with any of the aforementioned guarantees is remote. CPG has on deposit a letter of credit with MUFG Union Bank, N.A., Collateral Agent, in a debt service reserve account in association with Millennium Pipeline's notes as required under the Deposit and Disbursement Agreement that governs the Millennium Pipeline notes. This account is to be drawn upon by the note holders in the event that Millennium Pipeline is delinquent on its principal and interest payments. The value of CPG’s letter of credit represents 47.5% (CPG’s ownership interest in Millennium Pipeline) of the debt service reserve account requirement, or $16.2 million . The total exposure for CPG is $16.2 million . CPG has an accrued liability of $1.5 million related to the inception date fair value of this guarantee as of March 31, 2016 . B. Other Legal Proceedings. In the normal course of its business, CPG has been named as a defendant in various legal proceedings. In the opinion of CPG, the ultimate disposition of these currently asserted claims will not have a material impact on CPG’s condensed consolidated financial statements. C. Environmental Matters. CPG’s operations are subject to environmental statutes and regulations related to air quality, water quality, hazardous waste and solid waste. CPG believes that it is in substantial compliance with those environmental regulations currently applicable to its operations and believes that it has all necessary material permits to conduct its operations. It is CPG’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 CPG will not incur fines and penalties. As of March 31, 2016 and December 31, 2015 , CPG had liabilities recorded of approximately $8.2 million and $8.3 million , respectively, to cover environmental remediation at various sites. The current portion of these liabilities is included in “Other accruals” in the Condensed Consolidated Balance Sheets (unaudited). The noncurrent portion is included in “Other noncurrent liabilities” in the Condensed Consolidated Balance Sheets (unaudited). CPG accrues for costs associated with environmental remediation obligations when the incurrence of such costs is probable and the amounts can be reasonably estimated. The original estimates for cleanup can differ materially from the amount ultimately expended. The actual future expenditures depend on many factors, including currently enacted laws and regulations, the nature and extent of contamination, the method of cleanup, and the availability of cost recovery from customers. As of the date of these financial statements, these expenditures are not estimable at some sites. CPG periodically adjusts its accrual as information is collected and estimates become more refined. Air The CAA and comparable state laws regulate emissions of air pollutants from various industrial sources, including compressor stations, and also impose various monitoring and reporting requirements. Such laws and regulations may require pre-approval for the construction or modification of certain projects or facilities expected to produce air emissions or result in an increase of existing air emissions; application for, and strict compliance with, air permits containing various emissions and operational limitations; or the utilization of specific emission control technologies to limit emissions. The actions listed below could require further reductions in emissions from various emission sources. CPG will continue to closely monitor developments in these matters. National Ambient Air Quality Standards . The federal 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 gas transmission operations. The following NAAQS were recently added or modified: Ozone : On October 1, 2015, the EPA issued a final rule lowering the NAAQS for ground-level ozone to 70 ppb under both the primary and secondary standards to provide requisite protection of public health and welfare, respectively. The EPA is required to include an adequate margin of safety in establishing the primary ozone standard for protection of public health, whereas the secondary ozone standard is intended to improve protection for trees, plants and ecosystems. The final rule becomes effective sixty days after the rule is published in the Federal Register. The EPA is required to make attainment and non-attainment designations for specific geographic locations under the revised standards by October 1, 2017 and, depending on the severity of the ozone present, non-attainment areas will have until between 2020 and 2037 to meet the health standard. With the EPA lowering the ground-level ozone standard, states may be required to implement more stringent regulations. Based on the current version of the rule, CPG does not expect a material impact on its operations. 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 CPG 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 CPG combustion sources may need to be assessed and mitigated. CPG will continue to monitor this matter and cannot estimate the impact of these rules at this time. Climate Change. Future legislative and regulatory programs could significantly restrict emissions of greenhouse gases including methane. New Source Performance Standards : On August 18, 2015, the EPA proposed to regulate fugitive methane emissions for compressor stations in the natural gas transmission and storage sector. The proposed rule was subsequently published in the Federal Register on September 18, 2015. Semiannual leak detection and repair requirements using optical gas imaging are proposed for all components at new or existing compressor stations. Existing compressor stations trigger leak detection and repair requirements if any unit at the facility is modified. The EPA proposed additional requirements for any new or modified centrifugal or reciprocating compressors. Replacement of wet seals with dry seals or demonstrating a 95% reduction of methane emissions from wet seals is proposed for centrifugal compressors and rod packing replacement for reciprocating compressors is proposed every 26,000 hours of operation or every three years. CPG will continue to monitor this matter and cannot estimate the impact of these rules at this time. Pipeline Safety On March 17, 2016, the federal Pipeline and Hazardous Materials Safety Administration (“PHMSA”) announced a proposed rulemaking that would, if adopted, impose more stringent requirements for certain gas lines and gathering lines under varying circumstances. Among other things, the proposed rulemaking would extend certain of PHMSA’s current regulatory safety programs for gas pipelines beyond “high consequence areas” to cover gas pipelines found in newly defined “moderate consequence areas” that contain as few as 5 dwellings within the potential impact area; require gas pipelines installed before 1970 that are currently exempted from certain pressure testing obligations to be tested to determine their maximum allowable operating pressures (“MAOP”); and require gathering lines in Class I areas, both onshore and offshore, to comply with standards regarding damage prevention, corrosion control (for metallic pipe), public education, MAOP limits, line markers and emergency planning if such gathering lines’ nominal design is 8 inches or more. In order to provide clarity and greater certainty on what may constitute a “gathering line,” PHMSA is proposing a new definition of that term under the rulemaking, which term would now encompass “a pipeline, or a connected series of pipelines, and equipment used to collect gas from the endpoint of a production facility/operation and transport it to the furthermost point downstream of the following endpoints” including the “inlet of 1 st gas processing plant;” the “outlet of” a gas treatment facility (not associated with a processing plant or compressor station); the “[o]utlet of the furthermost downstream compressor” leading to a pipeline, or the “point where separate production fields are commingled.” Other new requirements proposed by PHMSA under the rulemaking would require pipeline operators to: report to PHMSA in the event of certain MAOP exceedances; strengthen PHMSA integrity management requirements; consider seismicity in evaluating threats to a pipeline; conduct hydrostatic testing for all pipeline segments manufactured using longitudinal seam welds; and use more detailed guidance from PHMSA in the selection of assessment methods to inspect pipelines. Adoption of some or all of these standards under the proposed rulemaking could cause us to incur increased capital costs and costs of operation, which could be significant. Waste CPG has liabilities associated with the cleanup of some of its former operations. Four sites are associated with its former propane operations and ten sites associated with former petroleum operations. The total liability related to these sites was $6.4 million and $6.5 million at March 31, 2016 and December 31, 2015 , respectively. The liability represents CPG’s best estimate of the cost to remediate the facilities. CPG has liabilities associated with the PCB remediation of its existing facilities. The total liability related to these sites was $1.8 million at March 31, 2016 and December 31, 2015 . The liability represents CPG's best estimate of the cost to remediate the facilities.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Loss	3 Months Ended
	Mar. 31, 2016
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 months ended March 31, 2016 and 2015 : Three Months Ended March 31, 2016 (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, 2016 $ (14.3 ) $ (12.7 ) $ (27.0 ) Other comprehensive income before reclassifications — 0.1 0.1 Amounts reclassified from accumulated other comprehensive income 0.4 — 0.4 Net current-period other comprehensive income 0.4 0.1 0.5 Allocation of accumulated other comprehensive loss to noncontrolling interest 0.1 — 0.1 Balance as of March 31, 2016 $ (14.0 ) $ (12.6 ) $ (26.6 ) (1) All amounts are net of tax. Amounts in parentheses indicate debits. Three Months Ended March 31, 2015 (in millions) Gains and Losses on Cash Flow Hedges (1) Pension and OPEB Items (1) Accumulated (1) Balance as of January 1, 2015 $ (16.6 ) $ (17.9 ) $ (34.5 ) Other comprehensive income before reclassifications — 6.9 6.9 Amounts reclassified from accumulated other comprehensive income 0.2 0.1 0.3 Net current-period other comprehensive income 0.2 7.0 7.2 Allocation of accumulated other comprehensive loss to noncontrolling interest 2.2 — 2.2 Balance as of March 31, 2015 $ (14.2 ) $ (10.9 ) $ (25.1 ) (1) All amounts are net of tax. Amounts in parentheses indicate debits. Equity Investment Millennium Pipeline is an equity method investment, and, therefore, CPG is required to recognize a proportional share of Millennium Pipeline’s OCI. The remaining unrecognized loss at March 31, 2016 of $14.0 million , after tax, related to terminated interest rate swaps is being amortized over a 15 year 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 $14.0 million and $14.3 million , after tax, at March 31, 2016 and December 31, 2015 , respectively, is included in gains and losses on cash flow hedges above.

Other, Net

Other, Net	3 Months Ended
	Mar. 31, 2016
Other Income and Expenses [Abstract]
Other, Net	Other, Net Three Months Ended (in millions) 2016 2015 AFUDC Equity $ 6.1 $ 3.5 Miscellaneous 0.9 1.1 Total Other, net $ 7.0 $ 4.6

Supplemental Cash Flow Informat

Supplemental Cash Flow Information	3 Months Ended
	Mar. 31, 2016
Supplemental Cash Flow Information [Abstract]
Supplemental Cash Flow Information	Supplemental Cash Flow Information The following table provides additional information regarding CPG’s Condensed Statements of Consolidated Cash Flows (unaudited) for the three months ended March 31, 2016 and 2015 : (in millions) 2016 2015 Supplemental Disclosures of Cash Flow Information Non-cash transactions: Capital expenditures included in current liabilities (1) $ 120.7 $ 98.8 Schedule of interest and income taxes paid: Cash paid for interest, net of interest capitalized amounts $ 6.2 $ 15.6 Cash paid for income taxes 1.1 9.4 (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 Balance Sheets (unaudited).

Concentration of Credit Risk

Concentration of Credit Risk	3 Months Ended
	Mar. 31, 2016
Risks and Uncertainties [Abstract]
Concentration Risk Disclosure	Concentration of Credit Risk Columbia Gas of Ohio, an affiliated party prior to the Separation, accounted for greater than 10% of total operating revenues for the three months ended March 31, 2016 and 2015 . The following tables provide this customer's operating revenues and percentage of total operating revenues for the three months ended March 31, 2016 and 2015 : Three Months Ended March 31, 2016 2015 (in millions) Total Operating Revenues Percentage of Total Operating Revenues Total Operating Revenues Percentage of Total Operating Revenues Columbia Gas of Ohio (1) $ 50.4 13.8 % $ 48.9 14.4 % (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 CPG receives from Columbia Gas of Ohio in any given period. The loss of a significant portion of operating revenues from this customer could have a material adverse effect on the business of CPG.

