Columbia Pipeline (CPGX) 10-K 18 Feb 16 2015 FY Annual report Financial data

Document And Entity Information

Document And Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2015	Feb. 10, 2016	Jun. 30, 2015
Document Information [Line Items]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2015
Document Fiscal Year Focus	2,015
Document Fiscal Period Focus	FY
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 Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float			$ 0
Entity Common Stock, Shares Outstanding		399,841,350

Statements of Consolidated and

Statements of Consolidated and Combined Balance Sheets - USD ($) $ in Millions		Dec. 31, 2015	Dec. 31, 2014
Current Assets
Cash and cash equivalents		$ 930.9	$ 0.5
Accounts receivable (less reserve of $0.6 and $0.6, respectively)		152.4	149.4
Accounts receivable-affiliated		0	180
Materials and supplies, at average cost		32.8	24.9
Exchange gas receivable		19	34.8
Deferred Property Taxes		52	48.9
Deferred income taxes		0	60
Prepayments and other		48.5	20.8
Total Current Assets		1,235.6	519.3
Investments
Unconsolidated affiliates		438.1	444.3
Other investments		13.8	2.7
Total Investments		451.9	447
Property, Plant and Equipment
Property, plant and equipment		9,052.3	7,935.4
Accumulated depreciation and amortization		(2,988.6)	(2,976.8)
Net Property, Plant and Equipment		6,063.7	4,958.6
Other Noncurrent Assets
Regulatory assets		177.7	151.9
Goodwill		1,975.5	1,975.5
Postretirement and postemployment benefits assets		115.7	90
Deferred charges and other		36.1	15.2
Total Other Noncurrent Assets		2,305	2,232.6
Total Assets		10,056.2	8,157.5
Current Liabilities
Current portion of long-term debt-affiliated		0	115.9
Short-term borrowings		15	0
Short-term borrowings-affiliated		0	252.5
Accounts payable		56.8	56
Accounts payable-affiliated		0	53.6
Customer deposits		17.9	13.4
Taxes accrued		106	103.2
Interest accrued		9.5	0
Exchange gas payable		18.6	34.7
Deferred revenue		15	22.5
Accrued capital expenditures		100.1	61.1
Accrued compensation and related costs		51.9	31.2
Other accruals		70	40.1
Total Current Liabilities		460.8	784.2
Noncurrent Liabilities
Long-term debt		2,746.2	0
Long-term debt-affiliated		0	1,472.8
Deferred income taxes		1,348.1	1,255.7
Accrued liability for postretirement and postemployment benefits		49.4	53
Regulatory liabilities		321.6	295.7
Asset retirement obligations		25.7	23.2
Long-term debt		91.4	96.6
Total Noncurrent Liabilities		4,582.4	3,197
Total Liabilities		5,043.2	3,981.2
Equity
Common stock, $0.01 par value, 2,000,000,000 shares authorized; 399,841,350 and no shares outstanding, respectively		4	0
Additional paid-in capital		4,032.7	0
Retained earnings		46.9	0
Net Parent Investment		0	4,210.8
Accumulated other comprehensive loss	[1]	(27)	(34.5)
Total CPG Equity		4,056.6	4,176.3
Noncontrolling Interest		956.4	0
Total Equity		5,013	4,176.3
Total Liabilities and Equity		$ 10,056.2	$ 8,157.5
[1]	All amounts are net of tax. Amounts in parentheses indicate debits.

Statements of Consolidated and3

Statements of Consolidated and Combined Balance Sheets (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Statement of Financial Position [Abstract]
Accounts receivable less reserve	$ 0.6	$ 0.6
Common Stock, Par or Stated Value Per Share	$ 0.01
Common Stock, Shares Authorized	2,000,000,000
Common Stock, Shares, Outstanding	399,841,350	0

Statements Of Consolidated and4

Statements Of Consolidated and Combined Operations - USD ($) shares in Millions, $ in Millions		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014		Dec. 31, 2013
Net Revenues
Transportation revenues		$ 1,054.4	$ 990.8
Transportation revenues-affiliated		47.5	95.7
Storage revenues		171.4	144
Storage revenues-affiliated		26.2	53.2
Other revenues		35.4	64.3
Total Operating Revenues		1,334.9	1,348
Operating Expenses
Operation and maintenance		652.1	628.4
Operating and maintenance-affiliated		52.9	123.2
Depreciation and amortization		139.9	118.8
Gain on sale of assets and impairment, net		(52.9)	(34.5)
Property and other taxes		75.3	67.1
Total Operating Expenses		867.3	903
Equity Earnings in Unconsolidated Affiliates		60.5	46.6
Operating Income		528.1	491.6
Other Income (Deductions)
Interest expense		(67.6)	0	[1]
Interest expense-affiliated		(29.3)	(62)
Other, net		29.3	8.8
Total Other Deductions, net		(67.6)	(53.2)
Income from Continuing Operations before Income Taxes		460.5	438.4
Income Taxes		153	169.7
Income from Continuing Operations		307.5	268.7
(Loss) Income from Discontinued Operations-net of taxes		(0.4)	(0.6)
Net Income		307.1	268.1
Less: Net income attributable to noncontrolling interest		39.9
Net Income (Loss) Attributable to Parent		267.2	268.1
Income from Continuing Operations		$ 267.6	$ 268.7
Basic Earnings Per Share
Continuing Operations		$ 0.81	$ 0.84
Discontinued Operations		0	0
Basic Earnings Per Share		0.81	0.84
Diluted Earnings Per Share
Continuing Operations		0.81	0.84
Discontinued Operations		0	0
Diluted Earnings Per Share		$ 0.81	$ 0.84
Basic Average Common Shares Outstanding		328.5	317.6
Diluted Average Common Shares		329.1	317.6
Dividends Declared Per Common Share		$ 0.25	$ 0
Predecessor
Net Revenues
Transportation revenues					$ 850.9
Transportation revenues-affiliated					94.1
Storage revenues					142.8
Storage revenues-affiliated					53.6
Other revenues					39.1
Total Operating Revenues					1,180.5
Operating Expenses
Operation and maintenance					509
Operating and maintenance-affiliated					118.6
Depreciation and amortization					107
Gain on sale of assets and impairment, net					(18.6)
Property and other taxes					62.2
Total Operating Expenses					778.2
Equity Earnings in Unconsolidated Affiliates					35.9
Operating Income					438.2
Other Income (Deductions)
Interest expense	[1]				0
Interest expense-affiliated					(37.9)
Other, net					17.9
Total Other Deductions, net					(20)
Income from Continuing Operations before Income Taxes					418.2
Income Taxes					146.5
Income from Continuing Operations					271.7
(Loss) Income from Discontinued Operations-net of taxes					9
Net Income					280.7
Net Income (Loss) Attributable to Parent					280.7
Income from Continuing Operations					$ 271.7
Basic Earnings Per Share
Continuing Operations					$ 0.86
Discontinued Operations					0.03
Basic Earnings Per Share					0.89
Diluted Earnings Per Share
Continuing Operations					0.86
Discontinued Operations					0.03
Diluted Earnings Per Share					$ 0.89
Basic Average Common Shares Outstanding					317.6
Diluted Average Common Shares					317.6
Dividends Declared Per Common Share					$ 0
[1]	Refer to Note 4, "Transactions with Affiliates" for a discussion of interest expense-affiliated for the year ended December 31, 2014 and 2013.

Statements of Consolidated and5

Statements of Consolidated and Combined Comprehensive Income - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015		Dec. 31, 2014	Dec. 31, 2013
Net Income		$ 307.1		$ 268.1
Net unrealized gain on cash flow hedges	[1]	0.2		1
Unrecognized pension and OPEB benefit (costs)	[3]	5.2	[2]	(9.7)
Total other comprehensive income (loss)	[4]	5.4		(8.7)
Total Comprehensive Income		312.5		259.4
Less: Comprehensive Income-noncontrolling interest		40		0
Comprehensive Income-controlling interests		$ 272.5		$ 259.4
Predecessor
Net Income					$ 280.7
Net unrealized gain on cash flow hedges	[1]				1.1
Unrecognized pension and OPEB benefit (costs)	[3]				8.2
Total other comprehensive income (loss)	[4]				9.3
Total Comprehensive Income					290
Less: Comprehensive Income-noncontrolling interest					0
Comprehensive Income-controlling interests					$ 290
[1]	Net unrealized gain on derivatives qualifying as cash flow hedges, net of $0.2 million, $0.7 million and $0.6 million tax expense in 2015, 2014 and 2013, respectively.
[2]	Unrecognized pension and OPEB costs are primarily related to pension and OPEB remeasurement recorded during 2015.
[3]	Unrecognized pension and other postretirement ("OPEB") benefit (costs), net of $1.2 million tax benefit, $6.1 million tax benefit, and $5.3 million tax expense in 2015, 2014 and 2013, respectively.
[4]	All amounts are net of tax. Amounts in parentheses indicate debits.

Statements of Consolidated and6

Statements of Consolidated and Combined Comprehensive Income (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Tax	$ 0.2	$ 0.7
Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Tax	$ 1.2	$ 6.1
Predecessor
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Tax			$ 0.6
Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Tax			$ (5.3)

Statements Of Consolidated and7

Statements Of Consolidated and Combined Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Net Income	$ 307.1	$ 268.1
Adjustments to Reconcile Net Income to Net Cash from Continuing Operations:
Depreciation and amortization	139.9	118.8
Deferred income taxes and investment tax credits	131.9	142.6
Deferred revenue	4.2	1.6
Equity-based compensation expense and profit sharing contribution	9.4	6.3
Gain on sale of assets and impairment, net	(52.9)	(34.5)
Equity earnings in unconsolidated affiliates	(60.5)	(46.6)
Loss (income) from discontinued operations-net of taxes	0.4	0.6
Amortization of debt related costs	3.1	0
AFUDC equity	(28.3)	(11)
Distributions of earnings received from equity investees	57.2	37.8
Accounts receivable	(17.4)	(20.3)
Accounts receivable-affiliated	34.7	(3.6)
Accounts payable	(5)	2.8
Accounts payable-affiliated	(53.6)	12.4
Customer deposits	(22.9)	77.5
Taxes accrued	8.2	12
Interest accrued	9.4	0
Exchange gas receivable/payable	(0.3)	1.1
Other accruals	50.2	0.9
Prepayments and other current assets	(27.1)	(4.4)
Regulatory assets/liabilities	20.2	9
Postretirement and postemployment benefits	(4.4)	(1.3)
Deferred charges and other noncurrent assets	(16.3)	(4.3)
Other noncurrent liabilities	6.5	0.7
Net Operating Activities from Continuing Operations	493.7	566.2
Net Operating Activities (used for) from Discontinued Operations	0.2	1.4
Net Cash Provided by (Used in) Operating Activities	493.5	564.8
Investing Activities
Capital expenditures	(1,181)	(747.2)
Insurance recoveries	2.1	11.3
Changes in short-term lendings-affiliated	145.5	(57.2)
Proceeds from disposition of assets	77.6	9.3
Contributions to equity investees	(1.4)	(69.2)
Distributions from equity investees	16	0
Other investing activities	(27.4)	(7.1)
Net Cash Flows used for Investing Activities	(968.6)	(860.1)
Financing Activities
Change in short-term borrowings	15	0
Change in short-term borrowings-affiliated	(252.5)	(467.1)
Issuance of long-term debt	2,745.9	0
Debt related costs	(23.6)	(6.4)
Issuance of long-term debt-affiliated	1,217.3	768.9
Payments of long-term debt-affiliated, including current portion	(2,807.8)	0
Proceeds from issuance of common units, net of offering costs	1,168.4	0
Issuance of common stock, net of offering costs	1,394.7	0
Distribution of IPO proceeds to parent	(500)	0
Distribution to NiSource	(1,450)	0
Distribution to noncontrolling interest	(23.2)	0
Dividends paid - common stock	(79.5)	0
Transfer from parent	0.8	0
Net Cash Flows from Financing Activities	1,405.5	295.4
Change in cash and cash equivalents	930.4	0.1
Cash and cash equivalents at beginning of period	0.5	0.4
Cash and cash equivalents at beginning of period	930.9	0.5	$ 0.4
Predecessor
Net Income			280.7
Adjustments to Reconcile Net Income to Net Cash from Continuing Operations:
Depreciation and amortization			107
Deferred income taxes and investment tax credits			173.9
Deferred revenue			(7.8)
Equity-based compensation expense and profit sharing contribution			2.2
Gain on sale of assets and impairment, net			(18.6)
Equity earnings in unconsolidated affiliates			(35.9)
Loss (income) from discontinued operations-net of taxes			(9)
Amortization of debt related costs			0
AFUDC equity			(6.8)
Distributions of earnings received from equity investees			32.1
Accounts receivable			2.8
Accounts receivable-affiliated			(10.1)
Accounts payable			5.5
Accounts payable-affiliated			16.3
Customer deposits			1.3
Taxes accrued			(33.8)
Interest accrued			0
Exchange gas receivable/payable			(0.5)
Other accruals			0.8
Prepayments and other current assets			21.7
Regulatory assets/liabilities			42.6
Postretirement and postemployment benefits			(115.3)
Deferred charges and other noncurrent assets			9.9
Other noncurrent liabilities			(15.6)
Net Operating Activities from Continuing Operations			443.4
Net Operating Activities (used for) from Discontinued Operations			(13.8)
Net Cash Provided by (Used in) Operating Activities			457.2
Investing Activities
Capital expenditures			(674.8)
Insurance recoveries			6.4
Changes in short-term lendings-affiliated			(3.2)
Proceeds from disposition of assets			15.4
Contributions to equity investees			(125.5)
Distributions from equity investees			0
Other investing activities			(9.2)
Net Cash Flows used for Investing Activities			(790.9)
Financing Activities
Change in short-term borrowings			0
Change in short-term borrowings-affiliated			391
Issuance of long-term debt			0
Debt related costs			0
Issuance of long-term debt-affiliated			65.1
Payments of long-term debt-affiliated, including current portion			0
Proceeds from issuance of common units, net of offering costs			0
Issuance of common stock, net of offering costs			0
Distribution of IPO proceeds to parent			0
Distribution to NiSource			(123)
Distribution to noncontrolling interest			0
Dividends paid - common stock			0
Transfer from parent			0
Net Cash Flows from Financing Activities			333.1
Change in cash and cash equivalents			(0.6)
Cash and cash equivalents at beginning of period	$ 0.5	0.4	1
Cash and cash equivalents at beginning of period		$ 0.5	$ 0.4

Statements Of Consolidated and8

Statements Of Consolidated and Combined Equity - USD ($) shares in Millions, $ in Millions	Total		Common Stock	Additional Paid-in Capital	Retained Earnings	Parent	Accumulated Other Comprehensive Income Loss	Noncontrolling Interest
Beginning Balance (Predecessor) at Dec. 31, 2012	$ 3,743.3		$ 0	$ 0	$ 0	$ 3,778.4	$ (35.1)	$ 0
Net Income | Predecessor	280.7		0	0	0	280.7	0	0
Other Comprehensive Income, net of tax | Predecessor	9.3	[1]	0	0	0	0	9.3	0
Dividends | Predecessor	(123)		0	0	0	(123)	0	0
Net Transfers (To) From Parent | Predecessor	5.3		0	0	0	5.3	0	0
Distribution of IPO proceeds to parent | Predecessor	0
Distribution to NiSource | Predecessor	(123)
Ending Balance (Predecessor) at Dec. 31, 2013	3,915.6		0	0	0	3,941.4	(25.8)	0
Net Income	268.1		0	0	0	268.1	0	0
Other Comprehensive Income, net of tax	(8.7)	[1]	0	0	0	0	(8.7)	0
Net Transfers (To) From Parent	1.3		0	0	0	1.3	0	0
Distribution of IPO proceeds to parent	0
Distribution to NiSource	0
Ending Balance at Dec. 31, 2014	4,176.3		0	0	0	4,210.8	(34.5)	0
Net Income	307.1		0	0	126.4	140.8	0
Income (Loss) Attributable to Noncontrolling Interest	39.9
Other Comprehensive Income, net of tax	5.4	[1]	0	0	0	0	5.3	0.1
Net Transfers (To) From Parent	6.3		0	0	0	6.3	0	0
Allocation of AOCI to noncontrolling interest	0		0	0	0	0	2.2	(2.2)
Issuance of common units of CPPL	1,168.4		0	0	0	0	0
Distribution of IPO proceeds to parent	(500)		0	0	0	(500)	0	0
Distribution to NiSource	(1,450)		0	0	0	(1,450)	0	0
Purchase of additional interest in Columbia OpCo	0		0	0	0	227.1	0	(227.1)
Distribution to noncontrolling interest	(23.2)		0	0	0	0	0	(23.2)
Reclassification of net parent investment to additional paid-in capital	0		0	2,635	0	(2,635)	0	0
Issuance of common stock at Separation	0		3.2	(3.2)	0	0	0	0
Net transfers from NiSource subsequent to Separation	$ 1.5		$ 0	$ 1	$ 0	$ 0	$ 0	$ 0.5
Issuance of common stock, net of offering costs	1,394.7		0.8	1,393.9	0	0	0	0
Long-term incentive plan	$ 6		$ 0	$ 6	$ 0	$ 0	$ 0	$ 0
Common stock dividends	(79.5)		0	0	(79.5)	0	0	0
Ending Balance at Dec. 31, 2015	$ 5,013		$ 4	$ 4,032.7	$ 46.9	$ 0	$ (27)	$ 956.4
[1]	All amounts are net of tax. Amounts in parentheses indicate debits.

Statements Of Consolidated and9

Statements Of Consolidated and Combined Equity (Parenthetical) $ in Millions	12 Months Ended
	Dec. 31, 2015USD ($)
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%

Nature of Operations And Summar

Nature of Operations And Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2015
Nature of Operations And Summary of Significant Accounting Policies [Abstract]
Significant Accounting Policies	Nature of Operations and Summary of Significant Accounting Policies A. Company Structure and Basis of Presentation . Columbia Pipeline Group, Inc. ("CPG") is a growth-oriented Delaware corporation formed by NiSource Inc. ("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. All periods prior to September 26, 2014 reflect the combined financial position, results of operations and cash flows for CPG's Predecessor (the "Predecessor"). 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 did 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. CPG’s accompanying Consolidated and Combined Financial Statements have been prepared in accordance with GAAP. 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. Also included in the Consolidated and Combined Financial Statements are equity method investments Hardy Storage, Millennium Pipeline, and Pennant. All intercompany transactions and balances have been eliminated. B. Use of Estimates. The preparation of financial statements in conformity with accounting principles generally accepted in the United States requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. C. Cash and Cash Equivalents. Cash and cash equivalents are liquid marketable securities with an original maturity date of less than three months. D. Allowance for Uncollectible Accounts. The reserve for uncollectible receivables is CPG's best estimate of the amount of probable credit losses in the existing accounts receivable. Collectability of accounts receivable is reviewed regularly and an allowance is established or adjusted, as necessary, using the specific identification method. Account balances are charged against the allowance when it is anticipated the receivable will not be recovered. E. Basis of Accounting for Rate-Regulated Subsidiaries . Rate-regulated subsidiaries account for and report assets and liabilities consistent with the economic effect of the way in which regulators establish rates, if the rates established are designed to recover the costs of providing the regulated service and it is probable that such rates can be charged and collected. Certain expenses and credits subject to utility regulation or rate determination normally reflected in income are deferred on the Consolidated Balance Sheets and are recognized in income as the related amounts are included in service rates and recovered from or refunded to customers. In the event that regulation significantly changes the opportunity for CPG to recover its costs in the future, all or a portion of CPG’s regulated operations may no longer meet the criteria for regulatory accounting. In such an event, a write-down of all or a portion of CPG’s existing regulatory assets and liabilities could result. If CPG is unable to continue to apply the provisions of regulatory accounting, CPG would be required to apply the provisions of Discontinuation of Rate-Regulated Accounting. In management’s opinion, CPG’s regulated subsidiaries will be subject to regulatory accounting for the foreseeable future. Please see Note 11, "Regulatory Matters," in the Notes to Consolidated and Combined Financial Statements for further discussion. F. Property, Plant and Equipment and Related AFUDC and Maintenance . Property, plant and equipment is stated at cost. CPG's rate-regulated subsidiaries record depreciation using composite rates on a straight-line basis over the remaining service lives of the properties as approved by the appropriate regulators. CPG's non-regulated companies depreciate assets on a component basis on a straight-line basis over the remaining service lives of the properties. CPG capitalizes AFUDC on all classes of property except organization costs, land, autos, office equipment, tools and other general property purchases. The allowance is applied to construction costs for that period of time between the date of the expenditure and the date on which such project is placed in service. A combination of short-term borrowings, long-term debt and equity were used to fund construction efforts for all three years presented. The pre-tax rate for AFUDC debt and ADUFC equity are summarized in the table below: 2015 2014 2013 Debt Equity Debt Equity Debt Equity Predecessor Columbia Gas Transmission 1.8 % 6.3 % 0.9 % 3.0 % 2.5 % 3.2 % Columbia Gulf 2.9 % 6.3 % 2.1 % 9.4 % 2.5 % 3.2 % CPG follows the practice of charging maintenance and repairs, including the cost of removal of minor items of property, to expense as incurred. When regulated property that represents a retired unit is replaced or removed, the cost of such property is credited to utility plant, and such cost, net of salvage, is charged to the accumulated provision for depreciation in accordance with composite depreciation. G. Gas Stored-Base Gas. Base gas, which is valued at original cost, represents storage volumes that are maintained to ensure that adequate well pressure exists to deliver current gas inventory. There were no purchases of base gas during the years ended December 31, 2015 , 2014 and 2013 . Please see Note 7, "Gain on Sale of Assets," in the Notes to Consolidated and Combined Financial Statements for information regarding the sale of storage base gas in 2013 . Gas stored-base gas is included in Property, plant and equipment on the Consolidated Balance Sheets. H. Amortization of Software Costs. External and internal costs associated with computer software developed for internal use are capitalized. Capitalization of such costs commences upon the completion of the preliminary stage of each project. Once the installed software is ready for its intended use, such capitalized costs are amortized on a straight-line basis generally over a period of five years. CPG amortized $8.7 million in 2015 , $4.3 million in 2014 and $5.0 million in 2013 related to software costs. CPG’s unamortized software balance was $59.8 million and $18.3 million at December 31, 2015 and 2014 , respectively. I. Goodwill. CPG has $1,975.5 million in goodwill. All goodwill relates to the excess of cost over the fair value of the net assets acquired in the CEG acquisition on November 1, 2000. Please see Note 9, "Goodwill," in the Notes to Consolidated and Combined Financial Statements for further discussion. J. Impairments. An impairment loss on long-lived assets shall be recognized only if the carrying amount of a long-lived assets is not recoverable and exceeds its fair value. The test for impairment compares the carrying amount of the long-lived asset to the sum of the undiscounted cash flows expected to result from the use and eventual disposition of the asset. CPG recognized an impairment loss of $2.4 million for the year ended December 31, 2015 and zero for the years ended December 31, 2014 and 2013 . K. Revenue Recognition. Revenue is recorded as services are performed. Revenues are billed to customers monthly at rates established through the FERC's cost-based rate-making process or at rates less than those allowed by the FERC. Revenues are recorded on the accrual basis and include estimates for transportation provided but not billed. The demand and commodity charges for transportation of gas under long-term agreements are recognized separately. Demand revenues are recognized monthly over the term of the agreement with the customer regardless of the volume of natural gas transported. Commodity revenues for both firm and interruptible transportation are recognized in the period the transportation services are provided based on volumes of natural gas physically delivered at the agreed upon delivery point. CPG provides shorter term transportation and storage services for which cash is received at inception of the service period resulting in the recording of deferred revenues that are recognized in revenues over the period the services are provided. Storage capacity revenues are recognized monthly over the term of the agreement with the customer regardless of the volume of storage service actually utilized. Injection and withdrawal revenues are recognized in the period when volumes of natural gas are physically injected into or withdrawn from storage. CPG includes the subsidiary CEVCO, which owns the mineral rights to approximately 460,000 acres in the Marcellus and Utica shale areas. CEVCO leases or contributes the mineral rights to producers in return for royalty interest. Royalties from mineral interests are recognized on an accrual basis when earned and realized. Royalty revenue was $26.5 million , $43.8 million and $21.2 million for the years ended December 31, 2015 , 2014 and 2013 , respectively, and is included in "Other revenues" on the Statements of Consolidated and Combined Operations. CPG periodically recognizes gains on the conveyance of mineral interest related to pooling of assets (production rights) in joint undertakings intended to find, develop, or produce oil or gas from a particular property or group of properties. The gains are initially deferred if CPG has a substantial obligation for future performance. As the obligation for future performance is satisfied, the deferred revenue is relieved and the associated gain is recognized. Gains on conveyances amounted to $52.3 million , $34.5 million and $7.3 million for the years ended December 31, 2015 , 2014 and 2013 , respectively, and are included in "Gain on sale of assets and impairment, net" on the Statements of Consolidated and Combined Operations. L. 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: Year Ended December 31, (in millions) 2015 2014 2013 Predecessor Basic average common shares outstanding 328.5 317.6 317.6 Dilutive potential common shares: Shares restricted under stock plans 0.6 — — Diluted weighted average shares outstanding 329.1 317.6 317.6 Dividends. CPG paid a dividend of $0.125 per share to common stockholders on August 20, 2015 . On August 4, 2015 , CPG declared a dividend of $0.125 per share to common stockholders of record at October 30, 2015 , payable November 20, 2015 . On January 29, 2016 , CPG declared a dividend of $0.12875 per share to common stockholders of record at February 8, 2016 , payable February 19, 2016 . M. Estimated Rate Refunds . CPG collects revenue subject to refund pending final determination in rate proceedings. In connection with such revenues, estimated rate refund liabilities are recorded which reflect management’s current judgment of the ultimate outcomes of the proceedings. No provisions are made when, in the opinion of management, the facts and circumstances preclude a reasonable estimate of the outcome. N. Accounting for Exchange and Balancing Arrangements of Natural Gas. CPG enters into balancing and exchange arrangements of natural gas as part of its operations. CPG records a receivable or payable for its respective cumulative gas imbalances. These receivables and payables are recorded as “Exchange gas receivable” or “Exchange gas payable” on CPG’s Consolidated Balance Sheets, as appropriate. O. Income Taxes and Investment Tax Credits. CPG records income taxes to recognize full inter period tax allocations. Under the liability method, deferred income taxes are provided for the tax consequences of temporary differences by applying enacted statutory tax rates applicable to future years to differences between the financial statement carrying amounts and the tax basis of existing assets and liabilities. To the extent certain deferred income taxes of CPG are recoverable or payable through future rates, regulatory assets and liabilities have been established. In prior years, and for the period ending July 1, 2015, CPG joined in the filing of consolidated federal and state income tax returns with NiSource. CPG was a party to an agreement (“Tax Allocation Agreement”) that provides for the allocation of consolidated tax liabilities. The Tax Allocation Agreement generally provides that each party is allocated an amount of tax similar to that which would be owed had the party been separately subject to tax. In addition, the Tax Allocation Agreement provides that tax benefits associated with NiSource parent’s tax losses, excluding tax benefits from interest expense on acquisition debt, are allocated to and reduce the income tax liability of all NiSource subsidiaries having a positive separate company tax liability in a particular tax year. The amounts of such tax benefits allocated to CPG that were recorded in equity in 2015 , 2014 and 2013 were $5.8 million , $1.3 million and $5.3 million , respectively. P. Environmental Expenditures. CPG accrues for costs associated with environmental remediation obligations when the incurrence of such costs is probable and the amounts can be reasonably estimated, regardless of when the expenditures are actually made. The undiscounted estimated future expenditures are based on currently enacted laws and regulations, existing technology and estimated site-specific costs where assumptions may be made about the nature and extent of site contamination, the extent of cleanup efforts, costs of alternative cleanup methods and other variables. The liability is adjusted as further information is discovered or circumstances change. The reserves for estimated environmental expenditures are recorded on the Consolidated Balance Sheets in “Other Accruals” for short-term portions of these liabilities and “Other noncurrent liabilities” for the respective long-term portions of these liabilities. CPG establishes regulatory assets on the Consolidated Balance Sheets to the extent that future recovery of environmental remediation costs is probable through the regulatory process. Please see Note 19, "Other Commitments and Contingencies" in the Notes to Consolidated and Combined Financial Statements for further discussion. Q. Accounting for Investments. CPG accounts for its ownership interests in Millennium Pipeline using the equity method of accounting. Columbia Gas Transmission owns a 47.5% interest in Millennium Pipeline. The equity method of accounting is applied for investments in unconsolidated companies where CPG (or a subsidiary) owns 20 to 50 percent of the voting rights and can exercise significant influence. CPG owns a 50.0% interest in Hardy Storage for the periods presented. CPG reflects the investment in Hardy Storage as an equity method investment. Columbia Midstream entered into a 50:50 joint venture in 2012 with Hilcorp to construct Pennant, a new wet natural gas gathering infrastructure and NGL processing facilities to support natural gas production in the Utica Shale region of northeastern Ohio and western Pennsylvania. During the third quarter of 2015, an additional member, an affiliate of Williams Partners, joined the Pennant joint venture. Williams Partners' initial ownership investment in Pennant is 5.00% , and by funding specified investment amounts for future growth projects, Williams Partners can invest directly in the growth of Pennant. Such funding will potentially increase Williams Partners' ownership in Pennant up to 33.33% over a defined investment period. As a result of the buy-in, Columbia Midstream received $12.7 million in cash and recorded a gain of $2.9 million , and its ownership interest in Pennant decreased from 50.0% to 47.5% . CPG accounts for the joint venture under the equity method of accounting. R. Natural Gas and Oil Properties. CEVCO participates as a working interest partner in the development of a broader acreage dedication. The working interest allows CEVCO to invest in the drilling operations of the partnership in addition to a royalty interest in well production. Please see Note 1K, “Revenue Recognition,” in the Notes to Consolidated and Combined Financial Statements for further discussion regarding the royalty revenue. CEVCO uses the successful efforts method of accounting for natural gas and oil producing activities for their portion of drilling activities. Capitalized well costs are depleted based on the units of production method. CEVCO’s portion of unproved property investment is periodically evaluated for impairment. The majority of these costs generally relate to CEVCO’s portion of the working interest. The costs are capitalized and evaluated (at least quarterly) as to recoverability, based on changes brought about by economic factors and potential shifts in business strategy employed by management. Impairment of individually significant unproved property is assessed on a field-by-field basis considering a combination of time, geologic and engineering factors. The following table reflects the changes in capitalized exploratory well costs for the years ended December 31, 2015 and 2014 : (in millions) 2015 2014 Beginning Balance $ 14.9 $ 1.9 Additions pending the determination of proved reserves 1.3 20.1 Reclassifications of proved properties (14.5 ) (7.1 ) Ending Balance $ 1.7 $ 14.9 As of December 31, 2015 , there was $0.3 million of capitalized exploratory well costs that have been capitalized for more than one year relating to one project initiated in 2013 .

CPPL Initial Public Offering

CPPL Initial Public Offering	12 Months Ended
	Dec. 31, 2015
Initial Public Offering [Abstract]
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 the IPO. CPG owns the general partner of CPPL, 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 into CPG's results. As of December 31, 2015 , the portion of CPPL owned by the public is reflected as a noncontrolling interest in the Consolidated and Combined Financial Statements. The table below summarizes the effects of the changes in CPG's ownership interest in Columbia OpCo on equity: Year Ended (in millions) 2015 Net income attributable to CPG $ 267.2 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 $ 494.3

Recent Accounting Pronouncement

Recent Accounting Pronouncements	12 Months Ended
	Dec. 31, 2015
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
Recent Accounting Pronouncements	Recent Accounting Pronouncements In November 2015, the FASB issued ASU 2015-17, Income Taxes (Topic 740): Balance Sheet Classification of Deferred Taxes. ASU 2015-17 simplifies the presentation of deferred taxes by requiring that all deferred tax assets and liabilities be classified as noncurrent on the balance sheet. CPG is required to adopt ASU 2015-17 for periods beginning after December 15, 2016, including interim periods, and the new standard is to be applied prospectively or retrospectively to all presented periods with early adoption permitted. On December 31, 2015 CPG prospectively adopted ASU 2015-17 in the Consolidated and Combined Financial Statements and Notes to Consolidated and Combined Financial Statements. 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 is required to adopt ASU 2015-03 and ASU 2015-15 for periods beginning after December 15, 2015, including interim periods, and the guidance is to be applied retrospectively with early adoption permitted. The adoption of ASU 2015-3 and ASU 2015-15 will result in a reclassification from "Deferred charges and other" to "Long-term debt" of the unamortized balance of debt issuance costs. At December 31, 2015, the balance of unamortized debt issuance costs recorded in "Deferred charges and other" was $20.6 million . 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. CPG is currently evaluating the impact the adoption of ASU 2014-09 and ASU 2015-14 will have on the Consolidated and Combined Financial Statements and Notes to Consolidated and Combined Financial Statements. 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 is required to adopt ASU 2015-02 for periods beginning after December 15, 2015, including interim periods, and the guidance is to be applied retrospectively or using a modified retrospective approach, with early adoption permitted. CPG is currently evaluating the impact the adoption of ASU 2015-02 will have on the Consolidated and Combined Financial Statements and Notes to Consolidated and Combined Financial Statements but does not anticipate that the impact will be material.

Transactions with Affiliates

Transactions with Affiliates	12 Months Ended
	Dec. 31, 2015
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 subsidiaries of NiSource are no longer affiliates. Transactions with affiliates prior to the Separation are summarized below: Statement of Operations Year Ended (in millions) 2015 2014 2013 Predecessor Transportation revenues $ 47.5 $ 95.7 $ 94.1 Storage revenues 26.2 53.2 53.6 Other revenues 0.2 0.3 0.3 Operation and maintenance expense 52.9 123.2 118.6 Interest expense 29.3 62.0 37.9 Interest income 2.5 0.7 0.7 Balance Sheet (in millions) December 31, 2015 December 31, 2014 Accounts receivable $ — $ 180.0 Current portion of long term debt- affiliated — 115.9 Short-term borrowings — 252.5 Accounts payable — 53.6 Long-term debt — 1,472.8 Transportation, Storage and Other Revenues . CPG provided natural gas transportation, storage and other services to subsidiaries of NiSource, which were deemed to be affiliates prior to the Separation. 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. CPG was charged interest for long-term debt of $31.0 million , $61.6 million and $40.6 million for the years ended December 31, 2015 , 2014 and 2013 , respectively, offset by associated AFUDC of $2.4 million , $2.7 million and $6.8 million for the years ended December 31, 2015 , 2014 and 2013 , respectively. 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 was 1.21% at June 30, 2015 and 0.70% at December 31, 2014 , respectively. The interest expense for short-term borrowings charged for the years ended December 31, 2015 , 2014 and 2013 was $0.7 million , $3.1 million and $4.1 million , respectively. Accounts Receivable . CPG included in accounts receivable amounts due from the money pool discussed above of $145.5 million at December 31, 2014 for subsidiaries in a net deposit position. Also included in the balance at December 31, 2014 are amounts due from subsidiaries of NiSource for transportation and storage services of $34.5 million . Net cash flows related to the money pool receivables, including the receipt of money pool deposits from NiSource at the time of Separation, are included as Investing Activities on the Statements of Consolidated and Combined Statements of Cash Flows. All other affiliated receivables are included as Operating Activities. Short-term Borrowings . The subsidiaries of CPG entered into an intercompany money pool agreement with NiSource Finance with $750.0 million of reserved borrowing capacity. Following the Separation, the agreement is with CPG. In furtherance of the money pool agreement, CPG entered into a $1,500.0 million revolving credit agreement on December 5, 2014. The CPG revolving credit agreement became effective at the completion of the Separation with a termination date of July 2, 2020. Each of CEG, OpCo GP and Columbia OpCo is a guarantor of CPG's revolving credit facility. As guarantors and restricted subsidiaries, CEG, OpCo GP and Columbia OpCo are subject to various customary covenants and restrictive provisions which, among other things, limit CPG’s and its restricted subsidiaries’ ability to incur additional indebtedness, guarantees and/or liens; consolidate, merge or transfer all or substantially all of their assets; make certain investments or restricted payments; modify certain material agreements; engage in certain types of transactions with affiliates; dispose of assets; and prepay certain indebtedness; each of which is subject to customary and usual exceptions and baskets, including an exception to the limitation on restricted payments for distributions of available cash, as permitted by their organizational documents. The restricted payment provision does not prohibit CPG 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 not 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 December 31, 2015 , 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. CPG’s revolving credit facility also contains customary events of default, including cross default provisions that apply to any other indebtedness CPG may have with an outstanding principal amount in excess of $50.0 million . If a default occurred, the relevant lenders could elect to declare the debt, together with accrued interest and other fees, to be immediately due and payable and proceed against Columbia OpCo as a guarantor. The balance of Short-term Borrowings at December 31, 2014 of $252.5 million included those subsidiaries of CPG in a net borrower position of the NiSource Finance money pool discussed above. Net cash flows related to Short-term Borrowings, including the repayment of money pool borrowings to NiSource at the time of Separation, are included as Financing Activities on the Statements of Consolidated and Combined Statements of Cash Flows. Accounts Payable . The affiliated accounts payable balance primarily included amounts due for services received from NiSource Corporate Services and interest payable to NiSource Finance. Long-term Debt . CPG's long-term financing requirements, prior to the private placement of seniors notes on May 22, 2015, were satisfied through borrowings from NiSource Finance. CPG used a portion of net proceeds from the senior notes to repay approximately $1,087.3 million of intercompany debt and short-term borrowings, net of amounts due from the money pool, between CPG and NiSource Finance. Details of the affiliated long-term debt balance are summarized in the table below: Origination Date Interest Rate Maturity Date December 31, 2015 December 31, 2014 (in millions) November 28, 2005 (1) 5.41 % November 30, 2015 $ — $ 115.9 November 28, 2005 5.45 % November 28, 2016 — 45.3 November 28, 2005 5.92 % November 28, 2025 — 133.5 November 28, 2012 4.63 % November 28, 2032 — 45.0 November 28, 2012 4.94 % November 30, 2037 — 95.0 December 19, 2012 5.16 % December 21, 2037 — 55.0 November 28, 2012 5.26 % November 28, 2042 — 170.0 December 19, 2012 5.49 % December 18, 2042 — 95.0 December 9, 2013 4.75 % December 31, 2016 — 834.0 Total Long-term Debt $ — $ 1,588.7 (1) The debt balance for the note originating on November 28, 2005 and maturing on November 30, 2015 is included in "Current portion of long-term debt-affiliated" on the Consolidated Balance Sheets as of December 31, 2014. Dividends . Prior to the Separation, 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 and $1,450.0 million of proceeds related to the issuance of senior notes in May 2015. CPG paid no dividends to NiSource in the year ended December 31, 2014 and paid $123.0 million to NiSource in the year ended December 31, 2013 . There were no restrictions on the payment by CPG of dividends to NiSource.