Condensed Consolidating Financi

Condensed Consolidating Financial Statements	3 Months Ended
	Mar. 31, 2016
Guarantees [Abstract]
Condensed Consolidating Financial Statements	Condensed Consolidating Financial Information On May 22, 2015, CPG closed its private placement of $2,750.0 million in aggregated principal amount of its senior notes (the "Notes"). Please see Note 7, "Long-Term Debt" for further discussion of the Notes. The Notes are fully and unconditionally guaranteed, jointly and severally, on a senior unsecured basis by three of CPG's subsidiaries, CEG, Columbia OpCo and OpCo GP. CEG is a 100% owned subsidiary of CPG. In lieu of providing separate financial statements for CEG, the accompanying condensed consolidating financial statements based on Rule 3-10 of the SEC’s Regulation S-X have been included. The following supplemental condensed consolidating financial information reflects CPG’s separate accounts, the combined accounts of CEG and Other Subsidiaries of CEG and CPG, including guarantors Columbia OpCo and OpCo GP, the consolidating adjustments and eliminations and the Issuer’s consolidated accounts for the dates and periods indicated. Separate financial statements have been provided for Columbia OpCo and OpCo GP based on Rule 3-10 of the SEC's Regulation S-X. For purposes of the following consolidating information, CPG’s and CEG's investment in its subsidiaries is accounted for under the equity method of accounting. CONDENSED CONSOLIDATING BALANCE SHEETS As of March 31, 2016 (in millions) CPG CEG Columbia OpCo OpCo GP Non-guarantor Subsidiaries Consolidating adjustments and eliminations CPG Consolidated ASSETS Current Assets Cash and cash equivalents $ 549.2 $ 53.8 $ — $ — $ 37.9 $ — $ 640.9 Accounts receivable, net 0.5 5.6 — — 155.4 — 161.5 Accounts receivable-affiliated 105.4 193.4 — — 135.5 (434.3 ) — Materials and supplies, at average cost — — — — 33.2 — 33.2 Exchange gas receivable — — — — 12.0 — 12.0 Deferred property taxes — — — — 54.2 — 54.2 Prepayments and other 9.3 4.6 — — 41.9 (9.3 ) 46.5 Total Current Assets 664.4 257.4 — — 470.1 (443.6 ) 948.3 Investments Unconsolidated affiliates — — — — 437.3 — 437.3 Consolidated affiliates 5,278.9 7,624.1 5,791.0 — — (18,694.0 ) — Other investments 12.0 0.3 — — 1.5 — 13.8 Total Investments 5,290.9 7,624.4 5,791.0 — 438.8 (18,694.0 ) 451.1 Property, Plant and Equipment Property, plant and equipment — — — — 9,426.0 — 9,426.0 Accumulated depreciation and amortization — — — — (3,025.1 ) — (3,025.1 ) Net Property, Plant and Equipment — — — — 6,400.9 — 6,400.9 Other Noncurrent Assets Regulatory assets — 41.1 — — 141.1 — 182.2 Goodwill — — 1,975.5 — — — 1,975.5 Notes receivable-affiliated 1,848.2 — — — — (1,848.2 ) — Postretirement and postemployment benefits assets — 0.6 — — 117.5 (0.4 ) 117.7 Deferred income taxes 23.3 — — — — (23.3 ) — Deferred charges and other 4.6 — — — 10.8 — 15.4 Total Other Noncurrent Assets 1,876.1 41.7 1,975.5 — 269.4 (1,871.9 ) 2,290.8 Total Assets $ 7,831.4 $ 7,923.5 $ 7,766.5 $ — $ 7,579.2 $ (21,009.5 ) $ 10,091.1 CONDENSED CONSOLIDATING BALANCE SHEETS (continued) As of March 31, 2016 (in millions) CPG CEG Columbia OpCo OpCo GP Non-guarantor Subsidiaries Consolidating adjustments and eliminations CPG Consolidated LIABILITIES AND EQUITY Current Liabilities Short-term borrowings $ — $ — $ — $ — $ 15.0 $ — $ 15.0 Short-term borrowings-affiliated — — 124.0 — 283.9 (407.9 ) — Accounts payable 11.0 — — — 47.7 — 58.7 Accounts payable-affiliated 7.8 14.9 0.1 — 3.6 (26.4 ) — Dividends payable 53.6 — — — — — 53.6 Customer deposits — — — — 18.8 — 18.8 Taxes accrued — 10.6 — — 99.7 (9.3 ) 101.0 Interest accrued 37.0 — — — 0.2 — 37.2 Exchange gas payable — — — — 12.1 — 12.1 Deferred revenue — — — — 10.5 — 10.5 Accrued capital expenditures — — — — 88.7 — 88.7 Accrued compensation and related costs — — — — 28.5 — 28.5 Other accruals 0.3 0.3 — — 89.3 — 89.9 Total Current Liabilities 109.7 25.8 124.1 — 698.0 (443.6 ) 514.0 Noncurrent Liabilities Long-term debt 2,725.9 — — — — — 2,725.9 Long-term debt-affiliated — 1,217.3 — — 630.9 (1,848.2 ) — Deferred income taxes — 1,396.7 — — 21.9 (23.3 ) 1,395.3 Accrued liability for postretirement and postemployment benefits 0.3 7.8 — — 41.2 (0.4 ) 48.9 Regulatory liabilities — 10.4 — — 293.2 — 303.6 Asset retirement obligations — — — — 25.1 — 25.1 Other noncurrent liabilities 11.6 0.3 — — 82.5 — 94.4 Total Noncurrent Liabilities 2,737.8 2,632.5 — — 1,094.8 (1,871.9 ) 4,593.2 Total Liabilities 2,847.5 2,658.3 124.1 — 1,792.8 (2,315.5 ) 5,107.2 Equity Common stock 4.0 — — — — — 4.0 Additional paid-in capital 4,037.1 — — — — — 4,037.1 Retained earnings 14.0 — — — — — 14.0 Net parent investment — 4,330.2 7,667.3 — 5,815.4 (17,812.9 ) — Treasury stock (6.0 ) — — — — — (6.0 ) Accumulated other comprehensive loss (26.6 ) (26.4 ) (24.9 ) — (29.0 ) 80.3 (26.6 ) Total CPG Equity 4,022.5 4,303.8 7,642.4 — 5,786.4 (17,732.6 ) 4,022.5 Noncontrolling Interest 961.4 961.4 — — — (961.4 ) 961.4 Total Equity 4,983.9 5,265.2 7,642.4 — 5,786.4 (18,694.0 ) 4,983.9 Total Liabilities and Equity $ 7,831.4 $ 7,923.5 $ 7,766.5 $ — $ 7,579.2 $ (21,009.5 ) $ 10,091.1 CONDENSED CONSOLIDATING BALANCE SHEETS (continued) As of December 31, 2015 (in millions) CPG CEG Columbia OpCo OpCo GP Non-guarantor Subsidiaries Consolidating adjustments and eliminations CPG Consolidated ASSETS Current Assets Cash and cash equivalents $ 800.0 $ 46.7 $ 1.9 $ — $ 82.3 $ — $ 930.9 Accounts receivable, net — 5.6 — — 146.8 — 152.4 Accounts receivable-affiliated 14.6 85.6 3.4 — 156.4 (260.0 ) — Materials and supplies, at average cost — — — — 32.8 — 32.8 Exchange gas receivable — — — — 19.0 — 19.0 Deferred property taxes — — — — 52.0 — 52.0 Prepayments and other 0.3 10.1 — — 43.8 (5.7 ) 48.5 Total Current Assets 814.9 148.0 5.3 — 533.1 (265.7 ) 1,235.6 Investments Unconsolidated affiliates — — — — 438.1 — 438.1 Consolidated affiliates 5,174.6 7,569.8 5,608.9 — — (18,353.3 ) — Other investments 12.0 0.3 — — 1.5 — 13.8 Total Investments 5,186.6 7,570.1 5,608.9 — 439.6 (18,353.3 ) 451.9 Property, Plant and Equipment Property, plant and equipment — — — — 9,052.3 — 9,052.3 Accumulated depreciation and amortization — — — — (2,988.6 ) — (2,988.6 ) Net Property, Plant and Equipment — — — — 6,063.7 — 6,063.7 Other Noncurrent Assets Regulatory assets — 35.1 — — 142.6 — 177.7 Goodwill — — 1,975.5 — — — 1,975.5 Notes receivable-affiliated 1,848.2 — — — — (1,848.2 ) — Postretirement and postemployment benefits assets — 0.5 — — 115.6 (0.4 ) 115.7 Deferred income taxes 18.9 — — — — (18.9 ) — Deferred charges and other 4.9 — — — 10.6 — 15.5 Total Other Noncurrent Assets 1,872.0 35.6 1,975.5 — 268.8 (1,867.5 ) 2,284.4 Total Assets $ 7,873.5 $ 7,753.7 $ 7,589.7 $ — $ 7,305.2 $ (20,486.5 ) $ 10,035.6 CONDENSED CONSOLIDATING BALANCE SHEETS (continued) As of December 31, 2015 (in millions) CPG CEG Columbia OpCo OpCo GP Non-guarantor Subsidiaries Consolidating adjustments and eliminations CPG Consolidated LIABILITIES AND EQUITY Current Liabilities Short-term borrowings $ — $ — $ — $ — $ 15.0 $ — $ 15.0 Short-term borrowings-affiliated 99.0 — — — 134.3 (233.3 ) — Accounts payable 0.1 — — — 56.7 — 56.8 Accounts payable-affiliated 10.8 4.8 — — 11.1 (26.7 ) — Customer deposits — — — — 17.9 — 17.9 Taxes accrued — — — — 111.7 (5.7 ) 106.0 Interest accrued 9.4 — — — 0.1 — 9.5 Exchange gas payable — — — — 18.6 — 18.6 Deferred revenue — — — — 15.0 — 15.0 Accrued capital expenditures — — — — 100.1 — 100.1 Accrued compensation and related costs — — — — 51.9 — 51.9 Other accruals — 0.3 — — 69.7 — 70.0 Total Current Liabilities 119.3 5.1 — — 602.1 (265.7 ) 460.8 Noncurrent Liabilities Long-term debt 2,725.6 — — — — — 2,725.6 Long-term debt-affiliated — 1,217.3 — — 630.9 (1,848.2 ) — Deferred income taxes — 1,350.4 — — 16.6 (18.9 ) 1,348.1 Accrued liability for postretirement and postemployment benefits 0.3 8.3 — — 41.2 (0.4 ) 49.4 Regulatory liabilities — 10.5 — — 311.1 — 321.6 Asset retirement obligations — — — — 25.7 — 25.7 Other noncurrent liabilities 15.3 0.2 — — 75.9 — 91.4 Total Noncurrent Liabilities 2,741.2 2,586.7 — — 1,101.4 (1,867.5 ) 4,561.8 Total Liabilities 2,860.5 2,591.8 — — 1,703.5 (2,133.2 ) 5,022.6 Equity Common stock 4.0 — — — — — 4.0 Additional paid-in capital 4,032.7 — — — — — 4,032.7 Retained earnings 46.9 — — — — — 46.9 Net parent investment — 4,232.3 7,615.4 — 5,631.3 (17,479.0 ) — Accumulated other comprehensive loss (27.0 ) (26.8 ) (25.7 ) — (29.6 ) 82.1 (27.0 ) Total CPG Equity 4,056.6 4,205.5 7,589.7 — 5,601.7 (17,396.9 ) 4,056.6 Noncontrolling Interest 956.4 956.4 — — — (956.4 ) 956.4 Total Equity 5,013.0 5,161.9 7,589.7 — 5,601.7 (18,353.3 ) 5,013.0 Total Liabilities and Equity $ 7,873.5 $ 7,753.7 $ 7,589.7 $ — $ 7,305.2 $ (20,486.5 ) $ 10,035.6 CONDENSED CONSOLIDATING STATEMENTS OF OPERATIONS Three Months Ended March 31, 2016 (in millions) CPG CEG Columbia OpCo OpCo GP Non-guarantor Subsidiaries Consolidating adjustments and eliminations CPG Consolidated Operating Revenues Transportation revenues $ — $ — $ — $ — $ 308.5 $ — $ 308.5 Transportation revenues-affiliated — — — — — — — Storage revenues — — — — 49.9 — 49.9 Storage revenues-affiliated — — — — — — — Other revenues — — — — 6.1 — 6.1 Total Operating Revenues — — — — 364.5 — 364.5 Operating Expenses Operation and maintenance 30.4 (0.2 ) — — 139.1 (0.2 ) 169.1 Operation and maintenance-affiliated 0.1 — — — — (0.1 ) — Depreciation and amortization — 0.2 — — 40.2 — 40.4 Gain on sale of assets — — — — (2.6 ) — (2.6 ) Property and other taxes 0.1 — — — 21.7 — 21.8 Total Operating Expenses 30.6 — — — 198.4 (0.3 ) 228.7 Equity Earnings in Unconsolidated Affiliates — — — — 15.9 — 15.9 Equity Earnings in Consolidated Affiliates 113.5 179.8 181.5 — — (474.8 ) — Operating Income 82.9 179.8 181.5 — 182.0 (474.5 ) 151.7 Other Income (Deductions) Interest expense (29.5 ) — — — (0.6 ) 0.7 (29.4 ) Interest expense-affiliated — (11.2 ) (0.1 ) — (7.2 ) 18.5 — Other, net 19.7 0.5 — — 6.0 (19.2 ) 7.0 Total Other Deductions, net (9.8 ) (10.7 ) (0.1 ) — (1.8 ) — (22.4 ) Income from Continuing Operations before Income Taxes 73.1 169.1 181.4 — 180.2 (474.5 ) 129.3 Income Taxes (13.5 ) 56.8 — — 0.5 (1.1 ) 42.7 Income from Continuing Operations 86.6 112.3 181.4 — 179.7 (473.4 ) 86.6 Income from Discontinued Operations-net of taxes 0.2 0.2 — — — (0.2 ) 0.2 Net Income 86.8 112.5 181.4 — 179.7 (473.6 ) 86.8 Less: Net income attributable to noncontrolling interest 14.6 14.6 — — — (14.6 ) 14.6 Net Income Attributable to CPG $ 72.2 $ 97.9 $ 181.4 $ — $ 179.7 $ (459.0 ) $ 72.2 CONDENSED CONSOLIDATING STATEMENTS OF OPERATIONS (continued) Three Months Ended March 31, 2015 (in millions) CPG CEG Columbia OpCo OpCo GP Non-guarantor Subsidiaries Consolidating adjustments and eliminations CPG Consolidated Operating Revenues Transportation revenues $ — $ — $ — $ — $ 248.4 $ — $ 248.4 Transportation revenues-affiliated — — — — 29.0 — 29.0 Storage revenues — — — — 36.6 — 36.6 Storage revenues-affiliated — — — — 13.3 — 13.3 Other revenues — — — — 12.7 — 12.7 Total Operating Revenues — — — — 340.0 — 340.0 Operating Expenses Operation and maintenance — (0.1 ) — — 118.5 — 118.4 Operation and maintenance-affiliated — 0.1 — — 27.9 — 28.0 Depreciation and amortization — — — — 32.5 — 32.5 Gain on sale of assets — — — — (5.3 ) — (5.3 ) Property and other taxes — — — — 19.1 — 19.1 Total Operating Expenses — — — — 192.7 — 192.7 Equity Earnings in Unconsolidated Affiliates — — — — 15.4 — 15.4 Equity Earnings in Consolidated Affiliates 97.1 131.2 131.2 — — (359.5 ) — Operating Income 97.1 131.2 131.2 — 162.7 (359.5 ) 162.7 Other Income (Deductions) Interest expense-affiliated — (6.9 ) — — (11.4 ) — (18.3 ) Other, net — 0.4 0.7 — 3.5 — 4.6 Total Other Deductions, net — (6.5 ) 0.7 — (7.9 ) — (13.7 ) Income before Income Taxes 97.1 124.7 131.9 — 154.8 (359.5 ) 149.0 Income Taxes — 27.6 — — 24.3 — 51.9 Net Income 97.1 97.1 131.9 — 130.5 (359.5 ) 97.1 Less: Net income attributable to noncontrolling interest 7.1 7.1 — — — (7.1 ) 7.1 Net Income Attributable to CPG $ 90.0 $ 90.0 $ 131.9 $ — $ 130.5 $ (352.4 ) $ 90.0 CONDENSED CONSOLIDATING STATEMENTS OF COMPREHENSIVE INCOME Three Months Ended March 31, 2016 (in millions, net of taxes) CPG CEG Columbia OpCo OpCo GP Non-guarantor Subsidiaries Consolidating adjustments and eliminations CPG Consolidated Net Income $ 86.8 $ 112.5 $ 181.4 $ — $ 179.7 $ (473.6 ) $ 86.8 Other comprehensive income Net unrealized gain on cash flow hedges 0.4 (0.1 ) — — 0.5 (0.4 ) 0.4 Unrecognized pension and OPEB benefit 0.1 0.1 — — — (0.1 ) 0.1 Total other comprehensive income 0.5 — — — 0.5 (0.5 ) 0.5 Total Comprehensive Income 87.3 112.5 181.4 — 180.2 (474.1 ) 87.3 Less: Comprehensive Income-noncontrolling interest 14.7 14.7 — — — (14.7 ) 14.7 Comprehensive Income-controlling interests $ 72.6 $ 97.8 $ 181.4 $ — $ 180.2 $ (459.4 ) $ 72.6 Three Months Ended March 31, 2015 (in millions, net of taxes) CPG CEG Columbia OpCo OpCo GP Non-guarantor Subsidiaries Consolidating adjustments and eliminations CPG Consolidated Net Income $ 97.1 $ 97.1 $ 131.9 $ — $ 130.5 $ (359.5 ) $ 97.1 Other comprehensive income Net unrealized gain on cash flow hedges 0.2 (0.1 ) — — 0.3 (0.2 ) 0.2 Unrecognized pension and OPEB benefit 7.0 7.0 — — — (7.0 ) 7.0 Total other comprehensive income 7.2 6.9 — — 0.3 (7.2 ) 7.2 Total Comprehensive Income 104.3 104.0 131.9 — 130.8 (366.7 ) 104.3 Less: Comprehensive Income-noncontrolling interest 7.1 7.1 — — — (7.1 ) 7.1 Comprehensive Income-controlling interests $ 97.2 $ 96.9 $ 131.9 $ — $ 130.8 $ (359.6 ) $ 97.2 CONDENSED CONSOLIDATING STATEMENTS OF CASH FLOWS Three Months Ended March 31, 2016 (in millions) CPG CEG Columbia OpCo OpCo GP Non-guarantor Subsidiaries Consolidating adjustments and eliminations CPG Consolidated Net Cash Flows from Operating Activities $ (6.7 ) $ 116.4 $ — $ — $ 198.2 $ (137.6 ) $ 170.3 Investing Activities Capital expenditures — — — — (388.9 ) — (388.9 ) Change in short-term lendings-affiliated (87.1 ) (109.3 ) 3.3 — 18.6 174.5 — Contributions to equity investees — — — — (1.9 ) — (1.9 ) Distributions from equity investees — — — — 0.2 — 0.2 Other investing activities — — — — (2.0 ) — (2.0 ) Net Cash Flows used for Investing Activities (87.1 ) (109.3 ) 3.3 — (374.0 ) 174.5 (392.6 ) Financing Activities Change in short-term borrowings-affiliated (99.0 ) — 124.0 — 149.5 (174.5 ) — Debt related costs (0.5 ) — — — — — (0.5 ) Quarterly distributions to unitholders — — — — (18.1 ) 18.1 — Distribution to noncontrolling interest in Columbia OpCo — — (129.2 ) — — 129.2 — Distribution to noncontrolling interest — — — — — (9.7 ) (9.7 ) Acquisition of treasury stock (6.0 ) — — — — — (6.0 ) Dividends paid - common stock (51.5 ) — — — — — (51.5 ) Net Cash Flows used for Financing Activities (157.0 ) — (5.2 ) — 131.4 (36.9 ) (67.7 ) Change in cash and cash equivalents (250.8 ) 7.1 (1.9 ) — (44.4 ) — (290.0 ) Cash and cash equivalents at beginning of period 800.0 46.7 1.9 — 82.3 — 930.9 Cash and Cash Equivalents at End of Period $ 549.2 $ 53.8 $ — $ — $ 37.9 $ — $ 640.9 CONDENSED CONSOLIDATING STATEMENTS OF CASH FLOWS (continued) Three Months Ended March 31, 2015 (in millions) CPG CEG Columbia OpCo OpCo GP Non-guarantor Subsidiaries Consolidating adjustments and eliminations CPG Consolidated Net Cash Flows from Operating Activities $ (4.6 ) $ (3.9 ) $ 0.3 $ — $ 172.0 $ — $ 163.8 Investing Activities Capital expenditures — — — — (163.9 ) — (163.9 ) Change in short-term lendings-affiliated — — (668.1 ) — (29.9 ) — (698.0 ) Proceeds from disposition of assets — — — — 10.2 — 10.2 Contributions to equity investees — (1,217.3 ) — — — 1,217.3 — Distributions from equity investees — — — — 1.3 — 1.3 Other investing activities — — — — (2.4 ) — (2.4 ) Net Cash Flows used for Investing Activities — (1,217.3 ) (668.1 ) — (184.7 ) 1,217.3 (852.8 ) Financing Activities Change in short-term borrowings-affiliated 4.6 3.9 — — (240.6 ) — (232.1 ) Issuance of long-term debt-affiliated — 1,217.3 — — — — 1,217.3 Payments of long-term debt-affiliated, including current portion — — — — (957.8 ) — (957.8 ) Proceeds from the issuance of common units, net of offering costs — — 1,170.0 — (1.6 ) — 1,168.4 Contribution of capital from parent — — — — 1,217.3 (1,217.3 ) — Distribution of IPO proceeds to parent — — (500.0 ) — — — (500.0 ) Net Cash Flows from Financing Activities 4.6 1,221.2 670.0 — 17.3 (1,217.3 ) 695.8 Change in cash and cash equivalents — — 2.2 — 4.6 — 6.8 Cash and cash equivalents at beginning of period — — — — 0.5 — 0.5 Cash and Cash Equivalents at End of Period $ — $ — $ 2.2 $ — $ 5.1 $ — $ 7.3