Short-Term Borrowings

Short-Term Borrowings	12 Months Ended
	Dec. 31, 2015
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 London Interbank Offered Rate ("LIBOR"), plus 1.000 percent , each of which is subject to a margin that varies from 0.000 percent to 0.650 percent per annum, according to the credit rating of CPG, or (ii) the Eurodollar rate plus a margin that varies from 1.000 percent to 1.650 percent per annum, according to the credit rating of CPG. 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 December 31, 2015 , 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) 5.75 to 1.00 for any period of four consecutive fiscal quarters (each, a “test period”) ending December 31, 2015, (ii) 5.50 to 1.00 for any test period ending after December 31, 2015 and on or before December 31, 2017, and (iii) 5.00 to 1.00 for any test period ending after December 31, 2017, provided that after December 31, 2017, and during a Specified Acquisition Period (as defined in the 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. As of December 31, 2015 , CPG had no borrowings outstanding and had $18.1 million in letters of credit under the revolving credit facility. 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 to Columbia OpCo. 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 distribution of $0.1675 on each common and subordinated unit. However, the determination to make any distributions of cash is subject to the discretion of the general partner. At December 31, 2015 , 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) 5.75 to 1.00 for the period of four consecutive fiscal quarters (“test period”) ending December 31, 2015, (ii) 5.50 to 1.00 for any test period ending after December 31, 2015 and on or before December 31, 2017, and (iii) 5.00 to 1.00 for any test period ending after December 31, 2017, provided that after December 31, 2017 and during a Specified Acquisition Period (as defined in the 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. As of 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 December 31, 2015 , CPG had no Promissory Notes outstanding under the Program. Short-term borrowings were as follows: At December 31, (in millions) 2015 2014 Commercial paper borrowings $ — $ — CPG credit facility borrowings — — CPPL credit facility borrowings, weighted average interest rate of 1.28% at December 31, 2015 15.0 — Total Short-Term Borrowings $ 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 Statements of Consolidated and Combined Cash Flows.

Long-Term Debt

Long-Term Debt	12 Months Ended
	Dec. 31, 2015
Long-term Debt, Current and Noncurrent [Abstract]
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 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. Under certain circumstances set forth in the Registration Rights Agreement, in lieu of a registered exchange offer, CPG and the Guarantors must file, and use reasonable best efforts to cause to become effective, a shelf registration statement for the resale of the Notes. If CPG fails to satisfy these obligations on a timely basis, the annual interest borne by the Notes will be increased by up to 0.50% per annum until the exchange offer is completed or the shelf registration statement is declared effective. The following table summarizes the outstanding long-term debt maturities at December 31, 2015 . Year Ending December 31, (in millions) 2016 $ — 2017 — 2018 500.0 2019 — 2020 750.0 After 1,500.0 Total (1) $ 2,750.0 (1) This amount excludes unamortized discount of $3.8 million . The unamortized discount applicable to the Notes is being amortized over the weighted average life of the Notes.

Gain on Sale of Assets

Gain on Sale of Assets	12 Months Ended
	Dec. 31, 2015
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 years ended December 31, 2015 , 2014 and 2013 , gains on conveyances amounted to $52.3 million , $34.5 million and $7.3 million , respectively, and are included in "Gain on sale of assets and impairment, net" on the Statements of Consolidated and Combined Operations. Included in the gains on conveyances is a cash bonus payment of $35.8 million received by CEVCO from CNX Gas Company LLC during the year ended December 31, 2015 , for the lease of Utica Shale and Upper Devonian gas rights in Greene and Washington Counties in Pennsylvania and Marshall and Ohio Counties in West Virginia. As of December 31, 2015 and 2014 , deferred gains of approximately $8.1 million and $19.6 million , respectively, were deferred pending performance of future obligations and recorded in "Deferred revenue" on the Consolidated Balance Sheets. In 2013, Columbia Gas Transmission sold storage base gas. The difference between the sale proceeds and amounts capitalized to Property, plant and equipment resulted in a gain of $11.1 million .

Property, Plant And Equipment

Property, Plant And Equipment	12 Months Ended
	Dec. 31, 2015
Property, Plant and Equipment [Abstract]
Property, Plant And Equipment	Property, Plant and Equipment CPG’s property, plant and equipment on the Consolidated Balance Sheets are classified as follows: At December 31, (in millions) 2015 2014 Property, plant and equipment Pipeline and other transmission assets $ 6,160.4 $ 5,333.0 Storage facilities 1,370.1 1,326.5 Gas stored base gas 299.5 299.5 Gathering and processing facilities 370.2 263.3 Construction work in process 487.6 454.2 General plant, software, and other assets 364.5 258.9 Property, plant and equipment 9,052.3 7,935.4 Accumulated depreciation and amortization (2,988.6 ) (2,976.8 ) Net property, plant and equipment $ 6,063.7 $ 4,958.6 The table below lists CPG's applicable annual depreciation rates: Year Ended December 31, 2015 2014 2013 Predecessor Depreciation rates Pipeline and other transmission assets 1.00% - 2.50% 1.00% - 2.50% 1.00% - 2.50% Storage facilities 2.19% - 3.00% 2.19% - 3.30% 2.19% - 3.50% Gathering and processing facilities 1.67% - 2.50% 1.67% - 2.50% 1.67% - 2.50% General plant, software, and other assets 1.00% - 21.00% 1.00% - 10.00% 1.00% - 10.00%

Goodwill

Goodwill	12 Months Ended
	Dec. 31, 2015
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 December 31, 2015 and December 31, 2014 were $1,975.5 million . The 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. In estimating the fair value of Columbia Gas Transmission Operations for the May 1, 2012 test, the Predecessor used a weighted average of the income and market approaches. The income approach utilized a discounted cash flow model. This model was based on management’s short-term and long-term forecast of operating performance for each reporting unit. The two main assumptions used in the models were the growth rates, which were based on the cash flows from operations for the reporting unit, and the weighted average cost of capital, or discount rate. The starting point for the reporting unit’s cash flow from operations was the detailed five year plan, which takes into consideration a variety of factors such as the current economic environment, industry trends, and specific operating goals set by management. The discount rates were based on trends in overall market as well as industry specific variables and include components such as the risk-free rate, cost of debt, and company volatility at May 1, 2012. Under the market approach, the Predecessor utilized three market-based models to estimate the fair value of the reporting unit: (i) the comparable company multiples method, which estimated fair value of the reporting unit by analyzing EBITDA multiples of a peer group of publicly traded companies and applying that multiple to the reporting unit’s EBITDA, (ii) the comparable transactions method, which valued the reporting unit based on observed EBITDA multiples from completed transactions of peer companies and applying that multiple to the reporting unit’s EBITDA, and (iii) the market capitalization method, which used the NiSource share price and allocated NiSource’s total market capitalization among both the goodwill and non-goodwill reporting units based on the relative EBITDA, revenues, and operating income of each reporting unit. Each of the three market approaches were calculated with the assistance of a third-party valuation firm, using multiples and assumptions inherent in today’s market. The degree of judgment involved and reliability of inputs into each model were considered in weighting the various approaches. The resulting estimate of fair value of the reporting unit, using the weighted average of the income and market approaches, exceeded its carrying value, indicating that no impairment exists under step 1 of the annual impairment test. Certain key assumptions used in determining the fair value of the reporting unit included planned operating results, discount rates and the long-term outlook for growth. In 2012, the Predecessor used the discount rate of 5.60% for Columbia Gas Transmission Operations, resulting in excess fair value of approximately $1,643.0 million . GAAP allows entities testing goodwill for impairment the option of performing a qualitative ("step 0") assessment before calculating the fair value of a reporting unit for the goodwill impairment test. If a step 0 assessment is performed, an entity is no longer required to calculate the fair value of a reporting unit unless the entity determines that, based on that assessment, it is more likely than not that its fair value is less than its carrying amount. The Predecessor applied the qualitative step 0 analysis to the reporting unit for the annual impairment test performed as of May 1, 2015. For the current year test, the Predecessor 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 the 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. CPG reviewed the market capitalization method due to the recent decline in CPG's share price. Following this review CPG determined there were no indicators that would require goodwill impairment testing subsequent to May 1, 2015.

Asset Retirement Obligations

Asset Retirement Obligations	12 Months Ended
	Dec. 31, 2015
Asset Retirement Obligation [Abstract]
Asset Retirement Obligations	Asset Retirement Obligations Changes in CPG’s liability for asset retirement obligations for the years 2015 and 2014 are presented in the table below: (in millions) 2015 2014 Beginning Balance $ 23.2 $ 26.3 Accretion expense 1.2 1.5 Additions 4.1 2.2 Settlements — (6.6 ) Change in estimated cash flows (2.8 ) (0.2 ) Ending Balance $ 25.7 $ 23.2 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	12 Months Ended
	Dec. 31, 2015
Regulatory Assets and Liabilities Disclosure [Abstract]
Regulatory Matters	Regulatory Matters Regulatory Assets and Liabilities Current and noncurrent regulatory assets and liabilities were comprised of the following items: At December 31, (in millions) 2015 2014 Assets Unrecognized pension benefit and other postretirement benefit costs $ 135.2 $ 120.9 Other postretirement costs 9.0 10.8 Deferred taxes on AFUDC equity 35.4 21.8 Other 3.1 4.5 Total Regulatory Assets $ 182.7 $ 158.0 At December 31, (in millions) 2015 2014 Liabilities Cost of removal $ 154.7 $ 157.6 Regulatory effects of accounting for income taxes 10.6 10.9 Unrecognized pension benefit and other postretirement benefit costs 0.7 8.3 Other postretirement costs 155.6 117.3 Other 1.2 2.9 Total Regulatory Liabilities $ 322.8 $ 297.0 No regulatory assets are earning a return on investment at December 31, 2015 . Regulatory assets of $35.6 million are covered by specific regulatory orders and are being recovered as components of cost of service over a remaining life of up to 7 years. Assets: Unrecognized pension benefit and other postretirement benefit costs – In 2007, the Predecessor adopted certain updates of ASC 715 which required, among other things, the recognition in other comprehensive income or loss of the actuarial gains or losses and the prior service costs or credits that arise during the period but that are not immediately recognized as components of net periodic benefit costs. Certain subsidiaries defer the costs as a regulatory asset in accordance with regulatory orders to be recovered through base rates. Other postretirement costs – Primarily comprised of costs approved through rate orders to be collected through future base rates, revenue riders or tracking mechanisms. Deferred taxes on AFUDC equity - ASC 740 considers the equity component of AFUDC a temporary difference for which deferred income taxes must be provided. CPG is required to record the deferred tax liability for the equity component of AFUDC offset to this regulatory asset for wholly-owned subsidiaries and equity method investments. The regulatory asset is itself a temporary difference for which deferred incomes taxes are recognized. Liabilities: Cost of removal - Represents anticipated costs of removal that have been, and continue to be, included in depreciation rates and collected in the service rates of some rate-regulated subsidiaries for future costs to be incurred. Regulatory effects of accounting for income taxes - Represents amounts related to state income taxes collected at a higher rate than the current statutory rates assumed in rates, which is being amortized to earnings in association with depreciation on related property. Unrecognized pension benefit and other postretirement benefit costs - In 2007, the Predecessor adopted certain updates of ASC 715 which required, among other things, the recognition in other comprehensive income or loss of the actuarial gains or losses and the prior service costs or credits that arise during the period but that are not immediately recognized as components of net periodic benefit costs. Certain subsidiaries defer the benefits as a regulatory liability in accordance with regulatory orders. Other postretirement costs - Primarily represents amounts being collected through rates in excess of the GAAP expense on a cumulative basis. In addition, according to regulatory order, a certain level of benefit expense is recognized in the Predecessor’s results, which exceeds the amount funded in the plan. Regulatory Matters Columbia Gas Transmission Customer Settlement. On January 24, 2013, the FERC approved the Settlement. In March 2013, Columbia Gas Transmission paid $88.1 million in refunds to customers pursuant to the Settlement with its customers in conjunction with its comprehensive interstate natural gas pipeline modernization program. The refunds were made as part of the Settlement, which included a $50.0 million refund to max rate contract customers and a base rate reduction retroactive to January 1, 2012. Columbia Gas Transmission expects to invest approximately $1.5 billion over a five-year period, which began in 2013, to modernize its system to improve system integrity and enhance service reliability and flexibility. The Settlement with firm customers includes an initial five-year term with provisions for potential extensions thereafter. The Settlement also provided for a depreciation rate reduction to 1.5% and elimination of negative salvage rate effective January 1, 2012 and for a second base rate reduction, which began January 1, 2014, which equates to approximately $25.0 million in revenues annually thereafter. The Settlement includes a CCRM, a tracker mechanism that will allow Columbia Gas Transmission to recover, through an additive capital demand rate, its revenue requirement for capital investments made under Columbia Gas Transmission's long-term plan to modernize its interstate transmission system. The CCRM provides for a 14.0% revenue requirement with a portion designated as a recovery of taxes other than income taxes. The additive demand rate is earned on costs associated with projects placed into service by October 31 each year. The initial additive demand rate was effective on February 1, 2014. The CCRM will give Columbia Gas Transmission the opportunity to recover its revenue requirement associated with a $1.5 billion investment in the modernization program. The CCRM recovers the revenue requirement associated with qualifying modernization costs that Columbia Gas Transmission incurs after satisfying the requirement associated with $100.0 million in annual maintenance capital expenditures. The CCRM applies to Columbia Gas Transmission's transportation shippers. The CCRM will not exceed $300.0 million per year in investment in eligible facilities, subject to a 15.0% annual tolerance and a total cap of $1.5 billion for the entire five-year initial term. On January 28, 2016, Columbia Gas Transmission received FERC approval of its December 2015 filing to recover costs associated with the third year of its comprehensive system modernization program. Total program adjusted spend to date is $937.1 million . The program includes replacement of bare steel and wrought iron pipeline and compressor facilities, enhancements to system inspection capabilities and improvements in control systems. In December 2015, Columbia Gas Transmission filed an extension of this settlement and has requested FERC’s approval of the customer agreement by March 31, 2016. 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 intends to file a cost and revenue study with 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. Under section 4 of the NGA, the FERC allows for the recovery of certain operating costs of our interstate transmission and storage companies that are significant and recurring in nature 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 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. A significant portion of our revenues and expenses are related to the recovery of costs under these tracking mechanisms. The associated costs for which we are obligated are reported in operating expenses with the offsetting recoveries reflected in revenues. These costs include: third-party transportation, electric compression, and certain approved operational purchases of natural gas. The tracking of certain environmental costs ended in 2015. Additionally, we recover fuel for company used gas and lost and unaccounted for gas through in-kind trackers where a retainage rate is charged to each customer to collect fuel. The recoveries and costs are both reflected in operating expenses.