CPPL Initial Public Offering (T

CPPL Initial Public Offering (Tables)	3 Months Ended
	Mar. 31, 2016
Equity [Abstract]
Change From Net Income Attributable to the Partnership and Transfers to Noncontrolling Interest	Three Months Ended (in millions) 2016 2015 Net income attributable to CPG $ 72.2 $ 90.0 Increase in CPG’s net parent investment for the sale of 8.4% of Columbia OpCo — 227.1 Change from net income attributable to CPG and transfers to noncontrolling interest $ 72.2 $ 317.1

Earnings Per Share (Tables)

Earnings Per Share (Tables)	3 Months Ended
	Mar. 31, 2016
Earnings Per Share [Abstract]
Schedule of Earnings Per Share, Basic and Diluted	Three Months Ended (in millions) 2016 2015 Basic average common shares outstanding 400.3 317.6 Dilutive potential common shares: Shares restricted under stock plans 0.4 — Diluted average common shares 400.7 317.6

Transactions with Affiliates (T

Transactions with Affiliates (Tables)	3 Months Ended
	Mar. 31, 2016
Related Party Transactions [Abstract]
Schedule of Transactions with Affiliates	Statement of Operations Three Months Ended (in millions) 2016 2015 Transportation revenues $ — $ 29.0 Storage revenues — 13.3 Other revenues — 0.1 Operation and maintenance expense — 28.0 Interest expense — 18.3 Interest income — 1.0

Short-Term Borrowings (Tables)

Short-Term Borrowings (Tables)	3 Months Ended
	Mar. 31, 2016
Short-term Debt [Abstract]
Schedule of Short-Term Borrowings	(in millions) March 31, December 31, 2015 Commercial paper borrowings $ — $ — CPG credit facility borrowings — — CPPL credit facility borrowings, weighted average interest rate of 1.50% and 1.28% at March 31, 2016 and December 31, 2015, respectively 15.0 15.0 Total Short-Term Borrowings $ 15.0 $ 15.0

Asset Retirement Obligations (T

Asset Retirement Obligations (Tables)	3 Months Ended
	Mar. 31, 2016
Asset Retirement Obligation [Abstract]
Changes In Company's Liability for Asset Retirement Obligations	(in millions) 2016 2015 Balance as of January 1, $ 25.7 $ 23.2 Accretion expense 0.3 0.3 Additions — — Settlements — — Change in estimated cash flows (0.9 ) — Balance as of March 31, $ 25.1 $ 23.5

Equity Method Investments (Tabl

Equity Method Investments (Tables)	3 Months Ended
	Mar. 31, 2016
Equity Method Investments [Abstract]
Equity Method Investments	The following table contains contribution and distribution data representing CPG's portion based on CPG's ownership percentage of each investment: Three Months Ended (in millions) 2016 2015 Millennium Pipeline Contributions to Millennium Pipeline $ 1.9 $ — Distributions of earnings from Millennium Pipeline 15.2 16.6 Hardy Storage Contributions to Hardy Storage — — Distributions of earnings from Hardy Storage 0.7 0.5 Pennant Contributions to Pennant — — Distributions of earnings from Pennant 3.0 1.2 Return of capital from Pennant 0.2 1.3

Pension and Other Postretirem38

Pension and Other Postretirement Benefits (Tables)	3 Months Ended
	Mar. 31, 2016
Pension and Other Postretirement Benefit Expense [Abstract]
Components Of The Plans' Net Periodic Benefits Cost	Pension Benefits Other Postretirement Three Months Ended March 31, (in millions) 2016 2015 2016 2015 Components of Net Periodic Benefit Cost (Income) Service cost $ 1.6 $ 1.3 $ 0.2 $ 0.3 Interest cost 3.9 3.5 1.2 1.2 Expected return on assets (6.7 ) (7.0 ) (4.0 ) (4.6 ) Amortization of prior service credit (0.3 ) (0.3 ) (0.2 ) (0.2 ) Recognized actuarial loss 3.1 2.4 — — Total Net Periodic Benefit Cost (Income) $ 1.6 $ (0.1 ) $ (2.8 ) $ (3.3 )

Fair Value (Tables)

Fair Value (Tables)	3 Months Ended
	Mar. 31, 2016
Fair Value Disclosures [Abstract]
Carrying Amount And Estimated Fair Values Of Financial Instruments	(in millions) Carrying Amount as of March 31, 2016 (1) Estimated Fair Value as of March 31, 2016 Carrying Amount as of December 31, 2015 (1) Estimated Fair Value as of December 31, 2015 Long-term debt $ 2,750.0 $ 2,732.2 $ 2,750.0 $ 2,592.1 (1) The carrying amount of the Notes differs from the Long-term debt balance on the Condensed Consolidated Balance Sheets (unaudited) due to the related unamortized discount and unamortized debt issuance costs, both of which are being amortized over the weighted average life of the Notes.

Other Commitments and Conting40

Other Commitments and Contingencies (Tables)	3 Months Ended
	Mar. 31, 2016
Commitments and Contingencies Disclosure [Abstract]
Contractual Obligation, Fiscal Year Maturity Schedule	The total guarantees and indemnities in existence at March 31, 2016 and the years in which they expire were: (in millions) Total 2016 2017 2018 2019 2020 After Letters of credit $ 18.1 $ 18.1 $ — $ — $ — $ — $ — Other guarantees 45.6 0.6 2.0 — — — 43.0 Total commercial commitments $ 63.7 $ 18.7 $ 2.0 $ — $ — $ — $ 43.0

Accumulated Other Comprehensi41

Accumulated Other Comprehensive Loss (Tables)	3 Months Ended
	Mar. 31, 2016
Other Comprehensive Income (Loss), Tax [Abstract]
Components Of Accumulated Other Comprehensive Loss	Three Months Ended March 31, 2016 (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, 2016 $ (14.3 ) $ (12.7 ) $ (27.0 ) Other comprehensive income before reclassifications — 0.1 0.1 Amounts reclassified from accumulated other comprehensive income 0.4 — 0.4 Net current-period other comprehensive income 0.4 0.1 0.5 Allocation of accumulated other comprehensive loss to noncontrolling interest 0.1 — 0.1 Balance as of March 31, 2016 $ (14.0 ) $ (12.6 ) $ (26.6 ) (1) All amounts are net of tax. Amounts in parentheses indicate debits. Three Months Ended March 31, 2015 (in millions) Gains and Losses on Cash Flow Hedges (1) Pension and OPEB Items (1) Accumulated (1) Balance as of January 1, 2015 $ (16.6 ) $ (17.9 ) $ (34.5 ) Other comprehensive income before reclassifications — 6.9 6.9 Amounts reclassified from accumulated other comprehensive income 0.2 0.1 0.3 Net current-period other comprehensive income 0.2 7.0 7.2 Allocation of accumulated other comprehensive loss to noncontrolling interest 2.2 — 2.2 Balance as of March 31, 2015 $ (14.2 ) $ (10.9 ) $ (25.1 ) (1) All amounts are net of tax. Amounts in parentheses indicate debits.

Other, Net (Tables)

Other, Net (Tables)	3 Months Ended
	Mar. 31, 2016
Other Income and Expenses [Abstract]
Schedule Of Other, Net	Three Months Ended (in millions) 2016 2015 AFUDC Equity $ 6.1 $ 3.5 Miscellaneous 0.9 1.1 Total Other, net $ 7.0 $ 4.6

Supplemental Cash Flow Inform43

Supplemental Cash Flow Information (Tables)	3 Months Ended
	Mar. 31, 2016
Supplemental Cash Flow Information [Abstract]
Additional Information Regarding Condensed Statements of Consolidated and Combined Cash Flows	(in millions) 2016 2015 Supplemental Disclosures of Cash Flow Information Non-cash transactions: Capital expenditures included in current liabilities (1) $ 120.7 $ 98.8 Schedule of interest and income taxes paid: Cash paid for interest, net of interest capitalized amounts $ 6.2 $ 15.6 Cash paid for income taxes 1.1 9.4 (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 Balance Sheets (unaudited).

Concentration of Credit Risk (T

Concentration of Credit Risk (Tables)	3 Months Ended
	Mar. 31, 2016
Risks and Uncertainties [Abstract]
Schedule of Concentration Of Credit Risk	The following tables provide this customer's operating revenues and percentage of total operating revenues for the three months ended March 31, 2016 and 2015 : Three Months Ended March 31, 2016 2015 (in millions) Total Operating Revenues Percentage of Total Operating Revenues Total Operating Revenues Percentage of Total Operating Revenues Columbia Gas of Ohio (1) $ 50.4 13.8 % $ 48.9 14.4 % (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 CPG receives from Columbia Gas of Ohio in any given period.

Condensed Consolidating Finan45

Condensed Consolidating Financial Statements (Tables)	3 Months Ended
	Mar. 31, 2016
Guarantees [Abstract]
Guarantor - Condensed Consolidating Balance Sheets	CONDENSED CONSOLIDATING BALANCE SHEETS As of March 31, 2016 (in millions) CPG CEG Columbia OpCo OpCo GP Non-guarantor Subsidiaries Consolidating adjustments and eliminations CPG Consolidated ASSETS Current Assets Cash and cash equivalents $ 549.2 $ 53.8 $ — $ — $ 37.9 $ — $ 640.9 Accounts receivable, net 0.5 5.6 — — 155.4 — 161.5 Accounts receivable-affiliated 105.4 193.4 — — 135.5 (434.3 ) — Materials and supplies, at average cost — — — — 33.2 — 33.2 Exchange gas receivable — — — — 12.0 — 12.0 Deferred property taxes — — — — 54.2 — 54.2 Prepayments and other 9.3 4.6 — — 41.9 (9.3 ) 46.5 Total Current Assets 664.4 257.4 — — 470.1 (443.6 ) 948.3 Investments Unconsolidated affiliates — — — — 437.3 — 437.3 Consolidated affiliates 5,278.9 7,624.1 5,791.0 — — (18,694.0 ) — Other investments 12.0 0.3 — — 1.5 — 13.8 Total Investments 5,290.9 7,624.4 5,791.0 — 438.8 (18,694.0 ) 451.1 Property, Plant and Equipment Property, plant and equipment — — — — 9,426.0 — 9,426.0 Accumulated depreciation and amortization — — — — (3,025.1 ) — (3,025.1 ) Net Property, Plant and Equipment — — — — 6,400.9 — 6,400.9 Other Noncurrent Assets Regulatory assets — 41.1 — — 141.1 — 182.2 Goodwill — — 1,975.5 — — — 1,975.5 Notes receivable-affiliated 1,848.2 — — — — (1,848.2 ) — Postretirement and postemployment benefits assets — 0.6 — — 117.5 (0.4 ) 117.7 Deferred income taxes 23.3 — — — — (23.3 ) — Deferred charges and other 4.6 — — — 10.8 — 15.4 Total Other Noncurrent Assets 1,876.1 41.7 1,975.5 — 269.4 (1,871.9 ) 2,290.8 Total Assets $ 7,831.4 $ 7,923.5 $ 7,766.5 $ — $ 7,579.2 $ (21,009.5 ) $ 10,091.1 CONDENSED CONSOLIDATING BALANCE SHEETS (continued) As of March 31, 2016 (in millions) CPG CEG Columbia OpCo OpCo GP Non-guarantor Subsidiaries Consolidating adjustments and eliminations CPG Consolidated LIABILITIES AND EQUITY Current Liabilities Short-term borrowings $ — $ — $ — $ — $ 15.0 $ — $ 15.0 Short-term borrowings-affiliated — — 124.0 — 283.9 (407.9 ) — Accounts payable 11.0 — — — 47.7 — 58.7 Accounts payable-affiliated 7.8 14.9 0.1 — 3.6 (26.4 ) — Dividends payable 53.6 — — — — — 53.6 Customer deposits — — — — 18.8 — 18.8 Taxes accrued — 10.6 — — 99.7 (9.3 ) 101.0 Interest accrued 37.0 — — — 0.2 — 37.2 Exchange gas payable — — — — 12.1 — 12.1 Deferred revenue — — — — 10.5 — 10.5 Accrued capital expenditures — — — — 88.7 — 88.7 Accrued compensation and related costs — — — — 28.5 — 28.5 Other accruals 0.3 0.3 — — 89.3 — 89.9 Total Current Liabilities 109.7 25.8 124.1 — 698.0 (443.6 ) 514.0 Noncurrent Liabilities Long-term debt 2,725.9 — — — — — 2,725.9 Long-term debt-affiliated — 1,217.3 — — 630.9 (1,848.2 ) — Deferred income taxes — 1,396.7 — — 21.9 (23.3 ) 1,395.3 Accrued liability for postretirement and postemployment benefits 0.3 7.8 — — 41.2 (0.4 ) 48.9 Regulatory liabilities — 10.4 — — 293.2 — 303.6 Asset retirement obligations — — — — 25.1 — 25.1 Other noncurrent liabilities 11.6 0.3 — — 82.5 — 94.4 Total Noncurrent Liabilities 2,737.8 2,632.5 — — 1,094.8 (1,871.9 ) 4,593.2 Total Liabilities 2,847.5 2,658.3 124.1 — 1,792.8 (2,315.5 ) 5,107.2 Equity Common stock 4.0 — — — — — 4.0 Additional paid-in capital 4,037.1 — — — — — 4,037.1 Retained earnings 14.0 — — — — — 14.0 Net parent investment — 4,330.2 7,667.3 — 5,815.4 (17,812.9 ) — Treasury stock (6.0 ) — — — — — (6.0 ) Accumulated other comprehensive loss (26.6 ) (26.4 ) (24.9 ) — (29.0 ) 80.3 (26.6 ) Total CPG Equity 4,022.5 4,303.8 7,642.4 — 5,786.4 (17,732.6 ) 4,022.5 Noncontrolling Interest 961.4 961.4 — — — (961.4 ) 961.4 Total Equity 4,983.9 5,265.2 7,642.4 — 5,786.4 (18,694.0 ) 4,983.9 Total Liabilities and Equity $ 7,831.4 $ 7,923.5 $ 7,766.5 $ — $ 7,579.2 $ (21,009.5 ) $ 10,091.1 CONDENSED CONSOLIDATING BALANCE SHEETS (continued) As of December 31, 2015 (in millions) CPG CEG Columbia OpCo OpCo GP Non-guarantor Subsidiaries Consolidating adjustments and eliminations CPG Consolidated ASSETS Current Assets Cash and cash equivalents $ 800.0 $ 46.7 $ 1.9 $ — $ 82.3 $ — $ 930.9 Accounts receivable, net — 5.6 — — 146.8 — 152.4 Accounts receivable-affiliated 14.6 85.6 3.4 — 156.4 (260.0 ) — Materials and supplies, at average cost — — — — 32.8 — 32.8 Exchange gas receivable — — — — 19.0 — 19.0 Deferred property taxes — — — — 52.0 — 52.0 Prepayments and other 0.3 10.1 — — 43.8 (5.7 ) 48.5 Total Current Assets 814.9 148.0 5.3 — 533.1 (265.7 ) 1,235.6 Investments Unconsolidated affiliates — — — — 438.1 — 438.1 Consolidated affiliates 5,174.6 7,569.8 5,608.9 — — (18,353.3 ) — Other investments 12.0 0.3 — — 1.5 — 13.8 Total Investments 5,186.6 7,570.1 5,608.9 — 439.6 (18,353.3 ) 451.9 Property, Plant and Equipment Property, plant and equipment — — — — 9,052.3 — 9,052.3 Accumulated depreciation and amortization — — — — (2,988.6 ) — (2,988.6 ) Net Property, Plant and Equipment — — — — 6,063.7 — 6,063.7 Other Noncurrent Assets Regulatory assets — 35.1 — — 142.6 — 177.7 Goodwill — — 1,975.5 — — — 1,975.5 Notes receivable-affiliated 1,848.2 — — — — (1,848.2 ) — Postretirement and postemployment benefits assets — 0.5 — — 115.6 (0.4 ) 115.7 Deferred income taxes 18.9 — — — — (18.9 ) — Deferred charges and other 4.9 — — — 10.6 — 15.5 Total Other Noncurrent Assets 1,872.0 35.6 1,975.5 — 268.8 (1,867.5 ) 2,284.4 Total Assets $ 7,873.5 $ 7,753.7 $ 7,589.7 $ — $ 7,305.2 $ (20,486.5 ) $ 10,035.6 CONDENSED CONSOLIDATING BALANCE SHEETS (continued) As of December 31, 2015 (in millions) CPG CEG Columbia OpCo OpCo GP Non-guarantor Subsidiaries Consolidating adjustments and eliminations CPG Consolidated LIABILITIES AND EQUITY Current Liabilities Short-term borrowings $ — $ — $ — $ — $ 15.0 $ — $ 15.0 Short-term borrowings-affiliated 99.0 — — — 134.3 (233.3 ) — Accounts payable 0.1 — — — 56.7 — 56.8 Accounts payable-affiliated 10.8 4.8 — — 11.1 (26.7 ) — Customer deposits — — — — 17.9 — 17.9 Taxes accrued — — — — 111.7 (5.7 ) 106.0 Interest accrued 9.4 — — — 0.1 — 9.5 Exchange gas payable — — — — 18.6 — 18.6 Deferred revenue — — — — 15.0 — 15.0 Accrued capital expenditures — — — — 100.1 — 100.1 Accrued compensation and related costs — — — — 51.9 — 51.9 Other accruals — 0.3 — — 69.7 — 70.0 Total Current Liabilities 119.3 5.1 — — 602.1 (265.7 ) 460.8 Noncurrent Liabilities Long-term debt 2,725.6 — — — — — 2,725.6 Long-term debt-affiliated — 1,217.3 — — 630.9 (1,848.2 ) — Deferred income taxes — 1,350.4 — — 16.6 (18.9 ) 1,348.1 Accrued liability for postretirement and postemployment benefits 0.3 8.3 — — 41.2 (0.4 ) 49.4 Regulatory liabilities — 10.5 — — 311.1 — 321.6 Asset retirement obligations — — — — 25.7 — 25.7 Other noncurrent liabilities 15.3 0.2 — — 75.9 — 91.4 Total Noncurrent Liabilities 2,741.2 2,586.7 — — 1,101.4 (1,867.5 ) 4,561.8 Total Liabilities 2,860.5 2,591.8 — — 1,703.5 (2,133.2 ) 5,022.6 Equity Common stock 4.0 — — — — — 4.0 Additional paid-in capital 4,032.7 — — — — — 4,032.7 Retained earnings 46.9 — — — — — 46.9 Net parent investment — 4,232.3 7,615.4 — 5,631.3 (17,479.0 ) — Accumulated other comprehensive loss (27.0 ) (26.8 ) (25.7 ) — (29.6 ) 82.1 (27.0 ) Total CPG Equity 4,056.6 4,205.5 7,589.7 — 5,601.7 (17,396.9 ) 4,056.6 Noncontrolling Interest 956.4 956.4 — — — (956.4 ) 956.4 Total Equity 5,013.0 5,161.9 7,589.7 — 5,601.7 (18,353.3 ) 5,013.0 Total Liabilities and Equity $ 7,873.5 $ 7,753.7 $ 7,589.7 $ — $ 7,305.2 $ (20,486.5 ) $ 10,035.6
Guarantor - Condensed Consolidating Statements of Operations	CONDENSED CONSOLIDATING STATEMENTS OF OPERATIONS Three Months Ended March 31, 2016 (in millions) CPG CEG Columbia OpCo OpCo GP Non-guarantor Subsidiaries Consolidating adjustments and eliminations CPG Consolidated Operating Revenues Transportation revenues $ — $ — $ — $ — $ 308.5 $ — $ 308.5 Transportation revenues-affiliated — — — — — — — Storage revenues — — — — 49.9 — 49.9 Storage revenues-affiliated — — — — — — — Other revenues — — — — 6.1 — 6.1 Total Operating Revenues — — — — 364.5 — 364.5 Operating Expenses Operation and maintenance 30.4 (0.2 ) — — 139.1 (0.2 ) 169.1 Operation and maintenance-affiliated 0.1 — — — — (0.1 ) — Depreciation and amortization — 0.2 — — 40.2 — 40.4 Gain on sale of assets — — — — (2.6 ) — (2.6 ) Property and other taxes 0.1 — — — 21.7 — 21.8 Total Operating Expenses 30.6 — — — 198.4 (0.3 ) 228.7 Equity Earnings in Unconsolidated Affiliates — — — — 15.9 — 15.9 Equity Earnings in Consolidated Affiliates 113.5 179.8 181.5 — — (474.8 ) — Operating Income 82.9 179.8 181.5 — 182.0 (474.5 ) 151.7 Other Income (Deductions) Interest expense (29.5 ) — — — (0.6 ) 0.7 (29.4 ) Interest expense-affiliated — (11.2 ) (0.1 ) — (7.2 ) 18.5 — Other, net 19.7 0.5 — — 6.0 (19.2 ) 7.0 Total Other Deductions, net (9.8 ) (10.7 ) (0.1 ) — (1.8 ) — (22.4 ) Income from Continuing Operations before Income Taxes 73.1 169.1 181.4 — 180.2 (474.5 ) 129.3 Income Taxes (13.5 ) 56.8 — — 0.5 (1.1 ) 42.7 Income from Continuing Operations 86.6 112.3 181.4 — 179.7 (473.4 ) 86.6 Income from Discontinued Operations-net of taxes 0.2 0.2 — — — (0.2 ) 0.2 Net Income 86.8 112.5 181.4 — 179.7 (473.6 ) 86.8 Less: Net income attributable to noncontrolling interest 14.6 14.6 — — — (14.6 ) 14.6 Net Income Attributable to CPG $ 72.2 $ 97.9 $ 181.4 $ — $ 179.7 $ (459.0 ) $ 72.2 CONDENSED CONSOLIDATING STATEMENTS OF OPERATIONS (continued) Three Months Ended March 31, 2015 (in millions) CPG CEG Columbia OpCo OpCo GP Non-guarantor Subsidiaries Consolidating adjustments and eliminations CPG Consolidated Operating Revenues Transportation revenues $ — $ — $ — $ — $ 248.4 $ — $ 248.4 Transportation revenues-affiliated — — — — 29.0 — 29.0 Storage revenues — — — — 36.6 — 36.6 Storage revenues-affiliated — — — — 13.3 — 13.3 Other revenues — — — — 12.7 — 12.7 Total Operating Revenues — — — — 340.0 — 340.0 Operating Expenses Operation and maintenance — (0.1 ) — — 118.5 — 118.4 Operation and maintenance-affiliated — 0.1 — — 27.9 — 28.0 Depreciation and amortization — — — — 32.5 — 32.5 Gain on sale of assets — — — — (5.3 ) — (5.3 ) Property and other taxes — — — — 19.1 — 19.1 Total Operating Expenses — — — — 192.7 — 192.7 Equity Earnings in Unconsolidated Affiliates — — — — 15.4 — 15.4 Equity Earnings in Consolidated Affiliates 97.1 131.2 131.2 — — (359.5 ) — Operating Income 97.1 131.2 131.2 — 162.7 (359.5 ) 162.7 Other Income (Deductions) Interest expense-affiliated — (6.9 ) — — (11.4 ) — (18.3 ) Other, net — 0.4 0.7 — 3.5 — 4.6 Total Other Deductions, net — (6.5 ) 0.7 — (7.9 ) — (13.7 ) Income before Income Taxes 97.1 124.7 131.9 — 154.8 (359.5 ) 149.0 Income Taxes — 27.6 — — 24.3 — 51.9 Net Income 97.1 97.1 131.9 — 130.5 (359.5 ) 97.1 Less: Net income attributable to noncontrolling interest 7.1 7.1 — — — (7.1 ) 7.1 Net Income Attributable to CPG $ 90.0 $ 90.0 $ 131.9 $ — $ 130.5 $ (352.4 ) $ 90.0
Guarantor - Condensed Consolidating Statements of Comprehensive Income	CONDENSED CONSOLIDATING STATEMENTS OF COMPREHENSIVE INCOME Three Months Ended March 31, 2016 (in millions, net of taxes) CPG CEG Columbia OpCo OpCo GP Non-guarantor Subsidiaries Consolidating adjustments and eliminations CPG Consolidated Net Income $ 86.8 $ 112.5 $ 181.4 $ — $ 179.7 $ (473.6 ) $ 86.8 Other comprehensive income Net unrealized gain on cash flow hedges 0.4 (0.1 ) — — 0.5 (0.4 ) 0.4 Unrecognized pension and OPEB benefit 0.1 0.1 — — — (0.1 ) 0.1 Total other comprehensive income 0.5 — — — 0.5 (0.5 ) 0.5 Total Comprehensive Income 87.3 112.5 181.4 — 180.2 (474.1 ) 87.3 Less: Comprehensive Income-noncontrolling interest 14.7 14.7 — — — (14.7 ) 14.7 Comprehensive Income-controlling interests $ 72.6 $ 97.8 $ 181.4 $ — $ 180.2 $ (459.4 ) $ 72.6 Three Months Ended March 31, 2015 (in millions, net of taxes) CPG CEG Columbia OpCo OpCo GP Non-guarantor Subsidiaries Consolidating adjustments and eliminations CPG Consolidated Net Income $ 97.1 $ 97.1 $ 131.9 $ — $ 130.5 $ (359.5 ) $ 97.1 Other comprehensive income Net unrealized gain on cash flow hedges 0.2 (0.1 ) — — 0.3 (0.2 ) 0.2 Unrecognized pension and OPEB benefit 7.0 7.0 — — — (7.0 ) 7.0 Total other comprehensive income 7.2 6.9 — — 0.3 (7.2 ) 7.2 Total Comprehensive Income 104.3 104.0 131.9 — 130.8 (366.7 ) 104.3 Less: Comprehensive Income-noncontrolling interest 7.1 7.1 — — — (7.1 ) 7.1 Comprehensive Income-controlling interests $ 97.2 $ 96.9 $ 131.9 $ — $ 130.8 $ (359.6 ) $ 97.2
Guarantor - Condensed Consolidating Statements of Cash Flows	CONDENSED CONSOLIDATING STATEMENTS OF CASH FLOWS Three Months Ended March 31, 2016 (in millions) CPG CEG Columbia OpCo OpCo GP Non-guarantor Subsidiaries Consolidating adjustments and eliminations CPG Consolidated Net Cash Flows from Operating Activities $ (6.7 ) $ 116.4 $ — $ — $ 198.2 $ (137.6 ) $ 170.3 Investing Activities Capital expenditures — — — — (388.9 ) — (388.9 ) Change in short-term lendings-affiliated (87.1 ) (109.3 ) 3.3 — 18.6 174.5 — Contributions to equity investees — — — — (1.9 ) — (1.9 ) Distributions from equity investees — — — — 0.2 — 0.2 Other investing activities — — — — (2.0 ) — (2.0 ) Net Cash Flows used for Investing Activities (87.1 ) (109.3 ) 3.3 — (374.0 ) 174.5 (392.6 ) Financing Activities Change in short-term borrowings-affiliated (99.0 ) — 124.0 — 149.5 (174.5 ) — Debt related costs (0.5 ) — — — — — (0.5 ) Quarterly distributions to unitholders — — — — (18.1 ) 18.1 — Distribution to noncontrolling interest in Columbia OpCo — — (129.2 ) — — 129.2 — Distribution to noncontrolling interest — — — — — (9.7 ) (9.7 ) Acquisition of treasury stock (6.0 ) — — — — — (6.0 ) Dividends paid - common stock (51.5 ) — — — — — (51.5 ) Net Cash Flows used for Financing Activities (157.0 ) — (5.2 ) — 131.4 (36.9 ) (67.7 ) Change in cash and cash equivalents (250.8 ) 7.1 (1.9 ) — (44.4 ) — (290.0 ) Cash and cash equivalents at beginning of period 800.0 46.7 1.9 — 82.3 — 930.9 Cash and Cash Equivalents at End of Period $ 549.2 $ 53.8 $ — $ — $ 37.9 $ — $ 640.9 CONDENSED CONSOLIDATING STATEMENTS OF CASH FLOWS (continued) Three Months Ended March 31, 2015 (in millions) CPG CEG Columbia OpCo OpCo GP Non-guarantor Subsidiaries Consolidating adjustments and eliminations CPG Consolidated Net Cash Flows from Operating Activities $ (4.6 ) $ (3.9 ) $ 0.3 $ — $ 172.0 $ — $ 163.8 Investing Activities Capital expenditures — — — — (163.9 ) — (163.9 ) Change in short-term lendings-affiliated — — (668.1 ) — (29.9 ) — (698.0 ) Proceeds from disposition of assets — — — — 10.2 — 10.2 Contributions to equity investees — (1,217.3 ) — — — 1,217.3 — Distributions from equity investees — — — — 1.3 — 1.3 Other investing activities — — — — (2.4 ) — (2.4 ) Net Cash Flows used for Investing Activities — (1,217.3 ) (668.1 ) — (184.7 ) 1,217.3 (852.8 ) Financing Activities Change in short-term borrowings-affiliated 4.6 3.9 — — (240.6 ) — (232.1 ) Issuance of long-term debt-affiliated — 1,217.3 — — — — 1,217.3 Payments of long-term debt-affiliated, including current portion — — — — (957.8 ) — (957.8 ) Proceeds from the issuance of common units, net of offering costs — — 1,170.0 — (1.6 ) — 1,168.4 Contribution of capital from parent — — — — 1,217.3 (1,217.3 ) — Distribution of IPO proceeds to parent — — (500.0 ) — — — (500.0 ) Net Cash Flows from Financing Activities 4.6 1,221.2 670.0 — 17.3 (1,217.3 ) 695.8 Change in cash and cash equivalents — — 2.2 — 4.6 — 6.8 Cash and cash equivalents at beginning of period — — — — 0.5 — 0.5 Cash and Cash Equivalents at End of Period $ — $ — $ 2.2 $ — $ 5.1 $ — $ 7.3