Equity Method Investments

Equity Method Investments	12 Months Ended
	Dec. 31, 2015
Variable Interest Entities And Equity Investments [Abstract]
Variable Interest Entities And 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 Consolidated Balance Sheets and CPG's portion of the results is reflected in "Equity Earnings in Unconsolidated Affiliates" on CPG's Statements of Consolidated and Combined Operations. In the normal course of business, CPG engages in various transactions with these unconsolidated affiliates. During the year ended December 31, 2015 , CPG had billed approximately $13.1 million for services and other costs to Millennium Pipeline. These investments are integral to CPG's business. Contributions are made to these equity investees to fund CPG's share of projects. The following is a list of CPG's equity method investments at December 31, 2015 : Investee Type of Investment % of Voting Power or Interest Held Hardy Storage Company, LLC LLC Membership 50.0 % Pennant Midstream, LLC LLC Membership 47.5 % Millennium Pipeline Company, L.L.C. LLC Membership 47.5 % As the Millennium Pipeline, Hardy Storage and Pennant investments are considered, in aggregate, material to CPG's business, the following table contains condensed summary financial data. Year Ended December 31, (in millions) 2015 2014 2013 Predecessor Millennium Pipeline Statement of Income Data: Net Revenues $ 206.3 $ 190.5 $ 157.8 Operating Income 136.1 128.8 101.3 Net Income 98.0 89.6 63.0 Balance Sheet Data: Current Assets 35.7 32.1 38.3 Noncurrent Assets 987.1 1,016.3 1,033.8 Current Liabilities 44.4 42.6 58.8 Noncurrent Liabilities 535.8 568.3 599.7 Total Members’ Equity 442.6 437.5 413.6 Contribution/Distribution Data: (1) Contributions to Millennium Pipeline 1.4 2.6 16.6 Distribution of earnings from Millennium Pipeline 47.5 35.6 29.0 Hardy Storage Statement of Income Data: Net Revenues $ 23.4 $ 23.6 $ 24.4 Operating Income 15.3 16.1 16.5 Net Income 10.3 10.6 10.6 Balance Sheet Data: Current Assets 12.1 12.0 12.5 Noncurrent Assets 155.5 157.4 160.2 Current Liabilities 19.3 17.1 18.3 Noncurrent Liabilities 68.5 77.4 85.7 Total Members’ Equity 79.8 74.9 68.7 Contribution/Distribution Data: (1) Contributions to Hardy Storage — — — Distribution of earnings from Hardy Storage 2.6 2.2 3.1 Pennant Statement of Income Data: Net Revenues $ 34.6 $ 8.5 $ 2.0 Operating Income (Loss) 17.8 (2.4 ) 1.3 Net Income (Loss) 17.8 (2.4 ) 1.3 Balance Sheet Data: Current Assets 11.0 23.7 34.1 Noncurrent Assets 389.6 380.0 231.9 Current Liabilities 8.4 8.6 11.4 Total Members’ Equity 392.2 395.1 254.6 Contribution/Distribution Data: (1) Contributions to Pennant — 66.6 108.9 Distribution of earnings from Pennant 7.1 — — Return of capital from Pennant 16.0 — — (1) Contribution and distribution data represents CPG's portion based on CPG's ownership percentage of each investment.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The components of income tax expense were as follows: Year Ended December 31, (in millions) 2015 2014 2013 Predecessor Income Taxes Current Federal $ 12.1 $ 19.5 $ (15.5 ) State 9.1 7.6 (11.9 ) Total Current 21.2 27.1 (27.4 ) Deferred Federal 120.2 119.2 157.4 State 11.6 23.5 16.6 Total Deferred 131.8 142.7 174.0 Deferred Investment Credits — (0.1 ) (0.1 ) Total Income Taxes $ 153.0 $ 169.7 $ 146.5 Total income taxes from continuing operations were different from the amount that would be computed by applying the statutory federal income tax rate to book income before income tax. The major reasons for this difference were as follows: Year Ended December 31, (in millions) 2015 2014 2013 Predecessor Book income from Continuing Operations before income taxes $ 460.5 $ 438.4 $ 418.2 Tax expense at statutory federal income tax rate 161.2 35.0 % 153.5 35.0 % 146.4 35.0 % Increases (reductions) in taxes resulting from: State income taxes, net of federal income tax benefit 13.4 2.9 20.3 4.6 3.0 0.7 Noncontrolling interest (14.0 ) (3.0 ) — — — — AFUDC-Equity (9.2 ) (2.0 ) (3.7 ) (0.8 ) (2.4 ) (0.6 ) Other, net 1.6 0.3 (0.4 ) (0.1 ) (0.5 ) (0.1 ) Total Income Taxes $ 153.0 33.2 % $ 169.7 38.7 % $ 146.5 35.0 % The effective income tax rates were 33.2% , 38.7% and 35.0% in 2015 , 2014 and 2013 , respectively. The 5.5% decrease in the overall effective tax rate in 2015 versus 2014 was primarily due to income received following CPPL’s IPO that is not subject to income tax at the partnership level, as well as state income taxes, utility rate-making and other permanent book-to-tax differences. On December 18, 2015, the President signed into law the Protecting Americans from Tax Hikes Act of 2015 (PATH). PATH, among other things, permanently extends and modifies the research credit under Internal Revenue Code Section 41, and extends bonus depreciation (additional first-year depreciation) under a phase-down through 2019, as follows: • At 50% for 2015-2017; • At 40% in 2018; and • At 30% in 2019. In general, 50% bonus depreciation is available for qualified property placed in service in 2015, and in the following years, using the percentages above. CPG recorded the bonus depreciation effects of PATH for 2015 in the fourth quarter 2015. The permanent extension of the research credit did not have a significant effect on net income. On December 19, 2014, the President signed into law the Tax Increase Prevention Act ("TIPA"). TIPA extended and modified 50% bonus depreciation for 2014. CPG recorded the effects of TIPA in the fourth quarter 2014. In general, 50% bonus depreciation is available for property placed in service before January 1, 2015, or in the case of certain property having longer production periods, before January 1, 2016. The retroactive extension of the research credit did not have a significant effect on net income. On January 2, 2013, the President signed into law the American Taxpayer Relief Act of 2012 ("ATRA"). ATRA, among other things, extended retroactively the research credit under Internal Revenue Code section 41 until December 31, 2013, and also extended and modified 50% bonus depreciation for 2013. CPG recorded the effects of ATRA in the first quarter 2013. In November 2015, the FASB issued Accounting Standard Update (ASU) 2015-17 simplifying the presentation of accumulated deferred income taxes on the balance sheet. ASU 2015-17 eliminated the requirement to separate deferred tax liabilities and assets into a current amount and a noncurrent amount on the balance sheet. ASU 2015-17 simplifies the presentation of ADIT by requiring ADIT liabilities and ADIT assets be classified as noncurrent on the balance sheet. The FASB decided that the amendments in ASU 2015-17 can be applied either prospectively to all deferred tax liabilities and assets or retrospectively to all periods presented. The update is effective for annual periods, and interim periods within those annual periods, beginning after December 15, 2016 and earlier application is permitted. CPG’s Consolidated Balance Sheet reflects prospective early adoption of ASU 2015-17. The December 31, 2015 accumulated deferred income taxes is presented with application of ASU 2015-17, and is presented on the Consolidated Balance Sheet as a noncurrent liability. The December 31, 2014 balances were not restated. Deferred income taxes result from temporary differences between the financial statement carrying amounts and the tax basis of existing assets and liabilities. The principal components of CPG’s net deferred tax liability were as follows: At December 31, (in millions) 2015 2014 Deferred tax liabilities Accelerated depreciation and other property differences $ 1,429.2 $ 1,235.2 Pension and other postretirement/postemployment benefits 29.9 27.7 Other regulatory assets 71.8 62.8 Equity method investments 124.3 99.2 Total Deferred Tax Liabilities 1,655.2 1,424.9 Deferred tax assets Other regulatory liabilities (126.8 ) (116.7 ) Net operating loss carryforward (141.4 ) (70.3 ) Other (38.9 ) (42.2 ) Total Deferred Tax Assets (307.1 ) (229.2 ) Net Deferred Tax Liabilities 1,348.1 1,195.7 Less: Deferred income taxes related to current assets and liabilities — (60.0 ) Non-Current Deferred Tax Liability $ 1,348.1 $ 1,255.7 State income tax net operating loss benefits for West Virginia were recorded at their full value which CPG anticipates it is more likely than not that it will realize these benefits, prior to their expiration. The $127.7 million Federal carryforward will expire in various tax years from 2033 through 2035 and the $13.7 million state net operating loss benefit carryforward will expire in various tax years from 2028 through 2035 . The total amount of unrecognized tax benefits that, if recognized, would affect the effective tax rate is a $0.4 million decrease for December 31, 2015 , zero for December 31, 2014 and a $0.1 million increase for December 31, 2013 . CPG recognizes accrued interest on unrecognized tax benefits, accrued interest on other income tax liabilities, and tax penalties in income tax expense. No material amounts were recorded for the years ended December 31, 2015 , 2014 and 2013 , respectively. CPG is subject to income taxation in the United States and various state jurisdictions, primarily Indiana, West Virginia, Virginia, Pennsylvania, Kentucky, Louisiana, Mississippi, Maryland, Tennessee, New Jersey and New York. CPG was included in NiSource’s consolidated federal return prior to its separation from NiSource on July 1, 2015. Because NiSource is part of the IRS's Large and Mid-Size Business program, each year's federal income tax return is typically audited by the IRS. As of December 31, 2015 , federal income tax years through 2013 have been audited and are effectively closed to further assessment, except for immaterial carryforward amounts. The audit of NiSource’s 2014 and 2015 consolidated federal tax return began in 2014 and 2015, respectively. The statute of limitations in each of the state jurisdictions in which CPG operates remain open until the years are settled for federal income tax purposes, at which time amended state income tax returns reflecting all federal income tax adjustments are filed. As of December 31, 2015 , there were no state income tax audits in progress that would have a material impact on the consolidated and combined financial statements.