Basis of Accounting Presentat46

Basis of Accounting Presentation (Narrative) (Details) shares in Millions, $ in Millions	3 Months Ended	6 Months Ended
	Mar. 31, 2016mi	Jun. 30, 2015USD ($)	Jul. 01, 2015shares	May. 22, 2015USD ($)
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Pipeline Miles | mi	15,000
Common Stock, Shares, Issued | shares			317.6
Senior notes proceeds				$ 2,722.3
Repayments of Related Party Debt		$ 1,087.3
Distribution to NiSource		$ 1,450
Limited Liability Company (LLC) or Limited Partnership (LP), Members or Limited Partners, Ownership Interest	46.50%

CPPL Initial Public Offering (N

CPPL Initial Public Offering (Narrative) (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Initial Public Offering [Line Items]
Issuance of common units of CPPL		$ 1,168.4
Limited Liability Company (LLC) or Limited Partnership (LP), Members or Limited Partners, Ownership Interest	46.50%
Columbia Pipeline Partners LP
Initial Public Offering [Line Items]
Limited Liability Company (LLC) or Limited Partnership (LP), Members or Limited Partners, Ownership Interest		53.50%
Columbia OpCo
Initial Public Offering [Line Items]
Limited Liability Company (LLC) or Limited Partnership (LP), Members or Limited Partners, Ownership Interest		15.70%
Noncontrolling Interest
Initial Public Offering [Line Items]
Issuance of common units of CPPL		$ 1,168.4
Common Units | Noncontrolling Interest
Initial Public Offering [Line Items]
Partners' Capital Account, Units, Sold in Public Offering		53.8

CPPL Initial Public Offering (S

CPPL Initial Public Offering (Schedule of Change From Net Income Attributable to the Partnership and Transfers to Noncontrolling Interest) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Initial Public Offering [Line Items]
Net income attributable to CPG	$ 72.2	$ 90
Increase for sale of limited partner interest	0	227.1
Change from net income attributable to parent and transfers to noncontrolling interest	$ 72.2	$ 317.1

Recent Accounting Pronounceme49

Recent Accounting Pronouncements (Narrative) (Details) $ in Millions	Dec. 31, 2015USD ($)
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
Unamortized debt issuance costs	$ 20.6
New Accounting Pronouncement, Cumulative Effect of Change on Net Assets	$ 20.6

Earnings Per Share (Narrative)

Earnings Per Share (Narrative) (Details) - $ / shares shares in Millions	Mar. 22, 2016	Feb. 19, 2016	Mar. 31, 2016	Mar. 31, 2015	Jul. 01, 2015
Earnings Per Share [Abstract]
Common Stock, Shares, Issued					317.6
Common Stock, Dividends, Per Share, Cash Paid		$ 0.12875
Dividends Declared Per Common Share	$ 0.13375		$ 0.26	$ 0
Dividends Payable, Date of Record	Apr. 29, 2016
Dividends Payable, Date to be Paid	May 20, 2016

Earnings Per Share (Schedule of

Earnings Per Share (Schedule of Diluted Average Common Shares) (Details) - shares shares in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Earnings Per Share [Abstract]
Basic average common shares outstanding	400.3	317.6
Shares restricted under stock plans	0.4	0
Diluted average common shares	400.7	317.6

Transactions with Affiliates (N

Transactions with Affiliates (Narrative) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2015USD ($)
Related Party Transaction [Line Items]
Interest Expense, Long-term Debt	$ 19
Allowance for Funds Used During Construction, Capitalized Interest	1
Interest Expense, Short-term Borrowings	$ 0.3
Money Pool
Related Party Transaction [Line Items]
Short-Term Borrowings, Weighted Average Interest Rate	1.07%
Columbia OpCo
Related Party Transaction [Line Items]
Reimbursement of preformation capital	$ 500

Transactions with Affiliates (S

Transactions with Affiliates (Schedule of Affiliated Transactions) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Related Party Transaction [Line Items]
Transportation revenues	$ 0	$ 29
Storage revenues	0	13.3
Other revenues	0	0.1
Operation and maintenance	0	28
Interest expense	0	18.3
Interest income	$ 0	$ 1

Short-Term Borrowings (Narrativ

Short-Term Borrowings (Narrative) (Details) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2016USD ($)$ / shares	Dec. 31, 2015USD ($)	Dec. 05, 2014USD ($)
Short-term Debt [Line Items]
Line of Credit Facility Used For Credit Support for Subsidiaries	$ 750
Line of Credit Facility Used For Corporate Purposes	750
Default Provision Floor	50
Letter of Credit
Short-term Debt [Line Items]
Revolving credit facility, Maximum Borrowing Capacity	250
Letters of Credit Outstanding, Amount	18.1	$ 18.1
Revolving Credit Facility
Short-term Debt [Line Items]
Revolving credit facility, Maximum Borrowing Capacity	1,500
Line of Credit	0	0
Commercial Paper
Short-term Debt [Line Items]
Revolving credit facility, Maximum Borrowing Capacity	1,000
Commercial Paper	0	0
CPPL
Short-term Debt [Line Items]
Default Provision Floor	50
CPPL | Letter of Credit
Short-term Debt [Line Items]
Revolving credit facility, Maximum Borrowing Capacity	50
Letters of Credit Outstanding, Amount	0	0
CPPL | Revolving Credit Facility
Short-term Debt [Line Items]
Revolving credit facility, Maximum Borrowing Capacity			$ 500
Line of Credit	$ 15	$ 15
Minimum
Short-term Debt [Line Items]
Line of Credit Facility, Commitment Fee Percentage	0.125%
Minimum | CPPL
Short-term Debt [Line Items]
Distribution Policy, Minimum | $ / shares	$ 0.1675
Maximum
Short-term Debt [Line Items]
Line of Credit Facility, Commitment Fee Percentage	0.35%
Period 1 | Minimum
Short-term Debt [Line Items]
Ratio of Indebtedness to Net Capital	5.50
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
Period 2 | Maximum
Short-term Debt [Line Items]
Ratio of Indebtedness to Net Capital	1
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
Short-term Debt [Line Items]
Margin Rate	1.00%
Eurodollar | Minimum
Short-term Debt [Line Items]
Margin Rate	1.00%
Eurodollar | Maximum
Short-term Debt [Line Items]
Margin Rate	1.65%

Short-Term Borrowings (Schedule

Short-Term Borrowings (Schedule of Short-Term Borrowings) (Details) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Short-term Debt [Line Items]
Short-term borrowings	$ 15	$ 15
Commercial Paper
Short-term Debt [Line Items]
Commercial Paper	0	0
Revolving Credit Facility
Short-term Debt [Line Items]
Credit facilities borrowings	0	0
CPPL | Revolving Credit Facility
Short-term Debt [Line Items]
Credit facilities borrowings	$ 15	$ 15
Short-Term Borrowings, Weighted Average Interest Rate	1.50%	1.28%

Long-Term Debt (Narrative) (Det

Long-Term Debt (Narrative) (Details) - USD ($) $ in Millions	May. 22, 2015	Mar. 31, 2016
Debt Instrument [Line Items]
Senior notes proceeds	$ 2,722.3
Senior Notes
Debt Instrument [Line Items]
Face amount of notes		$ 2,750
Debt Instrument, Issuance Date	May 22, 2015
Senior Notes | Notes Due 2018
Debt Instrument [Line Items]
Face amount of notes	$ 500
Debt Instrument, Interest Rate, Stated Percentage	2.45%
Debt Instrument, Maturity Date	Jun. 1, 2018
Senior Notes | Notes Due 2020
Debt Instrument [Line Items]
Face amount of notes	$ 750
Debt Instrument, Interest Rate, Stated Percentage	3.30%
Debt Instrument, Maturity Date	Jun. 1, 2020
Senior Notes | Notes Due 2025
Debt Instrument [Line Items]
Face amount of notes	$ 1,000
Debt Instrument, Interest Rate, Stated Percentage	4.50%
Debt Instrument, Maturity Date	Jun. 1, 2025
Senior Notes | Notes Due 2045
Debt Instrument [Line Items]
Face amount of notes	$ 500
Debt Instrument, Interest Rate, Stated Percentage	5.80%
Debt Instrument, Maturity Date	Jun. 1, 2045

Gain on Sale of Assets (Narrati

Gain on Sale of Assets (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Gain On Sale of Assets [Abstract]
Gain on Conveyances	$ 2.6	$ 5.3
Deferred Gains On Conveyances	$ 5.5		$ 8.1

Goodwill (Narrative) (Details)

Goodwill (Narrative) (Details) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Goodwill [Abstract]
Goodwill	$ 1,975.5	$ 1,975.5

Asset Retirement Obligations (C

Asset Retirement Obligations (Changes In Company's Liability For Asset Retirement Obligations) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Asset Retirement Obligation [Abstract]
Beginning Balance	$ 25.7	$ 23.2
Accretion expense	0.3	0.3
Additions	0	0
Settlements	0	0
Change in estimated cash flows	(0.9)	0
Ending Balance	$ 25.1	$ 23.5

Regulatory Matters (Narrative)

Regulatory Matters (Narrative) (Details) - USD ($) $ in Millions	Jan. 01, 2015	Mar. 31, 2016	Feb. 01, 2015
Regulatory Assets and Liabilities Disclosure [Abstract]
Expected Modernization Investment	$ 300
Modernization Program Recovery			$ 320
Annual Capital Cost Recovery Mechanism Extension Limit		$ 1,100

Equity Method Investments (Sche

Equity Method Investments (Schedule of Equity Method Investments) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Millennium Pipeline
Schedule of Equity Method Investments [Line Items]
Contributions to equity investees	$ 1.9	$ 0
Distributions of earnings from equity investees	15.2	16.6
Hardy Storage
Schedule of Equity Method Investments [Line Items]
Contributions to equity investees	0	0
Distributions of earnings from equity investees	0.7	0.5
Pennant
Schedule of Equity Method Investments [Line Items]
Contributions to equity investees	0	0
Distributions of earnings from equity investees	3	1.2
Return of capital from equity investees	$ 0.2	$ 1.3

Income Taxes (Narrative) (Detai

Income Taxes (Narrative) (Details)	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Income Taxes [Line Items]
Effective income tax rates	33.00%	34.80%
Federal statutory income tax rate	35.00%	35.00%

Pension and Other Postretirem63

Pension and Other Postretirement Benefits (Components Of The Plans' Net Periodic Benefits Cost) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 1.6	$ 1.3
Interest cost	3.9	3.5
Expected return on assets	(6.7)	(7)
Amortization of prior service credit	(0.3)	(0.3)
Recognized actuarial loss	3.1	2.4
Total Net Periodic Benefit Cost (Income)	1.6	(0.1)
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	0.2	0.3
Interest cost	1.2	1.2
Expected return on assets	(4)	(4.6)
Amortization of prior service credit	(0.2)	(0.2)
Recognized actuarial loss	0	0
Total Net Periodic Benefit Cost (Income)	$ (2.8)	$ (3.3)

Fair Value (Carrying Amount And

Fair Value (Carrying Amount And Estimated Fair Values Of Financial Instruments) (Details) - USD ($) $ in Millions		Mar. 31, 2016	Dec. 31, 2015
Fair Value Disclosures [Abstract]
Long-term debt, carrying amount	[1]	$ 2,750	$ 2,750
Long-term debt, estimated fair value		$ 2,732.2	$ 2,592.1
[1]	The carrying amount of the Notes differs from the Long-term debt balance on the Condensed Consolidated Balance Sheets (unaudited) due to the related unamortized discount and unamortized debt issuance costs, both of which are being amortized over the weighted average life of the Notes.

Share-Based Compensation (Narra

Share-Based Compensation (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock available for awards, shares	8,000,000
Common stock reserved for future awards, shares	4,227,203
Stock-based compensation expense	$ 3.8	$ 1.8
Tax benefit from stock-based compensation expense	1.4	0.6
Unrecognized compensation cost related to nonvested awards	$ 33.2
Weighted-average remaining requisite service period, years	2 years 5 months
Defined Contribution Plan, Cost Recognized	$ 3.2	$ 1.7
CPG Plan | Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted	12,144
Grant date fair-value	$ 0.2
Nonvested	1,373,018
CPG Plan | Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted	995,848
Grant date fair-value	$ 17
Nonvested	1,117,352
Omnibus Plan | Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares Issued	52,427
Omnibus Plan | NiSource Plan | Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares Issued	13,495
Share Based Goods And Nonemployee Services Transaction Quantity Of Securities Converted	21,399
Omnibus Plan | CPG Plan | Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares Issued	31,028
Director Plan [Member] | Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares Issued	228,619

Other Commitments and Conting66

Other Commitments and Contingencies (Narrative) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 05, 2014USD ($)
Other Commitments [Line Items]
Line of Credit Facility Used For Credit Support for Subsidiaries	$ 750
Line of Credit Facility Used For Corporate Purposes	750
Guarantor Obligations, Maximum Exposure	63.7
Accrual for Environmental Loss Contingencies	$ 8.2	$ 8.3
Ozone Level Maximum	70 ppb
Percentage Reduction in Methane Emissions	95.00%
Hours of Operation	26,000
Replacement Years	3 years
Millennium Pipeline
Other Commitments [Line Items]
Guarantor Obligations, Maximum Exposure	$ 16.2
Guarantees, Fair Value	1.5
Senior Notes
Other Commitments [Line Items]
Face amount of notes	2,750
Letter of Credit
Other Commitments [Line Items]
Revolving credit facility, Maximum Borrowing Capacity	250
Letters of Credit Outstanding, Amount	18.1	18.1
Letter of Credit | CPPL
Other Commitments [Line Items]
Revolving credit facility, Maximum Borrowing Capacity	50
Letters of Credit Outstanding, Amount	0	0
Revolving Credit Facility
Other Commitments [Line Items]
Revolving credit facility, Maximum Borrowing Capacity	1,500
Line of Credit	0	0
Revolving Credit Facility | CPPL
Other Commitments [Line Items]
Revolving credit facility, Maximum Borrowing Capacity			$ 500
Line of Credit	15	15
Commercial Paper
Other Commitments [Line Items]
Revolving credit facility, Maximum Borrowing Capacity	1,000
Commercial Paper	0	0
Letter of Credit
Other Commitments [Line Items]
Guarantor Obligations, Maximum Exposure	18.1
Guarantee Type, Other
Other Commitments [Line Items]
Guarantor Obligations, Maximum Exposure	45.6
PCB
Other Commitments [Line Items]
Liability for Estimated Remediation Costs	1.8	1.8
Former Propane and Petroleum Operations
Other Commitments [Line Items]
Liability for Estimated Remediation Costs	$ 6.4	$ 6.5
Millennium Pipeline
Other Commitments [Line Items]
Percentage of Ownership Interest	47.50%

Other Commitments and Conting67

Other Commitments and Contingencies (Existence and Expiration of Commercial Commitments) (Details) $ in Millions	Mar. 31, 2016USD ($)
Other Commitments and Contingencies [Line Items]
2,016	$ 18.7
2,017	2
2,018	0
2,019	0
2,020	0
Thereafter	43
Total	63.7
Letter of Credit
Other Commitments and Contingencies [Line Items]
2,016	18.1
2,017	0
2,018	0
2,019	0
2,020	0
Thereafter	0
Total	18.1
Guarantee Type, Other
Other Commitments and Contingencies [Line Items]
2,016	0.6
2,017	2
2,018	0
2,019	0
2,020	0
Thereafter	43
Total	$ 45.6

Accumulated Other Comprehensi68

Accumulated Other Comprehensive Loss (Narrative) (Details) - Millennium Pipeline - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Accumulated Other Comprehensive Loss [Line Items]
Other Comprehensive Income Unrecognized Gain Loss On Derivatives Arising During Period Net Of Tax	$ 14	$ 14.3
Unrealized loss, amortization period	15 years
Debt Instrument, Maturity Date	Jun. 1, 2025

Accumulated Other Comprehensi69

Accumulated Other Comprehensive Loss (Components Of Accumulated Other Comprehensive Loss) (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2016	Mar. 31, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	[1]	$ (27)	$ (34.5)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	[1]	0.1	6.9
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	[1]	0.4	0.3
Other Comprehensive Income (Loss), Net of Tax	[1]	0.5	7.2
Ending Balance	[1]	(26.6)	(25.1)
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	[1]	(14.3)	(16.6)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	[1]	0	0
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	[1]	0.4	0.2
Other Comprehensive Income (Loss), Net of Tax	[1]	0.4	0.2
Ending Balance	[1]	(14)	(14.2)
Accumulated Defined Benefit Plans Adjustment
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	[1]	(12.7)	(17.9)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	[1]	0.1	6.9
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	[1]	0	0.1
Other Comprehensive Income (Loss), Net of Tax	[1]	0.1	7
Ending Balance	[1]	(12.6)	(10.9)
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Noncontrolling Interest
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), Net of Tax	[1]	0.1	2.2
Accumulated Defined Benefit Plans Adjustment Attributable to Noncontrolling Interest
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), Net of Tax	[1]	0	0
AOCI Attributable to Noncontrolling Interest
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), Net of Tax	[1]	$ 0.1	$ 2.2
[1]	All amounts are net of tax. Amounts in parentheses indicate debits.

Other, Net (Schedule of Other,

Other, Net (Schedule of Other, Net) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Other Income and Expenses [Abstract]
AFUDC Equity	$ 6.1	$ 3.5
Miscellaneous	0.9	1.1
Total Other, net	$ 7	$ 4.6

Supplemental Cash Flow Inform71

Supplemental Cash Flow Information (Schedule of Supplemental Cash Flow Information) (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2016	Mar. 31, 2015
Supplemental Cash Flow [Line Items]
Capital expenditures included in current liabilities	[1]	$ 120.7	$ 98.8
Cash paid for interest, net of interest capitalized amounts		6.2	15.6
Cash paid for income taxes		$ 1.1	$ 9.4
[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 Balance Sheets (unaudited).

Concentration of Credit Risk (N

Concentration of Credit Risk (Narrative) (Details)	3 Months Ended
	Mar. 31, 2016
Risks and Uncertainties [Abstract]
Concentration Risk, Benchmark Description	10% of total operating revenues

Concentration of Credit Risk (S

Concentration of Credit Risk (Schedule of Concentration Of Credit Risk) (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2016	Mar. 31, 2015
Concentration Risk [Line Items]
Revenues		$ 364.5	$ 340
Credit Concentration Risk
Concentration Risk [Line Items]
Revenues	[1]	$ 50.4	$ 48.9
Concentration Risk, Percentage	[1]	13.80%	14.40%
[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 CPG receives from Columbia Gas of Ohio in any given period.

Condensed Consolidating Finan74

Condensed Consolidating Financial Statements (Narrative) (Details) $ in Millions	Mar. 31, 2016USD ($)
Senior Notes
Guarantor Obligations [Line Items]
Face amount of notes	$ 2,750