Pension And Other Postretiremen

Pension And Other Postretirement Benefits	12 Months Ended
	Dec. 31, 2015
Pension and Other Postretirement Benefit Expense [Abstract]
Pension and Other Postretirement Benefits Disclosure	Pension and Other Postretirement Benefits CPG provides defined contribution plans and noncontributory defined benefit retirement plans ("the CPG 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. As of July 1, 2015, in connection with the Separation, accrued pension and postretirement benefit obligations for CPG participants and related plan assets were transferred to CPG. CPG continues to follow multiple employer accounting following the Separation. Pension and Other Postretirement Benefit Plans’ Asset Management . CPG employs a total return investment approach whereby a mix of equities and fixed income investments are used to maximize the long-term return of plan assets for a prudent level of risk. Risk tolerance is established through careful consideration of plan liabilities, plan funded status, and asset class volatility. The investment portfolio contains a diversified blend of equity and fixed income investments. Furthermore, equity investments are diversified across U.S. and non-U.S. stocks, as well as growth, value, small and large capitalizations. Other assets such as private equity funds may be used judiciously to enhance long-term returns while improving portfolio diversification. Derivatives may be used to gain market exposure in an efficient and timely manner; however, derivatives may not be used to leverage the portfolio beyond the market value of the underlying assets. Investment risk is measured and monitored on an ongoing basis through quarterly investment portfolio reviews, annual liability measurements, and periodic asset/liability studies. To establish a long-term rate of return for plan assets assumption, past historical capital market returns and a proprietary forecast are evaluated. The long-term historical relationships between equities and fixed income are analyzed to ensure that they are consistent with the widely accepted capital market principle that assets with higher volatility generate greater return over the long run. Current market factors such as inflation and interest rates are evaluated before long-term capital market assumptions are determined. Peer data and historical returns are reviewed to check for reasonability and appropriateness. The most important component of an investment strategy is the portfolio asset mix, or the allocation between the various classes of securities available to the pension and other postretirement benefit plans for investment purposes. The asset mix and acceptable minimum and maximum ranges established for the CPG plan assets represents a long-term view and are listed in the following table. In 2012, an asset allocation policy for the pension fund was approved. This policy calls for a gradual reduction in the allocation to return-seeking assets (equities, real estate, private equity and hedge funds) and a corresponding increase in the allocation to liability-hedging assets (fixed income) as the funded status of the plans increase above 90% (as measured by the projected benefit obligations of the qualified pension plans divided by the market value of qualified pension plan assets). The asset mix and acceptable minimum and maximum ranges established by the policy for the pension fund at the pension plans funded status on December 31, 2015 are as follows: Asset Mix Policy of Funds: Defined Benefit Pension Plan Postretirement Benefit Plan Asset Category Minimum Maximum Minimum Maximum Domestic Equities 25% 45% 35% 55% International Equities 15% 25% 15% 25% Fixed Income 23% 37% 20% 50% Real Estate/Private Equity/Hedge Funds 0% 15% 0% 0% Short-Term Investments 0% 10% 0% 10% Pension Plan and Postretirement Plan Asset Mix at December 31, 2015 and December 31, 2014 : December 31, 2015 Defined Benefit Postretirement Asset Class Asset Value % of Total Assets Asset Value % of Total Assets (in millions) (in millions) Domestic Equities $ 141.0 39.4 % $ 101.6 44.4 % International Equities 62.5 17.5 % 42.8 18.8 % Fixed Income 123.3 34.4 % 76.6 33.6 % Cash/Other 31.0 8.7 % 7.2 3.2 % Total $ 357.8 100.0 % $ 228.2 100.0 % December 31, 2014 Defined Benefit Postretirement Asset Class Asset Value % of Total Assets Asset Value % of Total Assets (in millions) (in millions) Domestic Equities $ 144.2 41.1 % $ 105.7 47.2 % International Equities 63.3 18.1 % 41.2 18.4 % Fixed Income 120.9 34.4 % 76.3 34.1 % Real Estate/Private Equity/Hedge Funds 17.7 5.0 % — — % Cash/Other 4.9 1.4 % 0.6 0.3 % Total $ 351.0 100.0 % $ 223.8 100.0 % The categorization of investments into the asset classes in the table above are based on definitions established by the CPG Benefits Committee. Fair Value Measurements. The following table sets forth, by level within the fair value hierarchy, the CPG Pension Plan Trust and OPEB investment assets at fair value as of December 31, 2015 and 2014 . Assets and liabilities are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. Total CPG Pension Plan Trust and OPEB investment assets at fair value classified within Level 3 were zero and $17.6 million as of December 31, 2015 and December 31, 2014 , respectively. Such amounts were approximately zero and 3% of the CPG Pension Plan Trust and OPEB’s total investments as reported on the statement of net assets available for benefits at fair value as of December 31, 2015 and 2014 , respectively. Valuation Techniques Used to Determine Fair Value: Level 1 Measurements Most common and preferred stock are traded in active markets on national and international securities exchanges and are valued at closing prices on the last business day of each period presented. Cash is stated at cost which approximates their fair value, with the exception of cash held in foreign currencies which fluctuates with changes in the exchange rates. Government bonds, short-term bills and notes are priced based on quoted market values. Level 2 Measurements Most U.S. Government Agency obligations, mortgage/asset-backed securities, and corporate fixed income securities are generally valued by benchmarking model-derived prices to quoted market prices and trade data for identical or comparable securities. To the extent that quoted prices are not available, fair value is determined based on a valuation model that includes inputs such as interest rate yield curves and credit spreads. Securities traded in markets that are not considered active are valued based on quoted market prices, broker or dealer quotations, or alternative pricing sources with reasonable levels of price transparency. Other fixed income includes futures and options which are priced on bid valuation or settlement pricing. Commingled funds that hold underlying investments that have prices which are derived from the quoted prices in active markets are classified as Level 2. The funds' underlying assets are principally marketable equity and fixed income securities. Units held in commingled funds are valued at the unit value as reported by the investment managers. The fair value of the investments in commingled funds has been estimated using the net asset value per share of the investments. Level 3 Measurements Commingled funds that hold underlying investments that have prices which are not derived from the quoted prices in active markets are classified as Level 3. The respective fair values of these investments are determined by reference to the funds' underlying assets, which are principally marketable equity and fixed income securities. Units held in commingled funds are valued at the unit value as reported by the investment managers. These investments are often valued by investment managers on a periodic basis using pricing models that use market, income, and cost valuation methods. The hedge funds of funds invest in several strategies including fundamental long/short, relative value, and event driven. Hedge fund of fund investments may be redeemed annually, usually with 100 days' notice. Private equity investment strategies include buy-out, venture capital, growth equity, distressed debt, and mezzanine debt. Private equity investments are held through limited partnerships. Limited partnerships are valued at estimated fair market value based on their proportionate share of the partnership's fair value as recorded in the partnerships' audited financial statements. Partnership interests represent ownership interests in private equity funds and real estate funds. Real estate partnerships invest in natural resources, commercial real estate and distressed real estate. The fair value of these investments is determined by reference to the funds' underlying assets, which are principally securities, private businesses, and real estate properties. The value of interests held in limited partnerships, other than securities, is determined by the general partner, based upon third-party appraisals of the underlying assets, which include inputs such as cost, operating results, discounted cash flows and market based comparable data. Private equity and real estate limited partnerships typically call capital over a 3 to 5 year period and pay out distributions as the underlying investments are liquidated. The typical expected life of these limited partnerships is 10-15 years and these investments typically cannot be redeemed prior to liquidation. For the year ended December 31, 2015 , there were no significant changes to valuation techniques to determine the fair value of CPG's pension and other postretirement benefits' assets. Fair Value Measurements at December 31, 2015 : Fair Value Measurements (in millions) December 31, Quoted Prices in Active Significant Other Significant Pension plan assets Cash $ 0.9 $ 0.9 $ — $ — Equity securities International equities 6.6 6.6 — — Fixed income securities Government 8.5 — 8.5 — Corporate 13.0 — 13.0 — Commingled funds Short-term money markets 31.1 — 31.1 — U.S. equities 141.0 — 141.0 — International equities 55.6 — 55.6 — Fixed income 100.9 — 100.9 — Pension plan assets subtotal 357.6 7.5 350.1 — Other postretirement benefit plan assets Commingled funds Short-term money markets 7.3 — 7.3 — U.S. equities 13.9 — 13.9 — Mutual funds U.S. equities 87.7 87.7 — — International equities 42.8 42.8 — — Fixed income 76.5 76.5 — — Other postretirement benefit plan assets subtotal 228.2 207.0 21.2 — Due to brokers, net (1) (0.4 ) Accrued investment income/dividends 0.6 Total pension and other postretirement benefit plan assets $ 586.0 $ 214.5 $ 371.3 $ — (1) This class represents pending trades with brokers. The table below sets forth a summary of changes in the fair value of the Plan’s Level 3 assets for the year ended December 31, 2015 : (in millions) Balance at January 1, 2015 Total gains or losses (unrealized / realized) Purchases (Sales) Transfers into/(out of) level 3 Separation Allocation (1) Balance at December 31, 2015 Fixed income securities Other fixed income $ 0.1 $ — $ — $ — $ — $ (0.1 ) $ — Private equity limited partnerships U.S. multi-strategy 8.5 — — — — (8.5 ) — International multi-strategy 5.3 — — — — (5.3 ) — Distressed opportunities 1.1 — — — — (1.1 ) — Real estate 2.6 — — — — (2.6 ) — Total $ 17.6 $ — $ — $ — $ — (17.6 ) $ — (1) Level 3 assets were not contributed to the CPG Plans upon Separation from NiSource and no subsequent investments were made in Level 3 assets post Separation. Fair Value Measurements at December 31, 2014 : Fair Value Measurements (in millions) December 31, Quoted Prices in Active Significant Other Significant Pension plan assets Cash $ 2.6 $ 2.6 $ — $ — Equity securities U.S. equities 0.1 0.1 — — International equities 20.3 20.2 0.1 — Fixed income securities Government 17.8 15.7 2.1 — Corporate 38.7 — 38.7 — Mortgages/Asset backed securities 0.4 — 0.4 — Other fixed income 0.1 — — 0.1 Commingled funds Short-term money markets 4.9 — 4.9 — U.S. equities 144.2 — 144.2 — International equities 42.1 — 42.1 — Fixed income 61.6 — 61.6 — Private equity limited partnerships U.S. multi-strategy (1) 8.5 — — 8.5 International multi-strategy (2) 5.3 — — 5.3 Distressed opportunities 1.1 — — 1.1 Real Estate 2.6 — — 2.6 Pension plan assets subtotal 350.3 38.6 294.1 17.6 Other postretirement benefit plan assets Commingled funds Short-term money markets 0.8 — 0.8 — U.S. equities 14.3 — 14.3 — Mutual funds U.S. equities 91.3 91.3 — — International equities 41.2 41.2 — — Fixed income 76.2 76.2 — — Other postretirement benefit plan assets subtotal 223.8 208.7 15.1 — Due to brokers, net (3) (0.1 ) Accrued investment income/dividends 0.1 Net receivables 0.7 Total pension and other postretirement benefit plan assets $ 574.8 $ 247.3 $ 309.2 $ 17.6 (1) This class includes limited partnerships/fund of funds that invest in a diverse portfolio of private equity strategies, including buy-outs, venture capital, growth capital, special situations and secondary markets, primarily in the United States. (2) This class includes limited partnerships/fund of funds that invest in a diverse portfolio of private equity strategies, including buy-outs, venture capital, growth capital, special situations and secondary markets, primarily outside the United States. (3) This class represents pending trades with brokers. The table below sets forth a summary of changes in the fair value of the Plan’s Level 3 assets for the year ended December 31, 2014 : (in millions) Balance at January 1, 2014 Total gains or losses (unrealized / realized) Purchases (Sales) Transfers into/(out of) level 3 Balance at December 31, 2014 Fixed income securities Other fixed income $ — $ — $ 0.1 $ — $ — $ 0.1 Private equity limited partnerships U.S. multi-strategy 8.7 0.4 0.4 (1.0 ) — 8.5 International multi-strategy 5.8 (0.1 ) 0.1 (0.5 ) — 5.3 Distress opportunities 1.4 0.1 — (0.4 ) — 1.1 Real estate 3.0 0.3 — (0.7 ) — 2.6 Total $ 18.9 $ 0.7 $ 0.6 $ (2.6 ) $ — $ 17.6 Pension and Other Postretirement Benefit Plans’ Funded Status and Related Disclosure . The following table provides a reconciliation of the plans’ funded status and amounts reflected in CPG’s Consolidated Balance Sheets at December 31 based on a December 31 measurement date: Pension Benefits Other Postretirement Benefits (in millions) 2015 2014 2015 2014 Change in projected benefit obligation (1) Benefit obligation at beginning of year $ 397.6 $ 376.7 $ 124.2 $ 120.9 Service cost 5.9 4.8 1.0 1.1 Interest cost 15.0 15.7 4.7 5.2 Plan participants’ contributions — — 2.3 3.0 Actuarial loss (gain) (6.9 ) 22.7 (12.4 ) 5.7 Benefits paid (29.7 ) (22.3 ) (9.8 ) (12.4 ) Estimated benefits paid by incurred subsidy — — 0.3 0.7 Transfer of participant balances from NiSource plans (2) 22.6 — 1.8 — Projected benefit obligation at end of year $ 404.5 $ 397.6 $ 112.1 $ 124.2 Change in plan assets Fair value of plan assets at beginning of year $ 351.0 $ 344.5 $ 223.8 $ 209.7 Actual return on plan assets 1.2 21.1 (2.5 ) 11.6 Employer contributions 20.0 7.7 13.5 11.9 Plan participants’ contributions — — 2.3 3.0 Benefits paid (29.7 ) (22.3 ) (9.8 ) (12.4 ) Transfer of participant balances from NiSource plans (2) 15.3 — 0.9 — Fair value of plan assets at end of year $ 357.8 $ 351.0 $ 228.2 $ 223.8 Funded status at end of year $ (46.7 ) $ (46.6 ) $ 116.1 $ 99.6 Amounts recognized in the balance sheet consist of: Noncurrent assets $ — $ — $ 116.1 $ 113.1 Current liabilities (0.8 ) — — — Noncurrent liabilities (45.9 ) (46.6 ) — (13.5 ) Net amount recognized at end of year (3) $ (46.7 ) $ (46.6 ) $ 116.1 $ 99.6 Amounts recognized in AOCI or regulatory assets/liabilities (4) Unrecognized prior service credit $ (3.7 ) $ (4.7 ) $ (2.0 ) $ (2.6 ) Unrecognized actuarial loss (gain) 164.5 148.7 (3.9 ) (12.5 ) Total recognized AOCI or regulatory assets/liabilities $ 160.8 $ 144.0 $ (5.9 ) $ (15.1 ) (1) The change in benefit obligation for Pension Benefits represents the change in Projected Benefit Obligation while the change in benefit obligation for Other Postretirement Benefits represents the change in Accumulated Postretirement Benefit Obligation. (2) Reflects the transfer of additional pension and OPEB plan participants to CPGSC upon Separation from NiSource that were determined in the current year. (3) CPG recognizes in its Consolidated Balance Sheets the underfunded and overfunded status of its various defined benefit postretirement plans, measured as the difference between the fair value of the plan assets and the benefit obligation. (4) CPG determined that the future recovery of pension and other postretirement benefits costs is probable. CPG recorded regulatory assets and liabilities of $135.2 million and $0.7 million , respectively, as of December 31, 2015 , and $120.9 million and $8.3 million , respectively, as of December 31, 2014 that would otherwise have been recorded to accumulated other comprehensive loss. CPG’s accumulated benefit obligation for its pension plans was $404.5 million and $397.6 million as of December 31, 2015 and 2014 , respectively. The accumulated benefit obligation as of a date is the actuarial present value of benefits attributed by the pension benefit formula to employee service rendered prior to that date and based on current and past compensation levels. CPG's pension plans were underfunded by $46.7 million at December 31, 2015 , compared to being underfunded by $46.6 million at December 31, 2014 . CPG contributed $20.0 million and $7.7 million to its pension plans in 2015 and 2014 , respectively. During 2015 , CPG’s funded status for its other postretirement benefit plans improved by $16.5 million to an overfunded status of $116.1 million primarily due to favorable claims experience and the implementation of new mortality assumptions released by the Society of Actuaries in 2014, offset by unfavorable asset returns. CPG contributed approximately $13.5 million and $11.9 million to its other postretirement benefit plans in 2015 and 2014 , respectively. No amounts of CPG’s pension or other postretirement benefit plans’ assets are expected to be returned to CPG or any of its subsidiaries in 2016 . In 2013, NiSource pension plans had year to date lump sum payouts exceeding the plans' 2013 service cost plus interest cost and, therefore, settlement accounting was required. As a result, the Predecessor recorded a settlement charge of $13.8 million in 2013. The Predecessor's net periodic pension benefit cost for 2013 was decreased by $1.3 million as a result of the interim remeasurements. The following table provides the key assumptions that were used to calculate the pension and other postretirement benefits obligations for CPG’s various plans as of December 31: Pension Benefits Other Postretirement Benefits 2015 2014 2015 2014 Weighted-average assumptions to Determine Benefit Obligation Discount Rate 4.05 % 3.64 % 4.29 % 3.96 % Rate of Compensation Increases 4.00 % 4.00 % Health Care Trend Rates Trend for Next Year 8.39 % 6.90 % Ultimate Trend 4.50 % 4.50 % Year Ultimate Trend Reached 2022 2021 Assumed health care cost trend rates have a significant effect on the amounts reported for the health care plans. A one-percentage-point change in assumed health care cost trend rates would have the following effects: (in millions) 1% point increase 1% point decrease Effect on service and interest components of net periodic cost $ 0.1 $ (0.1 ) Effect on accumulated postretirement benefit obligation 3.1 (2.8 ) CPG expects to make contributions of approximately $0.8 million to its pension plans and approximately $2.2 million to its postretirement medical and life plans in 2016 . The following table provides benefits expected to be paid in each of the next five fiscal years, and in the aggregate for the five fiscal years thereafter. The expected benefits are estimated based on the same assumptions used to measure CPG's benefit obligation at the end of the year and includes benefits attributable to the estimated future service of employees: (in millions) Pension Benefits Other Federal Year(s) 2016 $ 34.9 $ 8.2 $ 0.6 2017 33.9 8.0 0.6 2018 35.1 8.0 0.6 2019 35.8 7.9 0.6 2020 37.1 7.9 0.5 2021-2025 175.3 37.4 1.7 The following table provides the components of the plans’ net periodic benefits cost for each of the three years ended December 31, 2015 , 2014 and 2013 : Pension Benefits Other Postretirement Benefits (in millions) 2015 2014 2013 2015 2014 2013 Predecessor Predecessor Components of Net Periodic Benefit Cost (Income) Service cost $ 5.9 $ 4.8 $ 4.9 $ 1.0 $ 1.1 $ 1.5 Interest cost 15.0 15.7 14.6 4.7 4.6 5.4 Expected return on assets (28.2 ) (27.3 ) (25.5 ) (18.1 ) (16.6 ) (13.8 ) Amortization of prior service (credit) cost (1.1 ) (1.1 ) (1.1 ) (0.3 ) 0.1 0.1 Recognized actuarial loss (gain) 9.9 7.5 12.3 (0.3 ) — 1.0 Net Periodic Benefit Cost (Income) 1.5 (0.4 ) 5.2 (13.0 ) (10.8 ) (5.8 ) Settlement loss — — 13.8 — — — Total Net Periodic Benefit Cost (Income) $ 1.5 $ (0.4 ) $ 19.0 $ (13.0 ) $ (10.8 ) $ (5.8 ) The $1.9 million increase in the actuarially-determined pension benefit cost (income) is due primarily to the transfer of additional pension plan participants to CPGSC upon Separation from NiSource, decreased discount rates and unfavorable asset returns in 2015 compared to 2014 . For its other postretirement benefit plans, CPG recognized $13.0 million in net periodic benefit income in 2015 compared to net periodic benefit income of $10.8 million in 2014 due primarily to favorable claims experience, offset by a decrease in discount rates in 2015 compared to 2014 . The following table provides the key assumptions that were used to calculate the net periodic benefits cost for CPG’s various plans: Pension Benefits Other Postretirement Benefits 2015 2014 2013 2015 2014 2013 Predecessor Predecessor Weighted-average Assumptions to Determine Net Periodic Benefit Cost Discount Rate 3.84 % 4.34 % 3.36 % 4.10 % 4.76 % 3.92 % Expected Long-Term Rate of Return on Plan Assets 8.20 % 8.30 % 8.30 % 8.05 % 8.14 % 8.17 % Rate of Compensation Increases 4.00 % 4.00 % 4.00 % CPG believes it is appropriate to assume an 8.20% and 8.05% rate of return on pension and other postretirement plan assets, respectively, for its calculation of 2015 pension benefits cost. This is primarily based on asset mix and historical rates of return. The following table provides other changes in plan assets and projected benefit obligations recognized in other comprehensive income or regulatory asset or liability: Pension Benefits Other Postretirement Benefits (in millions) 2015 2014 2015 2014 Other changes in plan assets and projected benefit obligations recognized in other comprehensive income or regulatory assets or liabilities Net actuarial loss $ 25.6 $ 28.9 $ 8.6 $ 11.8 Less: amortization of prior service (credit) cost 1.1 1.1 0.3 (0.1 ) Less: amortization of net actuarial (gain) loss (9.9 ) (7.5 ) 0.3 — Total recognized in other comprehensive income or regulatory assets or liabilities $ 16.8 $ 22.5 $ 9.2 $ 11.7 Amount recognized in net periodic benefit cost and other comprehensive income or regulatory assets or liabilities $ 18.3 $ 22.1 $ (3.8 ) $ 0.9 Based on a December 31 measurement date, the net unrecognized actuarial loss, unrecognized prior service cost (credit), and unrecognized transition obligation that will be amortized into net periodic benefit cost during 2016 for the pension plans are $12.4 million , $(1.2) million and zero , respectively, and for other postretirement benefit plans are $0.2 million , $(0.7) million and zero , respectively.

Fair Value

Fair Value	12 Months Ended
	Dec. 31, 2015
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, short-term borrowings and short-term borrowings-affiliated. CPG’s long-term debt and long-term debt-affiliated are 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 and Long-term debt-affiliated . The fair values of these securities are estimated based on the quoted market prices for similar issues or on the rates offered for securities of the same remaining maturities. These fair value measurements are classified as Level 2 within the fair value hierarchy. For the years ended December 31, 2015 and 2014 , there were no changes in the method or significant assumptions used to estimate the fair value of the financial instruments. The carrying amount and estimated fair values of financial instruments were as follows: At December 31, (in millions) Carrying Amount 2015 Estimated Fair Value 2015 Carrying Amount 2014 Estimated Fair Value 2014 Current portion of long-term debt - affiliated $ — $ — $ 115.9 $ 120.0 Long-term debt 2,746.2 2,592.1 — — Long-term debt - affiliated — — 1,472.8 1,550.4

Authorized Preferred Stock

Authorized Preferred Stock	12 Months Ended
	Dec. 31, 2015
Equity [Abstract]
Authorized Preferred Stock	Authorized Preferred Stock CPG has 80,000,000 authorized shares of preferred stock with a $0.01 par value. As of December 31, 2015 , CPG had no preferred shares outstanding. All of CPG's retained earnings at December 31, 2015 are free of restrictions.

Common Stock

Common Stock	12 Months Ended
	Dec. 31, 2015
Equity [Abstract]
Common Stock	Common Stock As of December 31, 2015 , CPG had 2,000,000,000 authorized shares of common stock with a $0.01 par value. Common Stock Offering. On December 7, 2015 , CPG completed the sale of 82,225,000 shares of common stock, including 10,725,000 shares of common stock that were issued pursuant to the exercise in full of the underwriters' over-allotment option. CPG received net proceeds of $1,394.7 million , net of underwriting discounts and estimated offering expenses of approximately $44.2 million . Common Stock Dividends. Holders of shares of CPG's common stock are entitled to receive dividends when, as and if declared by the board of directors out of funds legally available for that purpose. CPG paid quarterly common dividends totaling $0.25 per share for the year ended December 31, 2015 . At its January 29, 2016 meeting, the board of directors declared a $0.12875 per share quarterly common dividend, payable on February 19, 2016 to holders of record on February 8, 2016 .

Share-Based Compensation

Share-Based Compensation	12 Months Ended
	Dec. 31, 2015
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 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 December 31, 2015 , there were 5,513,260 shares reserved for future awards under the Omnibus Plan. CPG recognized stock-based employee compensation expense of $7.9 million , $4.4 million and $1.1 million , during 2015 , 2014 and 2013 , respectively, as well as related tax benefits of $2.9 million , $1.6 million and $0.4 million , respectively. As of December 31, 2015 , the total remaining unrecognized compensation cost related to nonvested awards amounted to $21.0 million , which will be amortized over the weighted-average remaining requisite service period of 2.0 years. Restricted Stock Units and Restricted Stock . In 2015 , CPG granted restricted stock units and shares of restricted stock of 130,160 , subject to service conditions. The total grant date fair value of the shares of restricted stock units and shares of restricted stock was $3.6 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 December 31, 2015 , 129,665 nonvested (all of which are expected to vest) restricted stock units and shares of restricted stock were granted and outstanding for the 2015 award. In 2015 , NiSource granted restricted stock units and shares of restricted stock that were converted into 450,107 CPG restricted stock units at Separation, subject to service conditions. The total grant date fair value of the shares of restricted stock units and shares of restricted stock was $11.6 million , based on the average market price of NiSource’s common stock at the date of each grant less the present value of any dividends not received during the vesting period converted into CPG common stock awards, which will be expensed, net of forfeitures, over the vesting period which is generally three years. As of December 31, 2015 , 450,107 nonvested (all of which are expected to vest) restricted stock units and shares of restricted stock were granted and outstanding for the 2015 award. In 2014 , NiSource granted restricted stock units and shares of restricted stock that were converted into 198,532 CPG restricted stock units at Separation, subject to service conditions. The total grant date fair value of the restricted stock units and shares of restricted stock was $4.2 million , based on the average market price of NiSource’s common stock at the date of each grant less the present value of dividends not received during the vesting period converted into CPG common stock awards, which will be expensed, net of forfeitures, over the vesting period which is generally three years. As of December 31, 2015 , 198,532 nonvested (all of which are expected to vest) restricted stock units and shares of restricted stock were granted and outstanding for the 2014 award. In 2013 , NiSource granted restricted stock units and shares of restricted stock that were converted into 31,655 CPG restricted stock units at Separation, subject to service conditions. The total grant date fair value of the restricted stock units and shares of restricted stock was $0.5 million , based on the average market price of NiSource’s common stock at the date of each grant less the present value of dividends not received during the vesting period converted into CPG common stock awards, which will be expensed, net of forfeitures, over the vesting period which is generally three years. As of December 31, 2015 , 30,087 nonvested (all of which are expected to vest) restricted stock units and shares of restricted stock were granted and outstanding for the 2013 award. If the employee terminates employment before the service conditions lapse under the 2013 , 2014 and 2015 awards due to (1) Retirement or Disability (as defined in the award agreement), or (2) death, the service conditions will lapse on the date of such termination with respect to a pro rata portion of the restricted stock units and shares of restricted stock. In the event of a Change-in-Control (as defined in the award agreement), all unvested shares of restricted stock and restricted stock units awarded prior to 2015 will immediately vest upon termination of employment occurring in connection with a change-in-control. Termination due to any other reason will result in all unvested shares of restricted stock and restricted stock units awarded being forfeited effective on the employee's date of termination. Restricted Stock Units Weighted Average Grant Date Fair Value Nonvested at December 31, 2014 230,187 $ 20.27 Performance shares converted to restricted shares at Separation 1,460,401 15.66 Granted 580,267 26.29 Forfeited (495 ) 28.25 Vested (1,568 ) 18.24 Nonvested and Expected to Vest at December 31, 2015 2,268,792 $ 18.85 Performance Shares . In 2015 , CPG granted 161,504 performance shares subject to performance and service conditions. The grant date fair-value of the awards was $4.5 million , based on the average market price of CPG’s common stock at the date of the 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 condition is based on achievement of relative total stockholder return, a non-GAAP financial measure that CPG defines as the annualized growth in dividends and share price as a share of CPG's common stock (calculated using a 20 trading day average of CPG's closing price, over a period beginning July 31, 2015 and ending on June 30, 2018) compared to the total stockholder return performance of a predetermined peer group of companies. The service conditions lapse on July 12, 2018 when the shares vest provided the performance criteria is satisfied. As of December 31, 2015 , 161,504 nonvested performance shares were granted and outstanding of the 2015 award. In 2014 , NiSource granted performance shares that were converted to 586,219 CPG restricted stock units at Separation, subject to performance and service conditions. The grant date fair-value of the awards was $11.3 million , based on the average market price of NiSource’s common stock at the date of each 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. Through the conversion, the performance contingencies were removed from these awards. The service conditions lapse on February 28, 2017, when the shares vest. As of December 31, 2015 , 586,219 nonvested (all of which are expected to vest) restricted stock units and shares of restricted stock were granted and outstanding for the 2014 award. In 2013 , NiSource granted performance shares that were converted to 874,182 CPG restricted stock units at Separation, subject to performance and service conditions. The grant date fair-value of the awards was $11.6 million , based on the average market price of NiSource’s common stock at the date of each 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. Through the conversion, the performance contingencies were removed from these awards. The service conditions lapsed on January 30, 2016 when the shares vested. As of December 31, 2015 , 874,182 nonvested (all of which are expected to vest) restricted stock units and shares of restricted stock were granted and outstanding for the 2013 award. If the employee terminates employment before the performance and service conditions lapse under the 2013 , 2014 and 2015 awards due to (1) Retirement or Disability (as defined in the award agreement), or (2) death, the employment conditions will lapse with respect to a pro rata portion of the performance shares payable at target on the date of termination provided the performance criteria are met. In the event of a Change-in-Control (as defined in the award agreement), all unvested performance shares will immediately vest. Termination due to any other reason will result in all performance shares awarded being forfeited effective on the employee’s date of termination. Contingent Awards Weighted Average Grant Date Fair Value Nonvested at December 31, 2014 1,460,401 $ 15.66 Performance shares converted to restricted shares at Separation (1,460,401 ) 15.66 Granted 161,504 28.16 Forfeited — — Vested — — Nonvested and Expected to Vest at December 31, 2015 161,504 $ 28.16 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 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 December 31, 2015 , a total of 52,035 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 30,636 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 December 31, 2015 , 226,908 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 payable in shares of common stock to eligible employees based on earnings results; and eligible employees hired after January 1, 2010, receive a non-elective company contribution of three percent of eligible pay. For the years ended December 31, 2015 , 2014 and 2013 , CPG recognized 401(k) match, profit sharing and non-elective contribution expense of $9.8 million , $8.4 million and $6.1 million , respectively.