Condensed Consolidating Finan75

Condensed Consolidating Financial Statements (Condensed Consolidating Balance Sheets) (Details) - USD ($) $ in Millions		Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015	Dec. 31, 2014
Current Assets
Cash and cash equivalents		$ 640.9	$ 930.9	$ 7.3	$ 0.5
Accounts receivable, net		161.5	152.4
Accounts receivable-affiliated		0	0
Materials and supplies, at average cost		33.2	32.8
Exchange gas receivable		12	19
Deferred property taxes		54.2	52
Prepayments and other		46.5	48.5
Total Current Assets		948.3	1,235.6
Investments
Unconsolidated affiliates		437.3	438.1
Consolidated affiliates		0	0
Other investments		13.8	13.8
Total Investments		451.1	451.9
Property, Plant and Equipment
Property, plant and equipment		9,426	9,052.3
Accumulated depreciation and amortization		(3,025.1)	(2,988.6)
Net Property, Plant and Equipment		6,400.9	6,063.7
Other Noncurrent Assets
Regulatory assets		182.2	177.7
Goodwill		1,975.5	1,975.5
Notes receivable-affiliated		0	0
Postretirement and postemployment benefits assets		117.7	115.7
Deferred income taxes		0	0
Deferred charges and other		15.4	15.5
Total Other Noncurrent Assets		2,290.8	2,284.4
Total Assets		10,091.1	10,035.6
Current Liabilities
Short-term borrowings		15	15
Short-term borrowings-affiliated		0	0
Accounts payable		58.7	56.8
Accounts payable-affiliated		0	0
Dividends payable		53.6	0
Customer deposits		18.8	17.9
Taxes accrued		101	106
Interest accrued		37.2	9.5
Exchange gas payable		12.1	18.6
Deferred revenue		10.5	15
Accrued capital expenditures		88.7	100.1
Accrued compensation and related costs		28.5	51.9
Other accruals		89.9	70
Total Current Liabilities		514	460.8
Noncurrent Liabilities
Long-term debt		2,725.9	2,725.6
Long-term debt-affiliated		0	0
Deferred income taxes		1,395.3	1,348.1
Accrued liability for postretirement and postemployment benefits		48.9	49.4
Regulatory liabilities		303.6	321.6
Asset retirement obligations		25.1	25.7	23.5	23.2
Other noncurrent liabilities		94.4	91.4
Total Noncurrent Liabilities		4,593.2	4,561.8
Total Liabilities		5,107.2	5,022.6
Equity
Common stock, $0.01 par value, 2,000,000,000 shares authorized; 400,383,243 and 399,841,350 shares outstanding, respectively		4	4
Additional paid-in capital		4,037.1	4,032.7
Retained earnings		14	46.9
Net parent investment		0	0
Treasury stock		(6)	0
Accumulated other comprehensive loss	[1]	(26.6)	(27)	(25.1)	(34.5)
Total CPG Equity		4,022.5	4,056.6
Noncontrolling Interest		961.4	956.4
Total Equity		4,983.9	5,013	4,949	4,176.3
Total Liabilities and Equity		10,091.1	10,035.6
Consolidating adjustments and eliminations
Current Assets
Cash and cash equivalents		0	0	0	0
Accounts receivable, net		0	0
Accounts receivable-affiliated		(434.3)	(260)
Materials and supplies, at average cost		0	0
Exchange gas receivable		0	0
Deferred property taxes		0	0
Prepayments and other		(9.3)	(5.7)
Total Current Assets		(443.6)	(265.7)
Investments
Unconsolidated affiliates		0	0
Consolidated affiliates		(18,694)	(18,353.3)
Other investments		0	0
Total Investments		(18,694)	(18,353.3)
Property, Plant and Equipment
Property, plant and equipment		0	0
Accumulated depreciation and amortization		0	0
Net Property, Plant and Equipment		0	0
Other Noncurrent Assets
Regulatory assets		0	0
Goodwill		0	0
Notes receivable-affiliated		(1,848.2)	(1,848.2)
Postretirement and postemployment benefits assets		(0.4)	(0.4)
Deferred income taxes		(23.3)	(18.9)
Deferred charges and other		0	0
Total Other Noncurrent Assets		(1,871.9)	(1,867.5)
Total Assets		(21,009.5)	(20,486.5)
Current Liabilities
Short-term borrowings		0	0
Short-term borrowings-affiliated		(407.9)	(233.3)
Accounts payable		0	0
Accounts payable-affiliated		(26.4)	(26.7)
Dividends payable		0
Customer deposits		0	0
Taxes accrued		(9.3)	(5.7)
Interest accrued		0	0
Exchange gas payable		0	0
Deferred revenue		0	0
Accrued capital expenditures		0	0
Accrued compensation and related costs		0	0
Other accruals		0	0
Total Current Liabilities		(443.6)	(265.7)
Noncurrent Liabilities
Long-term debt		0	0
Long-term debt-affiliated		(1,848.2)	(1,848.2)
Deferred income taxes		(23.3)	(18.9)
Accrued liability for postretirement and postemployment benefits		(0.4)	(0.4)
Regulatory liabilities		0	0
Asset retirement obligations		0	0
Other noncurrent liabilities		0	0
Total Noncurrent Liabilities		(1,871.9)	(1,867.5)
Total Liabilities		(2,315.5)	(2,133.2)
Equity
Common stock, $0.01 par value, 2,000,000,000 shares authorized; 400,383,243 and 399,841,350 shares outstanding, respectively		0	0
Additional paid-in capital		0	0
Retained earnings		0	0
Net parent investment		(17,812.9)	(17,479)
Treasury stock		0
Accumulated other comprehensive loss		80.3	82.1
Total CPG Equity		(17,732.6)	(17,396.9)
Noncontrolling Interest		(961.4)	(956.4)
Total Equity		(18,694)	(18,353.3)
Total Liabilities and Equity		(21,009.5)	(20,486.5)
Columbia Pipeline Group
Current Assets
Cash and cash equivalents		549.2	800	0	0
Accounts receivable, net		0.5	0
Accounts receivable-affiliated		105.4	14.6
Materials and supplies, at average cost		0	0
Exchange gas receivable		0	0
Deferred property taxes		0	0
Prepayments and other		9.3	0.3
Total Current Assets		664.4	814.9
Investments
Unconsolidated affiliates		0	0
Consolidated affiliates		5,278.9	5,174.6
Other investments		12	12
Total Investments		5,290.9	5,186.6
Property, Plant and Equipment
Property, plant and equipment		0	0
Accumulated depreciation and amortization		0	0
Net Property, Plant and Equipment		0	0
Other Noncurrent Assets
Regulatory assets		0	0
Goodwill		0	0
Notes receivable-affiliated		1,848.2	1,848.2
Postretirement and postemployment benefits assets		0	0
Deferred income taxes		23.3	18.9
Deferred charges and other		4.6	4.9
Total Other Noncurrent Assets		1,876.1	1,872
Total Assets		7,831.4	7,873.5
Current Liabilities
Short-term borrowings		0	0
Short-term borrowings-affiliated		0	99
Accounts payable		11	0.1
Accounts payable-affiliated		7.8	10.8
Dividends payable		53.6
Customer deposits		0	0
Taxes accrued		0	0
Interest accrued		37	9.4
Exchange gas payable		0	0
Deferred revenue		0	0
Accrued capital expenditures		0	0
Accrued compensation and related costs		0	0
Other accruals		0.3	0
Total Current Liabilities		109.7	119.3
Noncurrent Liabilities
Long-term debt		2,725.9	2,725.6
Long-term debt-affiliated		0	0
Deferred income taxes		0	0
Accrued liability for postretirement and postemployment benefits		0.3	0.3
Regulatory liabilities		0	0
Asset retirement obligations		0	0
Other noncurrent liabilities		11.6	15.3
Total Noncurrent Liabilities		2,737.8	2,741.2
Total Liabilities		2,847.5	2,860.5
Equity
Common stock, $0.01 par value, 2,000,000,000 shares authorized; 400,383,243 and 399,841,350 shares outstanding, respectively		4	4
Additional paid-in capital		4,037.1	4,032.7
Retained earnings		14	46.9
Net parent investment		0	0
Treasury stock		(6)
Accumulated other comprehensive loss		(26.6)	(27)
Total CPG Equity		4,022.5	4,056.6
Noncontrolling Interest		961.4	956.4
Total Equity		4,983.9	5,013
Total Liabilities and Equity		7,831.4	7,873.5
Columbia Energy Group
Current Assets
Cash and cash equivalents		53.8	46.7	0	0
Accounts receivable, net		5.6	5.6
Accounts receivable-affiliated		193.4	85.6
Materials and supplies, at average cost		0	0
Exchange gas receivable		0	0
Deferred property taxes		0	0
Prepayments and other		4.6	10.1
Total Current Assets		257.4	148
Investments
Unconsolidated affiliates		0	0
Consolidated affiliates		7,624.1	7,569.8
Other investments		0.3	0.3
Total Investments		7,624.4	7,570.1
Property, Plant and Equipment
Property, plant and equipment		0	0
Accumulated depreciation and amortization		0	0
Net Property, Plant and Equipment		0	0
Other Noncurrent Assets
Regulatory assets		41.1	35.1
Goodwill		0	0
Notes receivable-affiliated		0	0
Postretirement and postemployment benefits assets		0.6	0.5
Deferred income taxes		0	0
Deferred charges and other		0	0
Total Other Noncurrent Assets		41.7	35.6
Total Assets		7,923.5	7,753.7
Current Liabilities
Short-term borrowings		0	0
Short-term borrowings-affiliated		0	0
Accounts payable		0	0
Accounts payable-affiliated		14.9	4.8
Dividends payable		0
Customer deposits		0	0
Taxes accrued		10.6	0
Interest accrued		0	0
Exchange gas payable		0	0
Deferred revenue		0	0
Accrued capital expenditures		0	0
Accrued compensation and related costs		0	0
Other accruals		0.3	0.3
Total Current Liabilities		25.8	5.1
Noncurrent Liabilities
Long-term debt		0	0
Long-term debt-affiliated		1,217.3	1,217.3
Deferred income taxes		1,396.7	1,350.4
Accrued liability for postretirement and postemployment benefits		7.8	8.3
Regulatory liabilities		10.4	10.5
Asset retirement obligations		0	0
Other noncurrent liabilities		0.3	0.2
Total Noncurrent Liabilities		2,632.5	2,586.7
Total Liabilities		2,658.3	2,591.8
Equity
Common stock, $0.01 par value, 2,000,000,000 shares authorized; 400,383,243 and 399,841,350 shares outstanding, respectively		0	0
Additional paid-in capital		0	0
Retained earnings		0	0
Net parent investment		4,330.2	4,232.3
Treasury stock		0
Accumulated other comprehensive loss		(26.4)	(26.8)
Total CPG Equity		4,303.8	4,205.5
Noncontrolling Interest		961.4	956.4
Total Equity		5,265.2	5,161.9
Total Liabilities and Equity		7,923.5	7,753.7
Columbia OpCo
Current Assets
Cash and cash equivalents		0	1.9	2.2	0
Accounts receivable, net		0	0
Accounts receivable-affiliated		0	3.4
Materials and supplies, at average cost		0	0
Exchange gas receivable		0	0
Deferred property taxes		0	0
Prepayments and other		0	0
Total Current Assets		0	5.3
Investments
Unconsolidated affiliates		0	0
Consolidated affiliates		5,791	5,608.9
Other investments		0	0
Total Investments		5,791	5,608.9
Property, Plant and Equipment
Property, plant and equipment		0	0
Accumulated depreciation and amortization		0	0
Net Property, Plant and Equipment		0	0
Other Noncurrent Assets
Regulatory assets		0	0
Goodwill		1,975.5	1,975.5
Notes receivable-affiliated		0	0
Postretirement and postemployment benefits assets		0	0
Deferred income taxes		0	0
Deferred charges and other		0	0
Total Other Noncurrent Assets		1,975.5	1,975.5
Total Assets		7,766.5	7,589.7
Current Liabilities
Short-term borrowings		0	0
Short-term borrowings-affiliated		124	0
Accounts payable		0	0
Accounts payable-affiliated		0.1	0
Dividends payable		0
Customer deposits		0	0
Taxes accrued		0	0
Interest accrued		0	0
Exchange gas payable		0	0
Deferred revenue		0	0
Accrued capital expenditures		0	0
Accrued compensation and related costs		0	0
Other accruals		0	0
Total Current Liabilities		124.1	0
Noncurrent Liabilities
Long-term debt		0	0
Long-term debt-affiliated		0	0
Deferred income taxes		0	0
Accrued liability for postretirement and postemployment benefits		0	0
Regulatory liabilities		0	0
Asset retirement obligations		0	0
Other noncurrent liabilities		0	0
Total Noncurrent Liabilities		0	0
Total Liabilities		124.1	0
Equity
Common stock, $0.01 par value, 2,000,000,000 shares authorized; 400,383,243 and 399,841,350 shares outstanding, respectively		0	0
Additional paid-in capital		0	0
Retained earnings		0	0
Net parent investment		7,667.3	7,615.4
Treasury stock		0
Accumulated other comprehensive loss		(24.9)	(25.7)
Total CPG Equity		7,642.4	7,589.7
Noncontrolling Interest		0	0
Total Equity		7,642.4	7,589.7
Total Liabilities and Equity		7,766.5	7,589.7
CPG OpCo GP
Current Assets
Cash and cash equivalents		0	0	0	0
Accounts receivable, net		0	0
Accounts receivable-affiliated		0	0
Materials and supplies, at average cost		0	0
Exchange gas receivable		0	0
Deferred property taxes		0	0
Prepayments and other		0	0
Total Current Assets		0	0
Investments
Unconsolidated affiliates		0	0
Consolidated affiliates		0	0
Other investments		0	0
Total Investments		0	0
Property, Plant and Equipment
Property, plant and equipment		0	0
Accumulated depreciation and amortization		0	0
Net Property, Plant and Equipment		0	0
Other Noncurrent Assets
Regulatory assets		0	0
Goodwill		0	0
Notes receivable-affiliated		0	0
Postretirement and postemployment benefits assets		0	0
Deferred income taxes		0	0
Deferred charges and other		0	0
Total Other Noncurrent Assets		0	0
Total Assets		0	0
Current Liabilities
Short-term borrowings		0	0
Short-term borrowings-affiliated		0	0
Accounts payable		0	0
Accounts payable-affiliated		0	0
Dividends payable		0
Customer deposits		0	0
Taxes accrued		0	0
Interest accrued		0	0
Exchange gas payable		0	0
Deferred revenue		0	0
Accrued capital expenditures		0	0
Accrued compensation and related costs		0	0
Other accruals		0	0
Total Current Liabilities		0	0
Noncurrent Liabilities
Long-term debt		0	0
Long-term debt-affiliated		0	0
Deferred income taxes		0	0
Accrued liability for postretirement and postemployment benefits		0	0
Regulatory liabilities		0	0
Asset retirement obligations		0	0
Other noncurrent liabilities		0	0
Total Noncurrent Liabilities		0	0
Total Liabilities		0	0
Equity
Common stock, $0.01 par value, 2,000,000,000 shares authorized; 400,383,243 and 399,841,350 shares outstanding, respectively		0	0
Additional paid-in capital		0	0
Retained earnings		0	0
Net parent investment		0	0
Treasury stock		0
Accumulated other comprehensive loss		0	0
Total CPG Equity		0	0
Noncontrolling Interest		0	0
Total Equity		0	0
Total Liabilities and Equity		0	0
Non-Guarantor Subsidiaries
Current Assets
Cash and cash equivalents		37.9	82.3	$ 5.1	$ 0.5
Accounts receivable, net		155.4	146.8
Accounts receivable-affiliated		135.5	156.4
Materials and supplies, at average cost		33.2	32.8
Exchange gas receivable		12	19
Deferred property taxes		54.2	52
Prepayments and other		41.9	43.8
Total Current Assets		470.1	533.1
Investments
Unconsolidated affiliates		437.3	438.1
Consolidated affiliates		0	0
Other investments		1.5	1.5
Total Investments		438.8	439.6
Property, Plant and Equipment
Property, plant and equipment		9,426	9,052.3
Accumulated depreciation and amortization		(3,025.1)	(2,988.6)
Net Property, Plant and Equipment		6,400.9	6,063.7
Other Noncurrent Assets
Regulatory assets		141.1	142.6
Goodwill		0	0
Notes receivable-affiliated		0	0
Postretirement and postemployment benefits assets		117.5	115.6
Deferred income taxes		0	0
Deferred charges and other		10.8	10.6
Total Other Noncurrent Assets		269.4	268.8
Total Assets		7,579.2	7,305.2
Current Liabilities
Short-term borrowings		15	15
Short-term borrowings-affiliated		283.9	134.3
Accounts payable		47.7	56.7
Accounts payable-affiliated		3.6	11.1
Dividends payable		0
Customer deposits		18.8	17.9
Taxes accrued		99.7	111.7
Interest accrued		0.2	0.1
Exchange gas payable		12.1	18.6
Deferred revenue		10.5	15
Accrued capital expenditures		88.7	100.1
Accrued compensation and related costs		28.5	51.9
Other accruals		89.3	69.7
Total Current Liabilities		698	602.1
Noncurrent Liabilities
Long-term debt		0	0
Long-term debt-affiliated		630.9	630.9
Deferred income taxes		21.9	16.6
Accrued liability for postretirement and postemployment benefits		41.2	41.2
Regulatory liabilities		293.2	311.1
Asset retirement obligations		25.1	25.7
Other noncurrent liabilities		82.5	75.9
Total Noncurrent Liabilities		1,094.8	1,101.4
Total Liabilities		1,792.8	1,703.5
Equity
Common stock, $0.01 par value, 2,000,000,000 shares authorized; 400,383,243 and 399,841,350 shares outstanding, respectively		0	0
Additional paid-in capital		0	0
Retained earnings		0	0
Net parent investment		5,815.4	5,631.3
Treasury stock		0
Accumulated other comprehensive loss		(29)	(29.6)
Total CPG Equity		5,786.4	5,601.7
Noncontrolling Interest		0	0
Total Equity		5,786.4	5,601.7
Total Liabilities and Equity		$ 7,579.2	$ 7,305.2
[1]	All amounts are net of tax. Amounts in parentheses indicate debits.

Condensed Consolidating Finan76

Condensed Consolidating Financial Statements (Condensed Consolidating Statements of Operations) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Operating Revenues
Transportation revenues	$ 308.5	$ 248.4
Transportation revenues-affiliated	0	29
Storage revenues	49.9	36.6
Storage revenues-affiliated	0	13.3
Other revenues	6.1	12.7
Total Operating Revenues	364.5	340
Operating Expenses
Operation and maintenance	169.1	118.4
Operation and maintenance-affiliated	0	28
Depreciation and amortization	40.4	32.5
Gain on sale of assets	(2.6)	(5.3)
Property and other taxes	21.8	19.1
Total Operating Expenses	228.7	192.7
Equity Earnings in Unconsolidated Affiliates	15.9	15.4
Equity Earnings in Consolidated Affiliates	0	0
Operating Income	151.7	162.7
Other Income (Deductions)
Interest expense	(29.4)	0
Interest expense-affiliated	0	(18.3)
Other, net	7	4.6
Total Other Deductions, net	(22.4)	(13.7)
Income from Continuing Operations before Income Taxes	129.3	149
Income Taxes	42.7	51.9
Income from Continuing Operations	86.6	97.1
Income from Discontinued Operations-net of taxes	0.2	0
Net Income	86.8	97.1
Less: Net income attributable to noncontrolling interest	14.6	7.1
Net income attributable to CPG	72.2	90
Consolidating adjustments and eliminations
Operating Revenues
Transportation revenues	0	0
Transportation revenues-affiliated	0	0
Storage revenues	0	0
Storage revenues-affiliated	0	0
Other revenues	0	0
Total Operating Revenues	0	0
Operating Expenses
Operation and maintenance	(0.2)	0
Operation and maintenance-affiliated	(0.1)	0
Depreciation and amortization	0	0
Gain on sale of assets	0	0
Property and other taxes	0	0
Total Operating Expenses	(0.3)	0
Equity Earnings in Unconsolidated Affiliates	0	0
Equity Earnings in Consolidated Affiliates	(474.8)	(359.5)
Operating Income	(474.5)	(359.5)
Other Income (Deductions)
Interest expense	0.7
Interest expense-affiliated	18.5	0
Other, net	(19.2)	0
Total Other Deductions, net	0	0
Income from Continuing Operations before Income Taxes	(474.5)	(359.5)
Income Taxes	(1.1)	0
Income from Continuing Operations	(473.4)
Income from Discontinued Operations-net of taxes	(0.2)
Net Income	(473.6)	(359.5)
Less: Net income attributable to noncontrolling interest	(14.6)	(7.1)
Net income attributable to CPG	(459)	(352.4)
Columbia Pipeline Group
Operating Revenues
Transportation revenues	0	0
Transportation revenues-affiliated	0	0
Storage revenues	0	0
Storage revenues-affiliated	0	0
Other revenues	0	0
Total Operating Revenues	0	0
Operating Expenses
Operation and maintenance	30.4	0
Operation and maintenance-affiliated	0.1	0
Depreciation and amortization	0	0
Gain on sale of assets	0	0
Property and other taxes	0.1	0
Total Operating Expenses	30.6	0
Equity Earnings in Unconsolidated Affiliates	0	0
Equity Earnings in Consolidated Affiliates	113.5	97.1
Operating Income	82.9	97.1
Other Income (Deductions)
Interest expense	(29.5)
Interest expense-affiliated	0	0
Other, net	19.7	0
Total Other Deductions, net	(9.8)	0
Income from Continuing Operations before Income Taxes	73.1	97.1
Income Taxes	(13.5)	0
Income from Continuing Operations	86.6
Income from Discontinued Operations-net of taxes	0.2
Net Income	86.8	97.1
Less: Net income attributable to noncontrolling interest	14.6	7.1
Net income attributable to CPG	72.2	90
Columbia Energy Group
Operating Revenues
Transportation revenues	0	0
Transportation revenues-affiliated	0	0
Storage revenues	0	0
Storage revenues-affiliated	0	0
Other revenues	0	0
Total Operating Revenues	0	0
Operating Expenses
Operation and maintenance	(0.2)	(0.1)
Operation and maintenance-affiliated	0	0.1
Depreciation and amortization	0.2	0
Gain on sale of assets	0	0
Property and other taxes	0	0
Total Operating Expenses	0	0
Equity Earnings in Unconsolidated Affiliates	0	0
Equity Earnings in Consolidated Affiliates	179.8	131.2
Operating Income	179.8	131.2
Other Income (Deductions)
Interest expense	0
Interest expense-affiliated	(11.2)	(6.9)
Other, net	0.5	0.4
Total Other Deductions, net	(10.7)	(6.5)
Income from Continuing Operations before Income Taxes	169.1	124.7
Income Taxes	56.8	27.6
Income from Continuing Operations	112.3
Income from Discontinued Operations-net of taxes	0.2
Net Income	112.5	97.1
Less: Net income attributable to noncontrolling interest	14.6	7.1
Net income attributable to CPG	97.9	90
Columbia OpCo
Operating Revenues
Transportation revenues	0	0
Transportation revenues-affiliated	0	0
Storage revenues	0	0
Storage revenues-affiliated	0	0
Other revenues	0	0
Total Operating Revenues	0	0
Operating Expenses
Operation and maintenance	0	0
Operation and maintenance-affiliated	0	0
Depreciation and amortization	0	0
Gain on sale of assets	0	0
Property and other taxes	0	0
Total Operating Expenses	0	0
Equity Earnings in Unconsolidated Affiliates	0	0
Equity Earnings in Consolidated Affiliates	181.5	131.2
Operating Income	181.5	131.2
Other Income (Deductions)
Interest expense	0
Interest expense-affiliated	(0.1)	0
Other, net	0	0.7
Total Other Deductions, net	(0.1)	0.7
Income from Continuing Operations before Income Taxes	181.4	131.9
Income Taxes	0	0
Income from Continuing Operations	181.4
Income from Discontinued Operations-net of taxes	0
Net Income	181.4	131.9
Less: Net income attributable to noncontrolling interest	0	0
Net income attributable to CPG	181.4	131.9
CPG OpCo GP
Operating Revenues
Transportation revenues	0	0
Transportation revenues-affiliated	0	0
Storage revenues	0	0
Storage revenues-affiliated	0	0
Other revenues	0	0
Total Operating Revenues	0	0
Operating Expenses
Operation and maintenance	0	0
Operation and maintenance-affiliated	0	0
Depreciation and amortization	0	0
Gain on sale of assets	0	0
Property and other taxes	0	0
Total Operating Expenses	0	0
Equity Earnings in Unconsolidated Affiliates	0	0
Equity Earnings in Consolidated Affiliates	0	0
Operating Income	0	0
Other Income (Deductions)
Interest expense	0
Interest expense-affiliated	0	0
Other, net	0	0
Total Other Deductions, net	0	0
Income from Continuing Operations before Income Taxes	0	0
Income Taxes	0	0
Income from Continuing Operations	0
Income from Discontinued Operations-net of taxes	0
Net Income	0	0
Less: Net income attributable to noncontrolling interest	0	0
Net income attributable to CPG	0	0
Non-Guarantor Subsidiaries
Operating Revenues
Transportation revenues	308.5	248.4
Transportation revenues-affiliated	0	29
Storage revenues	49.9	36.6
Storage revenues-affiliated	0	13.3
Other revenues	6.1	12.7
Total Operating Revenues	364.5	340
Operating Expenses
Operation and maintenance	139.1	118.5
Operation and maintenance-affiliated	0	27.9
Depreciation and amortization	40.2	32.5
Gain on sale of assets	(2.6)	(5.3)
Property and other taxes	21.7	19.1
Total Operating Expenses	198.4	192.7
Equity Earnings in Unconsolidated Affiliates	15.9	15.4
Equity Earnings in Consolidated Affiliates	0	0
Operating Income	182	162.7
Other Income (Deductions)
Interest expense	(0.6)
Interest expense-affiliated	(7.2)	(11.4)
Other, net	6	3.5
Total Other Deductions, net	(1.8)	(7.9)
Income from Continuing Operations before Income Taxes	180.2	154.8
Income Taxes	0.5	24.3
Income from Continuing Operations	179.7
Income from Discontinued Operations-net of taxes	0
Net Income	179.7	130.5
Less: Net income attributable to noncontrolling interest	0	0
Net income attributable to CPG	$ 179.7	$ 130.5

Condensed Consolidating Finan77

Condensed Consolidating Financial Statements (Condensed Statements of Comprehensive Income) (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2016	Mar. 31, 2015
Condensed Statement of Income Captions [Line Items]
Net Income		$ 86.8	$ 97.1
Net unrealized gain on cash flow hedges	[1]	0.4	0.2
Unrecognized pension and OPEB benefit	[2],[3]	0.1	7
Total other comprehensive income	[4]	0.5	7.2
Total comprehensive income		87.3	104.3
Less: Comprehensive Income-noncontrolling interest		14.7	7.1
Comprehensive Income-controlling interests		72.6	97.2
Consolidating adjustments and eliminations
Condensed Statement of Income Captions [Line Items]
Net Income		(473.6)	(359.5)
Net unrealized gain on cash flow hedges		(0.4)	(0.2)
Unrecognized pension and OPEB benefit		(0.1)	(7)
Total other comprehensive income		(0.5)	(7.2)
Total comprehensive income		(474.1)	(366.7)
Less: Comprehensive Income-noncontrolling interest		(14.7)	(7.1)
Comprehensive Income-controlling interests		(459.4)	(359.6)
Columbia Pipeline Group
Condensed Statement of Income Captions [Line Items]
Net Income		86.8	97.1
Net unrealized gain on cash flow hedges		0.4	0.2
Unrecognized pension and OPEB benefit		0.1	7
Total other comprehensive income		0.5	7.2
Total comprehensive income		87.3	104.3
Less: Comprehensive Income-noncontrolling interest		14.7	7.1
Comprehensive Income-controlling interests		72.6	97.2
Columbia Energy Group
Condensed Statement of Income Captions [Line Items]
Net Income		112.5	97.1
Net unrealized gain on cash flow hedges		(0.1)	(0.1)
Unrecognized pension and OPEB benefit		0.1	7
Total other comprehensive income		0	6.9
Total comprehensive income		112.5	104
Less: Comprehensive Income-noncontrolling interest		14.7	7.1
Comprehensive Income-controlling interests		97.8	96.9
Columbia OpCo
Condensed Statement of Income Captions [Line Items]
Net Income		181.4	131.9
Net unrealized gain on cash flow hedges		0	0
Unrecognized pension and OPEB benefit		0	0
Total other comprehensive income		0	0
Total comprehensive income		181.4	131.9
Less: Comprehensive Income-noncontrolling interest		0	0
Comprehensive Income-controlling interests		181.4	131.9
CPG OpCo GP
Condensed Statement of Income Captions [Line Items]
Net Income		0	0
Net unrealized gain on cash flow hedges		0	0
Unrecognized pension and OPEB benefit		0	0
Total other comprehensive income		0	0
Total comprehensive income		0	0
Less: Comprehensive Income-noncontrolling interest		0	0
Comprehensive Income-controlling interests		0	0
Non-Guarantor Subsidiaries
Condensed Statement of Income Captions [Line Items]
Net Income		179.7	130.5
Net unrealized gain on cash flow hedges		0.5	0.3
Unrecognized pension and OPEB benefit		0	0
Total other comprehensive income		0.5	0.3
Total comprehensive income		180.2	130.8
Less: Comprehensive Income-noncontrolling interest		0	0
Comprehensive Income-controlling interests		$ 180.2	$ 130.8
[1]	Net unrealized gains on derivatives qualifying as cash flow hedges, net of $0.2 million and $0.1 million tax expense for the three months ended March 31, 2016 and 2015, respectively.
[2]	Unrecognized pension and OPEB benefits are primarily related to pension and OPEB remeasurements recorded during 2016 and 2015.
[3]	Unrecognized pension and other postretirement benefit (“OPEB”) benefits, net of $0.1 million and zero tax expense for the three months ended March 31, 2016 and 2015, respectively.
[4]	All amounts are net of tax. Amounts in parentheses indicate debits.

Condensed Consolidating Finan78

Condensed Consolidating Financial Statements (Condensed Consolidating Statements of Cash Flows) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Net Cash Provided by (Used in) Operating Activities [Abstract]
Net Cash Provided by (Used in) Operating Activities	$ 170.3	$ 163.8
Investing Activities
Capital expenditures	(388.9)	(163.9)
Change in short-term lendings-affiliated	0	(698)
Proceeds from disposition of assets	0	10.2
Contributions to equity investees	(1.9)	0
Distributions from equity investees	0.2	1.3
Other investing activities	(2)	(2.4)
Net Cash Flows used for Investing Activities	(392.6)	(852.8)
Financing Activities
Change in short-term borrowings-affiliated	0	(232.1)
Debt related costs	(0.5)	0
Issuance of long-term debt-affiliated	0	1,217.3
Payments of long-term debt-affiliated, including current portion	0	(957.8)
Proceeds from the issuance of common units, net of offering costs	0	1,168.4
Contribution of capital from parent		0
Distribution of IPO proceeds to parent	0	(500)
Quarterly distributions to unitholders	0
Distribution to noncontrolling interest in Columbia OpCo	0
Distribution to noncontrolling interest	(9.7)	0
Acquisition of treasury stock	(6)	0
Dividends paid - common stock	(51.5)	0
Net Cash Flows (used for) from Financing Activities	(67.7)	695.8
Change in cash and cash equivalents	(290)	6.8
Cash and cash equivalents at beginning of period	930.9	0.5
Cash and Cash Equivalents at End of Period	640.9	7.3
Consolidating adjustments and eliminations
Net Cash Provided by (Used in) Operating Activities [Abstract]
Net Cash Provided by (Used in) Operating Activities	(137.6)	0
Investing Activities
Capital expenditures	0	0
Change in short-term lendings-affiliated	174.5	0
Proceeds from disposition of assets		0
Contributions to equity investees	0	1,217.3
Distributions from equity investees	0	0
Other investing activities	0	0
Net Cash Flows used for Investing Activities	174.5	1,217.3
Financing Activities
Change in short-term borrowings-affiliated	(174.5)	0
Debt related costs	0
Issuance of long-term debt-affiliated		0
Payments of long-term debt-affiliated, including current portion		0
Proceeds from the issuance of common units, net of offering costs		0
Contribution of capital from parent		(1,217.3)
Distribution of IPO proceeds to parent		0
Quarterly distributions to unitholders	18.1
Distribution to noncontrolling interest in Columbia OpCo	129.2
Distribution to noncontrolling interest	(9.7)
Acquisition of treasury stock	0
Dividends paid - common stock	0
Net Cash Flows (used for) from Financing Activities	(36.9)	(1,217.3)
Change in cash and cash equivalents	0	0
Cash and cash equivalents at beginning of period	0	0
Cash and Cash Equivalents at End of Period	0	0
Columbia Pipeline Group
Net Cash Provided by (Used in) Operating Activities [Abstract]
Net Cash Provided by (Used in) Operating Activities	(6.7)	(4.6)
Investing Activities
Capital expenditures	0	0
Change in short-term lendings-affiliated	(87.1)	0
Proceeds from disposition of assets		0
Contributions to equity investees	0	0
Distributions from equity investees	0	0
Other investing activities	0	0
Net Cash Flows used for Investing Activities	(87.1)	0
Financing Activities
Change in short-term borrowings-affiliated	(99)	4.6
Debt related costs	(0.5)
Issuance of long-term debt-affiliated		0
Payments of long-term debt-affiliated, including current portion		0
Proceeds from the issuance of common units, net of offering costs		0
Contribution of capital from parent		0
Distribution of IPO proceeds to parent		0
Quarterly distributions to unitholders	0
Distribution to noncontrolling interest in Columbia OpCo	0
Distribution to noncontrolling interest	0
Acquisition of treasury stock	(6)
Dividends paid - common stock	(51.5)
Net Cash Flows (used for) from Financing Activities	(157)	4.6
Change in cash and cash equivalents	(250.8)	0
Cash and cash equivalents at beginning of period	800	0
Cash and Cash Equivalents at End of Period	549.2	0
Columbia Energy Group
Net Cash Provided by (Used in) Operating Activities [Abstract]
Net Cash Provided by (Used in) Operating Activities	116.4	(3.9)
Investing Activities
Capital expenditures	0	0
Change in short-term lendings-affiliated	(109.3)	0
Proceeds from disposition of assets		0
Contributions to equity investees	0	(1,217.3)
Distributions from equity investees	0	0
Other investing activities	0	0
Net Cash Flows used for Investing Activities	(109.3)	(1,217.3)
Financing Activities
Change in short-term borrowings-affiliated	0	3.9
Debt related costs	0
Issuance of long-term debt-affiliated		1,217.3
Payments of long-term debt-affiliated, including current portion		0
Proceeds from the issuance of common units, net of offering costs		0
Contribution of capital from parent		0
Distribution of IPO proceeds to parent		0
Quarterly distributions to unitholders	0
Distribution to noncontrolling interest in Columbia OpCo	0
Distribution to noncontrolling interest	0
Acquisition of treasury stock	0
Dividends paid - common stock	0
Net Cash Flows (used for) from Financing Activities	0	1,221.2
Change in cash and cash equivalents	7.1	0
Cash and cash equivalents at beginning of period	46.7	0
Cash and Cash Equivalents at End of Period	53.8	0
Columbia OpCo
Net Cash Provided by (Used in) Operating Activities [Abstract]
Net Cash Provided by (Used in) Operating Activities	0	0.3
Investing Activities
Capital expenditures	0	0
Change in short-term lendings-affiliated	3.3	(668.1)
Proceeds from disposition of assets		0
Contributions to equity investees	0	0
Distributions from equity investees	0	0
Other investing activities	0	0
Net Cash Flows used for Investing Activities	3.3	(668.1)
Financing Activities
Change in short-term borrowings-affiliated	124	0
Debt related costs	0
Issuance of long-term debt-affiliated		0
Payments of long-term debt-affiliated, including current portion		0
Proceeds from the issuance of common units, net of offering costs		1,170
Contribution of capital from parent		0
Distribution of IPO proceeds to parent		(500)
Quarterly distributions to unitholders	0
Distribution to noncontrolling interest in Columbia OpCo	(129.2)
Distribution to noncontrolling interest	0
Acquisition of treasury stock	0
Dividends paid - common stock	0
Net Cash Flows (used for) from Financing Activities	(5.2)	670
Change in cash and cash equivalents	(1.9)	2.2
Cash and cash equivalents at beginning of period	1.9	0
Cash and Cash Equivalents at End of Period	0	2.2
CPG OpCo GP
Net Cash Provided by (Used in) Operating Activities [Abstract]
Net Cash Provided by (Used in) Operating Activities	0	0
Investing Activities
Capital expenditures	0	0
Change in short-term lendings-affiliated	0	0
Proceeds from disposition of assets		0
Contributions to equity investees	0	0
Distributions from equity investees	0	0
Other investing activities	0	0
Net Cash Flows used for Investing Activities	0	0
Financing Activities
Change in short-term borrowings-affiliated	0	0
Debt related costs	0
Issuance of long-term debt-affiliated		0
Payments of long-term debt-affiliated, including current portion		0
Proceeds from the issuance of common units, net of offering costs		0
Contribution of capital from parent		0
Distribution of IPO proceeds to parent		0
Quarterly distributions to unitholders	0
Distribution to noncontrolling interest in Columbia OpCo	0
Distribution to noncontrolling interest	0
Acquisition of treasury stock	0
Dividends paid - common stock	0
Net Cash Flows (used for) from Financing Activities	0	0
Change in cash and cash equivalents	0	0
Cash and cash equivalents at beginning of period	0	0
Cash and Cash Equivalents at End of Period	0	0
Non-Guarantor Subsidiaries
Net Cash Provided by (Used in) Operating Activities [Abstract]
Net Cash Provided by (Used in) Operating Activities	198.2	172
Investing Activities
Capital expenditures	(388.9)	(163.9)
Change in short-term lendings-affiliated	18.6	(29.9)
Proceeds from disposition of assets		10.2
Contributions to equity investees	(1.9)	0
Distributions from equity investees	0.2	1.3
Other investing activities	(2)	(2.4)
Net Cash Flows used for Investing Activities	(374)	(184.7)
Financing Activities
Change in short-term borrowings-affiliated	149.5	(240.6)
Debt related costs	0
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		(1.6)
Contribution of capital from parent		1,217.3
Distribution of IPO proceeds to parent		0
Quarterly distributions to unitholders	(18.1)
Distribution to noncontrolling interest in Columbia OpCo	0
Distribution to noncontrolling interest	0
Acquisition of treasury stock	0
Dividends paid - common stock	0
Net Cash Flows (used for) from Financing Activities	131.4	17.3
Change in cash and cash equivalents	(44.4)	4.6
Cash and cash equivalents at beginning of period	82.3	0.5
Cash and Cash Equivalents at End of Period	$ 37.9	$ 5.1