Other Commitments And Contingen

Other Commitments And Contingencies	12 Months Ended
	Dec. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Other Commitments And Contingencies	Other Commitments and Contingencies A. Guarantees and Indemnities. In the normal course of 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 December 31, 2015 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 45.7 0.6 2.0 — — — 43.1 Total commercial commitments $ 63.8 $ 18.7 $ 2.0 $ — $ — $ — $ 43.1 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 December 31, 2015 , 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 December 31, 2015 , 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 December 31, 2015 , CPG had no Promissory Notes outstanding under the Program. Other Guarantees or Obligations. CPG has purchase and sale agreement guarantees totaling $45.7 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 Consolidated Balance Sheets. 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 December 31, 2015 . 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 consolidated financial statements. B. Tax Matters . CPG records liabilities for potential income tax assessments. The accruals relate to tax positions in a variety of taxing jurisdictions and are based on CPG’s estimate of the ultimate resolution of these positions. These liabilities may be affected by changing interpretations of laws, rulings by tax authorities, or the expiration of the statute of limitations. CPG was included in NiSource's consolidated federal return for tax years prior to December 31, 2014 and will be included in NiSource's consolidated 2015 federal return through July 1, 2015. NiSource is part of the IRS Large and Mid-Size Business program. As a result, each year’s federal income tax return is typically audited by the IRS. As of December 31, 2015, tax years through 2013 have been audited and are effectively closed to further assessment, except for immaterial carryforward amounts. The audit of tax years 2014 and 2015 under the Compliance Assurance Program (“CAP”) is in process. As of December 31, 2015, there were no state income tax audits in progress that would have a material impact on the consolidated and combined financial statements. CPG is currently being audited for sales and use tax compliance in the state of Louisiana, New York, Ohio, and West Virginia. None of these sales and use tax audits are expected to have a material impact on the consolidated and combined 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 December 31, 2015 and 2014 , CPG has liabilities recorded of approximately $8.3 million and $14.3 million , respectively, to cover environmental remediation at various sites. The current portion of these liabilities is included in “Other accruals” in the Consolidated Balance Sheets. The noncurrent portion is included in “Other noncurrent liabilities” in the Consolidated Balance Sheets. 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. The EPA has already promulgated regulations requiring the monitoring and reporting of GHG emissions from, among other sources, certain onshore natural gas transmission and storage facilities, including gathering and boosting facilities, completions and workovers of oil wells with hydraulic fracturing, and blowdowns of natural gas transmission pipelines between compressor stations, in the U.S. on an annual basis. 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. 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 $6.5 million and $12.5 million at December 31, 2015 and 2014 , 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 December 31, 2015 and 2014 . The liability represents CPG's best estimate of the cost to remediate the facilities. D. Operating Lease Commitments. CPG leases assets in several areas of its operations. Payments made in connection with operating leases were $21.2 million in 2015 , $14.9 million in 2014 and $13.3 million in 2013 , and are primarily charged to operation and maintenance expense as incurred. Future minimum rental payments required under operating and capital leases that have initial or remaining non-cancelable lease terms in excess of one year are: (in millions) Operating Leases (1) 2016 $ 5.4 2017 6.7 2018 6.2 2019 5.5 2020 5.4 After 24.7 Total future minimum payments $ 53.9 (1) Operating lease expense includes amounts for fleet leases and storage well leases that can be renewed beyond the initial lease term, but the anticipated payments associated with the renewals do not meet the definition of expected minimum lease payments and, therefore, are not included above. E. Service Obligations . CPG has entered into various service agreements whereby CPG is contractually obligated to make certain minimum payments in future periods. CPG has pipeline service agreements that provide for pipeline capacity, transportation and storage services. These agreements, which have expiration dates ranging from 2016 to 2025, require CPG to pay fixed monthly charges. On June 15, 2015 , CPG entered into a five-year IT services agreement including cloud, mobile, analytics and security technologies with IBM. The agreement became effective with the closing of the Separation on July 1, 2015 , with tiered commencement dates by service line. Under the agreement, at December 31, 2015, CPG expects to pay approximately $165.3 million to IBM in service fees as shown in the table below. Upon any termination of the agreement by CPG for any reason (other than material breach by IBM), CPG may be required to pay IBM a termination charge that could include a breakage fee, repayment of IBM's capital investments not yet recovered and IBM's wind-down expense. This termination fee could be material depending on the events giving rise to the termination and the timing of the termination. The estimated aggregate amounts of minimum fixed payments at December 31, 2015 , were: (in millions) Pipeline Service Agreements IBM Service Agreement 2016 $ 51.5 $ 38.6 2017 49.5 33.0 2018 42.0 31.7 2019 25.4 31.0 2020 24.2 31.0 After 66.8 — Total future minimum payments $ 259.4 $ 165.3

Accumulated Other Comprehensive

Accumulated Other Comprehensive Loss	12 Months Ended
	Dec. 31, 2015
Components of Accumulated Other Comprehensive Income (Loss) [Abstract]
Accumulated Other Comprehensive Loss	Accumulated Other Comprehensive Loss The following table displays the activity of Accumulated Other Comprehensive Loss, net of tax: (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, 2013 - Predecessor $ (18.7 ) $ (16.4 ) $ (35.1 ) Other comprehensive income before reclassifications — 6.5 6.5 Amounts reclassified from accumulated other comprehensive income 1.1 1.7 2.8 Net current-period other comprehensive income 1.1 8.2 9.3 Balance as of December 31, 2013 - Predecessor $ (17.6 ) $ (8.2 ) $ (25.8 ) Other comprehensive income before reclassifications — (9.3 ) (9.3 ) Amounts reclassified from accumulated other comprehensive income 1.0 (0.4 ) 0.6 Net current-period other comprehensive income 1.0 (9.7 ) (8.7 ) Balance as of December 31, 2014 $ (16.6 ) $ (17.9 ) $ (34.5 ) Other comprehensive income before reclassifications (0.9 ) 5.0 4.1 Amounts reclassified from accumulated other comprehensive income 1.1 0.2 1.3 Net current-period other comprehensive income 0.2 5.2 5.4 Allocation of accumulated other comprehensive loss to noncontrolling interest 2.1 — 2.1 Balance as of December 31, 2015 $ (14.3 ) $ (12.7 ) $ (27.0 ) (1) All amounts are net of tax. Amounts in parentheses indicate debits. Equity Method Investment During 2008, Millennium Pipeline, in which CPG has an equity investment, entered into three interest rate swap agreements with a notional amount totaling $420.0 million with seven counterparties. During August 2010, Millennium Pipeline completed the refinancing of its long-term debt, securing permanent fixed-rate financing through the private placement issuance of two tranches of notes totaling $725.0 million , $375.0 million at 5.33% due June 30, 2027 and $350.0 million at 6.00% due June 30, 2032 . Upon the issuance of these notes, Millennium Pipeline repaid all outstanding borrowings under its credit agreement, terminated the sponsor guarantee, and cash settled the interest rate hedges. These interest rate swap derivatives were primarily accounted for as cash flow hedges by Millennium Pipeline. As an equity method investment, CPG is required to recognize a proportional share of Millennium Pipeline’s OCI. The remaining unrecognized loss of $14.3 million , net of tax, related to these 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 $14.3 million and $16.6 million at December 31, 2015 and December 31, 2014 , respectively, is included in unrealized losses on cash flow hedges above.

Other, Net

Other, Net	12 Months Ended
	Dec. 31, 2015
Other Nonoperating Income (Expense) [Abstract]
Other, Net	Other, Net Year Ended December 31, (in millions) 2015 2014 2013 Predecessor AFUDC Equity $ 28.3 $ 11.0 $ 6.8 Miscellaneous (1) 1.0 (2.2 ) 11.1 Total Other, net $ 29.3 $ 8.8 $ 17.9 (1) Miscellaneous primarily consists of a gain from insurance proceeds in 2013.

Interest Expense

Interest Expense	12 Months Ended
	Dec. 31, 2015
Interest Expense [Abstract]
Interest Expense	Interest Expense Year Ended December 31, (in millions) 2015 2014 2013 Predecessor Interest on long-term debt $ 67.5 $ — $ — Interest on short-term borrowings (1) 1.4 — — Debt discount/cost amortization 3.1 — — Allowance for funds used during construction (6.8 ) — — Other 2.4 — — Total Interest Expense (2) $ 67.6 $ — $ — (1) Refer to Note 5, "Short-Term Borrowings" for additional information. (2) Refer to Note 4, "Transactions with Affiliates" for a discussion of interest expense-affiliated for the year ended December 31, 2014 and 2013 .

Segments Of Business

Segments Of Business	12 Months Ended
	Dec. 31, 2015
Segment Reporting [Abstract]
Segments Of Business	Segments of Business Operating segments are components of an enterprise for which separate financial information is available and evaluated regularly by the chief operating decision maker in deciding how to allocate resources and assess performance. The CPG Chief Executive Officer is the chief operating decision maker for the periods presented. At December 31, 2015 , CPG's operations comprise one operating segment. CPG's segment offers gas transportation and storage services for LDCs, marketers 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 and development of mineral rights positions. The chief operating decision maker evaluates the performance of CPG operations and determines how to allocate resources on a consolidated basis.

Supplemental Cash Flow Informat

Supplemental Cash Flow Information	12 Months Ended
	Dec. 31, 2015
Supplemental Cash Flow Information [Abstract]
Supplemental Cash Flow Information	Supplemental Cash Flow Information The following tables provide additional information regarding the CPG’s Statements of Consolidated and Combined Cash Flows for the years ended December 31, 2015 , 2014 and 2013 : Year Ended December 31, (in millions) 2015 2014 2013 Predecessor Supplemental Disclosures of Cash Flow Information Non-cash transactions: Capital expenditures included in current liabilities (1) $ 128.4 $ 78.5 $ 53.1 Schedule of interest and income taxes paid: Cash paid for interest, net of interest capitalized amounts $ 96.9 $ 53.6 $ 38.4 Cash paid for income taxes (2) 32.3 21.2 15.3 (1) Capital expenditures included in current liabilities is comprised of "Accrued capital expenditures" and certain other amounts included within "Accounts payable" on the Consolidated Balance Sheets. (2) Cash paid for income taxes for the year ended December 31, 2015 includes $20.9 million paid to NiSource under the Tax Allocation Agreement.

Concentration of Credit Risk

Concentration of Credit Risk	12 Months Ended
	Dec. 31, 2015
Risks and Uncertainties [Abstract]
Concentration of Credit Risk	Concentration of Credit Risk Columbia Gas of Ohio, an affiliated party prior to the Separation, accounted for greater than 10% of total operating revenues in the years ended December 31, 2015 , 2014 and 2013 . The following table provides this customer's operating revenues and percentage of total operating revenues for the years ended December 31, 2015 , 2014 and 2013 : Year Ended December 31, 2015 2014 2013 (in millions) Total Operating Revenues Percentage of Total Operating Revenues Total Operating Revenues Percentage of Total Operating Revenues Total Operating Revenues Percentage of Total Operating Revenues Predecessor Columbia Gas of Ohio (1) $ 167.3 12.5 % $ 168.5 12.5 % $ 167.5 14.2 % (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 agreements 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 would have a material adverse effect on the business of CPG.

Quarterly Financial Data (Unaud

Quarterly Financial Data (Unaudited)	12 Months Ended
	Dec. 31, 2015
Quarterly Financial Data [Abstract]
Quarterly Financial Data	Quarterly Financial Data (Unaudited) (in millions, except per unit data) First Quarter Second Quarter Third Quarter Fourth Quarter 2015 Total Operating Revenues $ 340.0 $ 316.1 $ 320.9 $ 357.9 Operating Income 162.7 107.3 135.9 122.2 Income from Continuing Operations 97.1 60.1 74.9 75.4 Results from Discontinued Operations - net of taxes — (0.3 ) (0.1 ) — Net Income attributable to CPG 90.0 50.8 63.0 63.4 Basic Earnings Per Share Continuing Operations 0.28 0.16 0.20 0.19 Discontinued Operations — — — — Basic Earnings Per Share $ 0.28 $ 0.16 $ 0.20 $ 0.19 Diluted Earnings Per Share Continuing Operations 0.28 0.16 0.20 0.19 Discontinued Operations — — — — Diluted Earnings Per Share $ 0.28 $ 0.16 $ 0.20 $ 0.19 2014 Total Operating Revenues $ 345.8 $ 343.5 $ 318.0 $ 340.7 Operating Income 159.1 103.9 94.5 134.1 Income from Continuing Operations 93.0 59.4 53.7 62.6 Results from Discontinued Operations - net of taxes (0.2 ) (0.3 ) (0.1 ) — Net Income attributable to CPG 92.8 59.1 53.6 62.6 Basic Earnings Per Share Continuing Operations 0.29 0.19 0.17 0.20 Discontinued Operations — — — — Basic Earnings Per Share $ 0.29 $ 0.19 $ 0.17 $ 0.20 Diluted Earnings Per Share Continuing Operations 0.29 0.19 0.17 0.20 Discontinued Operations — — — — Diluted Earnings Per Share $ 0.29 $ 0.19 $ 0.17 $ 0.20

Nature Of Operations And Summ36

Nature Of Operations And Summary Of Significant Accounting Policies (Policy)	12 Months Ended
	Dec. 31, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Company Structure And Principles Of Consolidation	Company Structure and Basis of Presentation . Columbia Pipeline Group, Inc. ("CPG") is a growth-oriented Delaware corporation formed by NiSource Inc. ("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. All periods prior to September 26, 2014 reflect the combined financial position, results of operations and cash flows for CPG's Predecessor (the "Predecessor"). 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 did 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. CPG’s accompanying Consolidated and Combined Financial Statements have been prepared in accordance with GAAP. 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. Also included in the Consolidated and Combined Financial Statements are equity method investments Hardy Storage, Millennium Pipeline, and Pennant. All intercompany transactions and balances have been eliminated.
Use Of Estimates	Use of Estimates. The preparation of financial statements in conformity with accounting principles generally accepted in the United States requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.
Cash And Cash Equivalents	Cash and Cash Equivalents. Cash and cash equivalents are liquid marketable securities with an original maturity date of less than three months.
Allowance For Uncollectible Accounts	Allowance for Uncollectible Accounts. The reserve for uncollectible receivables is CPG's best estimate of the amount of probable credit losses in the existing accounts receivable. Collectability of accounts receivable is reviewed regularly and an allowance is established or adjusted, as necessary, using the specific identification method. Account balances are charged against the allowance when it is anticipated the receivable will not be recovered.
Basis Of Accounting For Rate-Regulated Subsidiaries	Basis of Accounting for Rate-Regulated Subsidiaries . Rate-regulated subsidiaries account for and report assets and liabilities consistent with the economic effect of the way in which regulators establish rates, if the rates established are designed to recover the costs of providing the regulated service and it is probable that such rates can be charged and collected. Certain expenses and credits subject to utility regulation or rate determination normally reflected in income are deferred on the Consolidated Balance Sheets and are recognized in income as the related amounts are included in service rates and recovered from or refunded to customers. In the event that regulation significantly changes the opportunity for CPG to recover its costs in the future, all or a portion of CPG’s regulated operations may no longer meet the criteria for regulatory accounting. In such an event, a write-down of all or a portion of CPG’s existing regulatory assets and liabilities could result. If CPG is unable to continue to apply the provisions of regulatory accounting, CPG would be required to apply the provisions of Discontinuation of Rate-Regulated Accounting. In management’s opinion, CPG’s regulated subsidiaries will be subject to regulatory accounting for the foreseeable future. Please see Note 11, "Regulatory Matters," in the Notes to Consolidated and Combined Financial Statements for further discussion.
Property, Plant And Equipment And Related AFUDC and Maintenance	Property, Plant and Equipment and Related AFUDC and Maintenance . Property, plant and equipment is stated at cost. CPG's rate-regulated subsidiaries record depreciation using composite rates on a straight-line basis over the remaining service lives of the properties as approved by the appropriate regulators. CPG's non-regulated companies depreciate assets on a component basis on a straight-line basis over the remaining service lives of the properties. CPG capitalizes AFUDC on all classes of property except organization costs, land, autos, office equipment, tools and other general property purchases. The allowance is applied to construction costs for that period of time between the date of the expenditure and the date on which such project is placed in service. A combination of short-term borrowings, long-term debt and equity were used to fund construction efforts for all three years presented. The pre-tax rate for AFUDC debt and ADUFC equity are summarized in the table below: 2015 2014 2013 Debt Equity Debt Equity Debt Equity Predecessor Columbia Gas Transmission 1.8 % 6.3 % 0.9 % 3.0 % 2.5 % 3.2 % Columbia Gulf 2.9 % 6.3 % 2.1 % 9.4 % 2.5 % 3.2 % CPG follows the practice of charging maintenance and repairs, including the cost of removal of minor items of property, to expense as incurred. When regulated property that represents a retired unit is replaced or removed, the cost of such property is credited to utility plant, and such cost, net of salvage, is charged to the accumulated provision for depreciation in accordance with composite depreciation.
Gas-Stored Base Gas	Gas Stored-Base Gas. Base gas, which is valued at original cost, represents storage volumes that are maintained to ensure that adequate well pressure exists to deliver current gas inventory. There were no purchases of base gas during the years ended December 31, 2015 , 2014 and 2013 . Please see Note 7, "Gain on Sale of Assets," in the Notes to Consolidated and Combined Financial Statements for information regarding the sale of storage base gas in 2013 . Gas stored-base gas is included in Property, plant and equipment on the Consolidated Balance Sheets.
Amortization Of Software Costs	Amortization of Software Costs. External and internal costs associated with computer software developed for internal use are capitalized. Capitalization of such costs commences upon the completion of the preliminary stage of each project. Once the installed software is ready for its intended use, such capitalized costs are amortized on a straight-line basis generally over a period of five years. CPG amortized $8.7 million in 2015 , $4.3 million in 2014 and $5.0 million in 2013 related to software costs. CPG’s unamortized software balance was $59.8 million and $18.3 million at December 31, 2015 and 2014 , respectively.
Goodwill	Goodwill. CPG has $1,975.5 million in goodwill. All goodwill relates to the excess of cost over the fair value of the net assets acquired in the CEG acquisition on November 1, 2000. Please see Note 9, "Goodwill," in the Notes to Consolidated and Combined Financial Statements for further discussion.
Impairments	Impairments. An impairment loss on long-lived assets shall be recognized only if the carrying amount of a long-lived assets is not recoverable and exceeds its fair value. The test for impairment compares the carrying amount of the long-lived asset to the sum of the undiscounted cash flows expected to result from the use and eventual disposition of the asset. CPG recognized an impairment loss of $2.4 million for the year ended December 31, 2015 and zero for the years ended December 31, 2014 and 2013 .
Revenue Recognition	Revenue Recognition. Revenue is recorded as services are performed. Revenues are billed to customers monthly at rates established through the FERC's cost-based rate-making process or at rates less than those allowed by the FERC. Revenues are recorded on the accrual basis and include estimates for transportation provided but not billed. The demand and commodity charges for transportation of gas under long-term agreements are recognized separately. Demand revenues are recognized monthly over the term of the agreement with the customer regardless of the volume of natural gas transported. Commodity revenues for both firm and interruptible transportation are recognized in the period the transportation services are provided based on volumes of natural gas physically delivered at the agreed upon delivery point. CPG provides shorter term transportation and storage services for which cash is received at inception of the service period resulting in the recording of deferred revenues that are recognized in revenues over the period the services are provided. Storage capacity revenues are recognized monthly over the term of the agreement with the customer regardless of the volume of storage service actually utilized. Injection and withdrawal revenues are recognized in the period when volumes of natural gas are physically injected into or withdrawn from storage. CPG includes the subsidiary CEVCO, which owns the mineral rights to approximately 460,000 acres in the Marcellus and Utica shale areas. CEVCO leases or contributes the mineral rights to producers in return for royalty interest. Royalties from mineral interests are recognized on an accrual basis when earned and realized. Royalty revenue was $26.5 million , $43.8 million and $21.2 million for the years ended December 31, 2015 , 2014 and 2013 , respectively, and is included in "Other revenues" on the Statements of Consolidated and Combined Operations. CPG periodically recognizes gains on the conveyance of mineral interest related to pooling of assets (production rights) in joint undertakings intended to find, develop, or produce oil or gas from a particular property or group of properties. The gains are initially deferred if CPG has a substantial obligation for future performance. As the obligation for future performance is satisfied, the deferred revenue is relieved and the associated gain is recognized. Gains on conveyances amounted to $52.3 million , $34.5 million and $7.3 million for the years ended December 31, 2015 , 2014 and 2013 , respectively, and are included in "Gain on sale of assets and impairment, net" on the Statements of Consolidated and Combined Operations.
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: Year Ended December 31, (in millions) 2015 2014 2013 Predecessor Basic average common shares outstanding 328.5 317.6 317.6 Dilutive potential common shares: Shares restricted under stock plans 0.6 — — Diluted weighted average shares outstanding 329.1 317.6 317.6 Dividends. CPG paid a dividend of $0.125 per share to common stockholders on August 20, 2015 . On August 4, 2015 , CPG declared a dividend of $0.125 per share to common stockholders of record at October 30, 2015 , payable November 20, 2015 . On January 29, 2016 , CPG declared a dividend of $0.12875 per share to common stockholders of record at February 8, 2016 , payable February 19, 2016 .
Estimated Rate Refunds	Estimated Rate Refunds . CPG collects revenue subject to refund pending final determination in rate proceedings. In connection with such revenues, estimated rate refund liabilities are recorded which reflect management’s current judgment of the ultimate outcomes of the proceedings. No provisions are made when, in the opinion of management, the facts and circumstances preclude a reasonable estimate of the outcome.
Accounting For Exchange And Balancing Arrangements Of Natural Gas	Accounting for Exchange and Balancing Arrangements of Natural Gas. CPG enters into balancing and exchange arrangements of natural gas as part of its operations. CPG records a receivable or payable for its respective cumulative gas imbalances. These receivables and payables are recorded as “Exchange gas receivable” or “Exchange gas payable” on CPG’s Consolidated Balance Sheets, as appropriate.
Income Taxes And Investment Tax Credits	Income Taxes and Investment Tax Credits. CPG records income taxes to recognize full inter period tax allocations. Under the liability method, deferred income taxes are provided for the tax consequences of temporary differences by applying enacted statutory tax rates applicable to future years to differences between the financial statement carrying amounts and the tax basis of existing assets and liabilities. To the extent certain deferred income taxes of CPG are recoverable or payable through future rates, regulatory assets and liabilities have been established. In prior years, and for the period ending July 1, 2015, CPG joined in the filing of consolidated federal and state income tax returns with NiSource. CPG was a party to an agreement (“Tax Allocation Agreement”) that provides for the allocation of consolidated tax liabilities. The Tax Allocation Agreement generally provides that each party is allocated an amount of tax similar to that which would be owed had the party been separately subject to tax. In addition, the Tax Allocation Agreement provides that tax benefits associated with NiSource parent’s tax losses, excluding tax benefits from interest expense on acquisition debt, are allocated to and reduce the income tax liability of all NiSource subsidiaries having a positive separate company tax liability in a particular tax year. The amounts of such tax benefits allocated to CPG that were recorded in equity in 2015 , 2014 and 2013 were $5.8 million , $1.3 million and $5.3 million , respectively.
Environmental Expenditures	Environmental Expenditures. CPG accrues for costs associated with environmental remediation obligations when the incurrence of such costs is probable and the amounts can be reasonably estimated, regardless of when the expenditures are actually made. The undiscounted estimated future expenditures are based on currently enacted laws and regulations, existing technology and estimated site-specific costs where assumptions may be made about the nature and extent of site contamination, the extent of cleanup efforts, costs of alternative cleanup methods and other variables. The liability is adjusted as further information is discovered or circumstances change. The reserves for estimated environmental expenditures are recorded on the Consolidated Balance Sheets in “Other Accruals” for short-term portions of these liabilities and “Other noncurrent liabilities” for the respective long-term portions of these liabilities. CPG establishes regulatory assets on the Consolidated Balance Sheets to the extent that future recovery of environmental remediation costs is probable through the regulatory process. Please see Note 19, "Other Commitments and Contingencies" in the Notes to Consolidated and Combined Financial Statements for further discussion.
Accounting For Investments	Accounting for Investments. CPG accounts for its ownership interests in Millennium Pipeline using the equity method of accounting. Columbia Gas Transmission owns a 47.5% interest in Millennium Pipeline. The equity method of accounting is applied for investments in unconsolidated companies where CPG (or a subsidiary) owns 20 to 50 percent of the voting rights and can exercise significant influence. CPG owns a 50.0% interest in Hardy Storage for the periods presented. CPG reflects the investment in Hardy Storage as an equity method investment. Columbia Midstream entered into a 50:50 joint venture in 2012 with Hilcorp to construct Pennant, a new wet natural gas gathering infrastructure and NGL processing facilities to support natural gas production in the Utica Shale region of northeastern Ohio and western Pennsylvania. During the third quarter of 2015, an additional member, an affiliate of Williams Partners, joined the Pennant joint venture. Williams Partners' initial ownership investment in Pennant is 5.00% , and by funding specified investment amounts for future growth projects, Williams Partners can invest directly in the growth of Pennant. Such funding will potentially increase Williams Partners' ownership in Pennant up to 33.33% over a defined investment period. As a result of the buy-in, Columbia Midstream received $12.7 million in cash and recorded a gain of $2.9 million , and its ownership interest in Pennant decreased from 50.0% to 47.5% . CPG accounts for the joint venture under the equity method of accounting.
Natural Gas and Oil Properties	Natural Gas and Oil Properties. CEVCO participates as a working interest partner in the development of a broader acreage dedication. The working interest allows CEVCO to invest in the drilling operations of the partnership in addition to a royalty interest in well production. Please see Note 1K, “Revenue Recognition,” in the Notes to Consolidated and Combined Financial Statements for further discussion regarding the royalty revenue. CEVCO uses the successful efforts method of accounting for natural gas and oil producing activities for their portion of drilling activities. Capitalized well costs are depleted based on the units of production method. CEVCO’s portion of unproved property investment is periodically evaluated for impairment. The majority of these costs generally relate to CEVCO’s portion of the working interest. The costs are capitalized and evaluated (at least quarterly) as to recoverability, based on changes brought about by economic factors and potential shifts in business strategy employed by management. Impairment of individually significant unproved property is assessed on a field-by-field basis considering a combination of time, geologic and engineering factors. The following table reflects the changes in capitalized exploratory well costs for the years ended December 31, 2015 and 2014 : (in millions) 2015 2014 Beginning Balance $ 14.9 $ 1.9 Additions pending the determination of proved reserves 1.3 20.1 Reclassifications of proved properties (14.5 ) (7.1 ) Ending Balance $ 1.7 $ 14.9 As of December 31, 2015 , there was $0.3 million of capitalized exploratory well costs that have been capitalized for more than one year relating to one project initiated in 2013 .

Nature Of Operations And Summ37

Nature Of Operations And Summary Of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of AFUDC Debt and Equity Rates	2015 2014 2013 Debt Equity Debt Equity Debt Equity Predecessor Columbia Gas Transmission 1.8 % 6.3 % 0.9 % 3.0 % 2.5 % 3.2 % Columbia Gulf 2.9 % 6.3 % 2.1 % 9.4 % 2.5 % 3.2 %
Computation Of Diluted Average Common Shares	Year Ended December 31, (in millions) 2015 2014 2013 Predecessor Basic average common shares outstanding 328.5 317.6 317.6 Dilutive potential common shares: Shares restricted under stock plans 0.6 — — Diluted weighted average shares outstanding 329.1 317.6 317.6
Capitalized Exploratory Well Costs, Roll Forward	(in millions) 2015 2014 Beginning Balance $ 14.9 $ 1.9 Additions pending the determination of proved reserves 1.3 20.1 Reclassifications of proved properties (14.5 ) (7.1 ) Ending Balance $ 1.7 $ 14.9

CPPL Initial Public Offering (T

CPPL Initial Public Offering (Tables)	12 Months Ended
	Dec. 31, 2015
Initial Public Offering [Abstract]
Change From Net Income Attributable to CPG and Transfers to Noncontrolling Interest	Year Ended (in millions) 2015 Net income attributable to CPG $ 267.2 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 $ 494.3

Transactions with Affiliates (T

Transactions with Affiliates (Tables)	12 Months Ended
	Dec. 31, 2015
Related Party Transactions [Abstract]
Schedule of Transactions With Affiliates	Statement of Operations Year Ended (in millions) 2015 2014 2013 Predecessor Transportation revenues $ 47.5 $ 95.7 $ 94.1 Storage revenues 26.2 53.2 53.6 Other revenues 0.2 0.3 0.3 Operation and maintenance expense 52.9 123.2 118.6 Interest expense 29.3 62.0 37.9 Interest income 2.5 0.7 0.7 Balance Sheet (in millions) December 31, 2015 December 31, 2014 Accounts receivable $ — $ 180.0 Current portion of long term debt- affiliated — 115.9 Short-term borrowings — 252.5 Accounts payable — 53.6 Long-term debt — 1,472.8
Schedule of Related Party Transactions, Long-Term Debt	Origination Date Interest Rate Maturity Date December 31, 2015 December 31, 2014 (in millions) November 28, 2005 (1) 5.41 % November 30, 2015 $ — $ 115.9 November 28, 2005 5.45 % November 28, 2016 — 45.3 November 28, 2005 5.92 % November 28, 2025 — 133.5 November 28, 2012 4.63 % November 28, 2032 — 45.0 November 28, 2012 4.94 % November 30, 2037 — 95.0 December 19, 2012 5.16 % December 21, 2037 — 55.0 November 28, 2012 5.26 % November 28, 2042 — 170.0 December 19, 2012 5.49 % December 18, 2042 — 95.0 December 9, 2013 4.75 % December 31, 2016 — 834.0 Total Long-term Debt $ — $ 1,588.7 (1) The debt balance for the note originating on November 28, 2005 and maturing on November 30, 2015 is included in "Current portion of long-term debt-affiliated" on the Consolidated Balance Sheets as of December 31, 2014.

Short-Term Borrowings (Tables)

Short-Term Borrowings (Tables)	12 Months Ended
	Dec. 31, 2015
Short-term Debt [Abstract]
Schedule Of Short-Term Borrowings	At December 31, (in millions) 2015 2014 Commercial paper borrowings $ — $ — CPG credit facility borrowings — — CPPL credit facility borrowings, weighted average interest rate of 1.28% at December 31, 2015 15.0 — Total Short-Term Borrowings $ 15.0 $ —

Long-Term Debt (Tables)

Long-Term Debt (Tables)	12 Months Ended
	Dec. 31, 2015
Long-term Debt, Current and Noncurrent [Abstract]
Schedule Of Outstanding Long Term Debt Maturities	Year Ending December 31, (in millions) 2016 $ — 2017 — 2018 500.0 2019 — 2020 750.0 After 1,500.0 Total (1) $ 2,750.0 (1) This amount excludes unamortized discount of $3.8 million . The unamortized discount applicable to the Notes is being amortized over the weighted average life of the Notes.

Property, Plant And Equipment (

Property, Plant And Equipment (Tables)	12 Months Ended
	Dec. 31, 2015
Property, Plant and Equipment [Abstract]
Schedule Of Property, Plant And Equipment	At December 31, (in millions) 2015 2014 Property, plant and equipment Pipeline and other transmission assets $ 6,160.4 $ 5,333.0 Storage facilities 1,370.1 1,326.5 Gas stored base gas 299.5 299.5 Gathering and processing facilities 370.2 263.3 Construction work in process 487.6 454.2 General plant, software, and other assets 364.5 258.9 Property, plant and equipment 9,052.3 7,935.4 Accumulated depreciation and amortization (2,988.6 ) (2,976.8 ) Net property, plant and equipment $ 6,063.7 $ 4,958.6
Schedule of Depreciation Rates	Year Ended December 31, 2015 2014 2013 Predecessor Depreciation rates Pipeline and other transmission assets 1.00% - 2.50% 1.00% - 2.50% 1.00% - 2.50% Storage facilities 2.19% - 3.00% 2.19% - 3.30% 2.19% - 3.50% Gathering and processing facilities 1.67% - 2.50% 1.67% - 2.50% 1.67% - 2.50% General plant, software, and other assets 1.00% - 21.00% 1.00% - 10.00% 1.00% - 10.00%

Asset Retirement Obligations (T

Asset Retirement Obligations (Tables)	12 Months Ended
	Dec. 31, 2015
Asset Retirement Obligation [Abstract]
Changes In Liability For Asset Retirement Obligations	(in millions) 2015 2014 Beginning Balance $ 23.2 $ 26.3 Accretion expense 1.2 1.5 Additions 4.1 2.2 Settlements — (6.6 ) Change in estimated cash flows (2.8 ) (0.2 ) Ending Balance $ 25.7 $ 23.2

Regulatory Matters (Tables)

Regulatory Matters (Tables)	12 Months Ended
	Dec. 31, 2015
Regulatory Assets and Liabilities Disclosure [Abstract]
Regulatory Assets	At December 31, (in millions) 2015 2014 Assets Unrecognized pension benefit and other postretirement benefit costs $ 135.2 $ 120.9 Other postretirement costs 9.0 10.8 Deferred taxes on AFUDC equity 35.4 21.8 Other 3.1 4.5 Total Regulatory Assets $ 182.7 $ 158.0
Regulatory Liabilities	At December 31, (in millions) 2015 2014 Liabilities Cost of removal $ 154.7 $ 157.6 Regulatory effects of accounting for income taxes 10.6 10.9 Unrecognized pension benefit and other postretirement benefit costs 0.7 8.3 Other postretirement costs 155.6 117.3 Other 1.2 2.9 Total Regulatory Liabilities $ 322.8 $ 297.0

Equity Method Investments (Tabl

Equity Method Investments (Tables)	12 Months Ended
	Dec. 31, 2015
Variable Interest Entities And Equity Investments [Abstract]
Equity Method Investments Schedule of Ownership Percentage	The following is a list of CPG's equity method investments at December 31, 2015 : Investee Type of Investment % of Voting Power or Interest Held Hardy Storage Company, LLC LLC Membership 50.0 % Pennant Midstream, LLC LLC Membership 47.5 % Millennium Pipeline Company, L.L.C. LLC Membership 47.5 %
Schedule Of Equity Method Investments	Year Ended December 31, (in millions) 2015 2014 2013 Predecessor Millennium Pipeline Statement of Income Data: Net Revenues $ 206.3 $ 190.5 $ 157.8 Operating Income 136.1 128.8 101.3 Net Income 98.0 89.6 63.0 Balance Sheet Data: Current Assets 35.7 32.1 38.3 Noncurrent Assets 987.1 1,016.3 1,033.8 Current Liabilities 44.4 42.6 58.8 Noncurrent Liabilities 535.8 568.3 599.7 Total Members’ Equity 442.6 437.5 413.6 Contribution/Distribution Data: (1) Contributions to Millennium Pipeline 1.4 2.6 16.6 Distribution of earnings from Millennium Pipeline 47.5 35.6 29.0 Hardy Storage Statement of Income Data: Net Revenues $ 23.4 $ 23.6 $ 24.4 Operating Income 15.3 16.1 16.5 Net Income 10.3 10.6 10.6 Balance Sheet Data: Current Assets 12.1 12.0 12.5 Noncurrent Assets 155.5 157.4 160.2 Current Liabilities 19.3 17.1 18.3 Noncurrent Liabilities 68.5 77.4 85.7 Total Members’ Equity 79.8 74.9 68.7 Contribution/Distribution Data: (1) Contributions to Hardy Storage — — — Distribution of earnings from Hardy Storage 2.6 2.2 3.1 Pennant Statement of Income Data: Net Revenues $ 34.6 $ 8.5 $ 2.0 Operating Income (Loss) 17.8 (2.4 ) 1.3 Net Income (Loss) 17.8 (2.4 ) 1.3 Balance Sheet Data: Current Assets 11.0 23.7 34.1 Noncurrent Assets 389.6 380.0 231.9 Current Liabilities 8.4 8.6 11.4 Total Members’ Equity 392.2 395.1 254.6 Contribution/Distribution Data: (1) Contributions to Pennant — 66.6 108.9 Distribution of earnings from Pennant 7.1 — — Return of capital from Pennant 16.0 — — (1) Contribution and distribution data represents CPG's portion based on CPG's ownership percentage of each investment.

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Schedule Of Components Of Income Tax Expense	Year Ended December 31, (in millions) 2015 2014 2013 Predecessor Income Taxes Current Federal $ 12.1 $ 19.5 $ (15.5 ) State 9.1 7.6 (11.9 ) Total Current 21.2 27.1 (27.4 ) Deferred Federal 120.2 119.2 157.4 State 11.6 23.5 16.6 Total Deferred 131.8 142.7 174.0 Deferred Investment Credits — (0.1 ) (0.1 ) Total Income Taxes $ 153.0 $ 169.7 $ 146.5
Schedule Of Reasons Behind Differences In Computation Of Total Income Taxes	Year Ended December 31, (in millions) 2015 2014 2013 Predecessor Book income from Continuing Operations before income taxes $ 460.5 $ 438.4 $ 418.2 Tax expense at statutory federal income tax rate 161.2 35.0 % 153.5 35.0 % 146.4 35.0 % Increases (reductions) in taxes resulting from: State income taxes, net of federal income tax benefit 13.4 2.9 20.3 4.6 3.0 0.7 Noncontrolling interest (14.0 ) (3.0 ) — — — — AFUDC-Equity (9.2 ) (2.0 ) (3.7 ) (0.8 ) (2.4 ) (0.6 ) Other, net 1.6 0.3 (0.4 ) (0.1 ) (0.5 ) (0.1 ) Total Income Taxes $ 153.0 33.2 % $ 169.7 38.7 % $ 146.5 35.0 %
Schedule Of Principal Components Of Net Deferred Tax Liability	At December 31, (in millions) 2015 2014 Deferred tax liabilities Accelerated depreciation and other property differences $ 1,429.2 $ 1,235.2 Pension and other postretirement/postemployment benefits 29.9 27.7 Other regulatory assets 71.8 62.8 Equity method investments 124.3 99.2 Total Deferred Tax Liabilities 1,655.2 1,424.9 Deferred tax assets Other regulatory liabilities (126.8 ) (116.7 ) Net operating loss carryforward (141.4 ) (70.3 ) Other (38.9 ) (42.2 ) Total Deferred Tax Assets (307.1 ) (229.2 ) Net Deferred Tax Liabilities 1,348.1 1,195.7 Less: Deferred income taxes related to current assets and liabilities — (60.0 ) Non-Current Deferred Tax Liability $ 1,348.1 $ 1,255.7

Pension And Other Postretirem47

Pension And Other Postretirement Benefits (Tables)	12 Months Ended
	Dec. 31, 2015
Pension and Other Postretirement Benefit Expense [Abstract]
Schedule Of Allocation of Plan Assets	Defined Benefit Pension Plan Postretirement Benefit Plan Asset Category Minimum Maximum Minimum Maximum Domestic Equities 25% 45% 35% 55% International Equities 15% 25% 15% 25% Fixed Income 23% 37% 20% 50% Real Estate/Private Equity/Hedge Funds 0% 15% 0% 0% Short-Term Investments 0% 10% 0% 10% Pension Plan and Postretirement Plan Asset Mix at December 31, 2015 and December 31, 2014 : December 31, 2015 Defined Benefit Postretirement Asset Class Asset Value % of Total Assets Asset Value % of Total Assets (in millions) (in millions) Domestic Equities $ 141.0 39.4 % $ 101.6 44.4 % International Equities 62.5 17.5 % 42.8 18.8 % Fixed Income 123.3 34.4 % 76.6 33.6 % Cash/Other 31.0 8.7 % 7.2 3.2 % Total $ 357.8 100.0 % $ 228.2 100.0 % December 31, 2014 Defined Benefit Postretirement Asset Class Asset Value % of Total Assets Asset Value % of Total Assets (in millions) (in millions) Domestic Equities $ 144.2 41.1 % $ 105.7 47.2 % International Equities 63.3 18.1 % 41.2 18.4 % Fixed Income 120.9 34.4 % 76.3 34.1 % Real Estate/Private Equity/Hedge Funds 17.7 5.0 % — — % Cash/Other 4.9 1.4 % 0.6 0.3 % Total $ 351.0 100.0 % $ 223.8 100.0 %
Schedule Of Fair Value and Changes In The Fair Value Of The Plan Assets	Fair Value Measurements (in millions) December 31, Quoted Prices in Active Significant Other Significant Pension plan assets Cash $ 0.9 $ 0.9 $ — $ — Equity securities International equities 6.6 6.6 — — Fixed income securities Government 8.5 — 8.5 — Corporate 13.0 — 13.0 — Commingled funds Short-term money markets 31.1 — 31.1 — U.S. equities 141.0 — 141.0 — International equities 55.6 — 55.6 — Fixed income 100.9 — 100.9 — Pension plan assets subtotal 357.6 7.5 350.1 — Other postretirement benefit plan assets Commingled funds Short-term money markets 7.3 — 7.3 — U.S. equities 13.9 — 13.9 — Mutual funds U.S. equities 87.7 87.7 — — International equities 42.8 42.8 — — Fixed income 76.5 76.5 — — Other postretirement benefit plan assets subtotal 228.2 207.0 21.2 — Due to brokers, net (1) (0.4 ) Accrued investment income/dividends 0.6 Total pension and other postretirement benefit plan assets $ 586.0 $ 214.5 $ 371.3 $ — (1) This class represents pending trades with brokers. The table below sets forth a summary of changes in the fair value of the Plan’s Level 3 assets for the year ended December 31, 2015 : (in millions) Balance at January 1, 2015 Total gains or losses (unrealized / realized) Purchases (Sales) Transfers into/(out of) level 3 Separation Allocation (1) Balance at December 31, 2015 Fixed income securities Other fixed income $ 0.1 $ — $ — $ — $ — $ (0.1 ) $ — Private equity limited partnerships U.S. multi-strategy 8.5 — — — — (8.5 ) — International multi-strategy 5.3 — — — — (5.3 ) — Distressed opportunities 1.1 — — — — (1.1 ) — Real estate 2.6 — — — — (2.6 ) — Total $ 17.6 $ — $ — $ — $ — (17.6 ) $ — (1) Level 3 assets were not contributed to the CPG Plans upon Separation from NiSource and no subsequent investments were made in Level 3 assets post Separation. Fair Value Measurements at December 31, 2014 : Fair Value Measurements (in millions) December 31, Quoted Prices in Active Significant Other Significant Pension plan assets Cash $ 2.6 $ 2.6 $ — $ — Equity securities U.S. equities 0.1 0.1 — — International equities 20.3 20.2 0.1 — Fixed income securities Government 17.8 15.7 2.1 — Corporate 38.7 — 38.7 — Mortgages/Asset backed securities 0.4 — 0.4 — Other fixed income 0.1 — — 0.1 Commingled funds Short-term money markets 4.9 — 4.9 — U.S. equities 144.2 — 144.2 — International equities 42.1 — 42.1 — Fixed income 61.6 — 61.6 — Private equity limited partnerships U.S. multi-strategy (1) 8.5 — — 8.5 International multi-strategy (2) 5.3 — — 5.3 Distressed opportunities 1.1 — — 1.1 Real Estate 2.6 — — 2.6 Pension plan assets subtotal 350.3 38.6 294.1 17.6 Other postretirement benefit plan assets Commingled funds Short-term money markets 0.8 — 0.8 — U.S. equities 14.3 — 14.3 — Mutual funds U.S. equities 91.3 91.3 — — International equities 41.2 41.2 — — Fixed income 76.2 76.2 — — Other postretirement benefit plan assets subtotal 223.8 208.7 15.1 — Due to brokers, net (3) (0.1 ) Accrued investment income/dividends 0.1 Net receivables 0.7 Total pension and other postretirement benefit plan assets $ 574.8 $ 247.3 $ 309.2 $ 17.6 (1) This class includes limited partnerships/fund of funds that invest in a diverse portfolio of private equity strategies, including buy-outs, venture capital, growth capital, special situations and secondary markets, primarily in the United States. (2) This class includes limited partnerships/fund of funds that invest in a diverse portfolio of private equity strategies, including buy-outs, venture capital, growth capital, special situations and secondary markets, primarily outside the United States. (3) This class represents pending trades with brokers. The table below sets forth a summary of changes in the fair value of the Plan’s Level 3 assets for the year ended December 31, 2014 : (in millions) Balance at January 1, 2014 Total gains or losses (unrealized / realized) Purchases (Sales) Transfers into/(out of) level 3 Balance at December 31, 2014 Fixed income securities Other fixed income $ — $ — $ 0.1 $ — $ — $ 0.1 Private equity limited partnerships U.S. multi-strategy 8.7 0.4 0.4 (1.0 ) — 8.5 International multi-strategy 5.8 (0.1 ) 0.1 (0.5 ) — 5.3 Distress opportunities 1.4 0.1 — (0.4 ) — 1.1 Real estate 3.0 0.3 — (0.7 ) — 2.6 Total $ 18.9 $ 0.7 $ 0.6 $ (2.6 ) $ — $ 17.6
Schedule Of Reconciliation Of The Plan Funded Status	Pension Benefits Other Postretirement Benefits (in millions) 2015 2014 2015 2014 Change in projected benefit obligation (1) Benefit obligation at beginning of year $ 397.6 $ 376.7 $ 124.2 $ 120.9 Service cost 5.9 4.8 1.0 1.1 Interest cost 15.0 15.7 4.7 5.2 Plan participants’ contributions — — 2.3 3.0 Actuarial loss (gain) (6.9 ) 22.7 (12.4 ) 5.7 Benefits paid (29.7 ) (22.3 ) (9.8 ) (12.4 ) Estimated benefits paid by incurred subsidy — — 0.3 0.7 Transfer of participant balances from NiSource plans (2) 22.6 — 1.8 — Projected benefit obligation at end of year $ 404.5 $ 397.6 $ 112.1 $ 124.2 Change in plan assets Fair value of plan assets at beginning of year $ 351.0 $ 344.5 $ 223.8 $ 209.7 Actual return on plan assets 1.2 21.1 (2.5 ) 11.6 Employer contributions 20.0 7.7 13.5 11.9 Plan participants’ contributions — — 2.3 3.0 Benefits paid (29.7 ) (22.3 ) (9.8 ) (12.4 ) Transfer of participant balances from NiSource plans (2) 15.3 — 0.9 — Fair value of plan assets at end of year $ 357.8 $ 351.0 $ 228.2 $ 223.8 Funded status at end of year $ (46.7 ) $ (46.6 ) $ 116.1 $ 99.6 Amounts recognized in the balance sheet consist of: Noncurrent assets $ — $ — $ 116.1 $ 113.1 Current liabilities (0.8 ) — — — Noncurrent liabilities (45.9 ) (46.6 ) — (13.5 ) Net amount recognized at end of year (3) $ (46.7 ) $ (46.6 ) $ 116.1 $ 99.6 Amounts recognized in AOCI or regulatory assets/liabilities (4) Unrecognized prior service credit $ (3.7 ) $ (4.7 ) $ (2.0 ) $ (2.6 ) Unrecognized actuarial loss (gain) 164.5 148.7 (3.9 ) (12.5 ) Total recognized AOCI or regulatory assets/liabilities $ 160.8 $ 144.0 $ (5.9 ) $ (15.1 ) (1) The change in benefit obligation for Pension Benefits represents the change in Projected Benefit Obligation while the change in benefit obligation for Other Postretirement Benefits represents the change in Accumulated Postretirement Benefit Obligation. (2) Reflects the transfer of additional pension and OPEB plan participants to CPGSC upon Separation from NiSource that were determined in the current year. (3) CPG recognizes in its Consolidated Balance Sheets the underfunded and overfunded status of its various defined benefit postretirement plans, measured as the difference between the fair value of the plan assets and the benefit obligation. (4) CPG determined that the future recovery of pension and other postretirement benefits costs is probable. CPG recorded regulatory assets and liabilities of $135.2 million and $0.7 million , respectively, as of December 31, 2015 , and $120.9 million and $8.3 million , respectively, as of December 31, 2014 that would otherwise have been recorded to accumulated other comprehensive loss.
Schedule Of Significant Actuarial Assumptions In Determining Funded Status Plan	Pension Benefits Other Postretirement Benefits 2015 2014 2015 2014 Weighted-average assumptions to Determine Benefit Obligation Discount Rate 4.05 % 3.64 % 4.29 % 3.96 % Rate of Compensation Increases 4.00 % 4.00 % Health Care Trend Rates Trend for Next Year 8.39 % 6.90 % Ultimate Trend 4.50 % 4.50 % Year Ultimate Trend Reached 2022 2021
Schedule Of One-Percentage-Point Change In Assumed Health Care Cost Trend Rates	(in millions) 1% point increase 1% point decrease Effect on service and interest components of net periodic cost $ 0.1 $ (0.1 ) Effect on accumulated postretirement benefit obligation 3.1 (2.8 )
Schedule Of Expected Payments To Participants In Pension Plan	(in millions) Pension Benefits Other Federal Year(s) 2016 $ 34.9 $ 8.2 $ 0.6 2017 33.9 8.0 0.6 2018 35.1 8.0 0.6 2019 35.8 7.9 0.6 2020 37.1 7.9 0.5 2021-2025 175.3 37.4 1.7
Components Of The Plans' Net Periodic Benefits Cost	Pension Benefits Other Postretirement Benefits (in millions) 2015 2014 2013 2015 2014 2013 Predecessor Predecessor Components of Net Periodic Benefit Cost (Income) Service cost $ 5.9 $ 4.8 $ 4.9 $ 1.0 $ 1.1 $ 1.5 Interest cost 15.0 15.7 14.6 4.7 4.6 5.4 Expected return on assets (28.2 ) (27.3 ) (25.5 ) (18.1 ) (16.6 ) (13.8 ) Amortization of prior service (credit) cost (1.1 ) (1.1 ) (1.1 ) (0.3 ) 0.1 0.1 Recognized actuarial loss (gain) 9.9 7.5 12.3 (0.3 ) — 1.0 Net Periodic Benefit Cost (Income) 1.5 (0.4 ) 5.2 (13.0 ) (10.8 ) (5.8 ) Settlement loss — — 13.8 — — — Total Net Periodic Benefit Cost (Income) $ 1.5 $ (0.4 ) $ 19.0 $ (13.0 ) $ (10.8 ) $ (5.8 )
Schedule Of Key Assumptions That Were Used To Calculate The Net Periodic Benefits Cost	Pension Benefits Other Postretirement Benefits 2015 2014 2013 2015 2014 2013 Predecessor Predecessor Weighted-average Assumptions to Determine Net Periodic Benefit Cost Discount Rate 3.84 % 4.34 % 3.36 % 4.10 % 4.76 % 3.92 % Expected Long-Term Rate of Return on Plan Assets 8.20 % 8.30 % 8.30 % 8.05 % 8.14 % 8.17 % Rate of Compensation Increases 4.00 % 4.00 % 4.00 %
Schedule Of Changes In Plan Assets And Projected Benefit Obligations Recognized In Other Comprehensive Income	Pension Benefits Other Postretirement Benefits (in millions) 2015 2014 2015 2014 Other changes in plan assets and projected benefit obligations recognized in other comprehensive income or regulatory assets or liabilities Net actuarial loss $ 25.6 $ 28.9 $ 8.6 $ 11.8 Less: amortization of prior service (credit) cost 1.1 1.1 0.3 (0.1 ) Less: amortization of net actuarial (gain) loss (9.9 ) (7.5 ) 0.3 — Total recognized in other comprehensive income or regulatory assets or liabilities $ 16.8 $ 22.5 $ 9.2 $ 11.7 Amount recognized in net periodic benefit cost and other comprehensive income or regulatory assets or liabilities $ 18.3 $ 22.1 $ (3.8 ) $ 0.9

Fair Value (Tables)

Fair Value (Tables)	12 Months Ended
	Dec. 31, 2015
Fair Value Disclosures [Abstract]
Carrying Amount And Estimated Fair Values Of Financial Instruments	At December 31, (in millions) Carrying Amount 2015 Estimated Fair Value 2015 Carrying Amount 2014 Estimated Fair Value 2014 Current portion of long-term debt - affiliated $ — $ — $ 115.9 $ 120.0 Long-term debt 2,746.2 2,592.1 — — Long-term debt - affiliated — — 1,472.8 1,550.4

Share-Based Compensation (Table

Share-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2015
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Schedule Of Transactions Of Share Based Compensation Other Than Stock Options	Restricted Stock Units Weighted Average Grant Date Fair Value Nonvested at December 31, 2014 230,187 $ 20.27 Performance shares converted to restricted shares at Separation 1,460,401 15.66 Granted 580,267 26.29 Forfeited (495 ) 28.25 Vested (1,568 ) 18.24 Nonvested and Expected to Vest at December 31, 2015 2,268,792 $ 18.85
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Schedule Of Transactions Of Share Based Compensation Other Than Stock Options	Contingent Awards Weighted Average Grant Date Fair Value Nonvested at December 31, 2014 1,460,401 $ 15.66 Performance shares converted to restricted shares at Separation (1,460,401 ) 15.66 Granted 161,504 28.16 Forfeited — — Vested — — Nonvested and Expected to Vest at December 31, 2015 161,504 $ 28.16

Other Commitments And Conting50

Other Commitments And Contingencies (Tables)	12 Months Ended
	Dec. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Schedule of Guarantor Obligations	(in millions) Total 2016 2017 2018 2019 2020 After Letters of credit $ 18.1 $ 18.1 $ — $ — $ — $ — $ — Other guarantees 45.7 0.6 2.0 — — — 43.1 Total commercial commitments $ 63.8 $ 18.7 $ 2.0 $ — $ — $ — $ 43.1
Future Minimum Lease Payments Required Under Operating And Capital Leases	(in millions) Operating Leases (1) 2016 $ 5.4 2017 6.7 2018 6.2 2019 5.5 2020 5.4 After 24.7 Total future minimum payments $ 53.9 (1) Operating lease expense includes amounts for fleet leases and storage well leases that can be renewed beyond the initial lease term, but the anticipated payments associated with the renewals do not meet the definition of expected minimum lease payments and, therefore, are not included above.
Estimated Aggregate Amounts Of Minimum Fixed Payments On Purchase And Service Obligations	(in millions) Pipeline Service Agreements IBM Service Agreement 2016 $ 51.5 $ 38.6 2017 49.5 33.0 2018 42.0 31.7 2019 25.4 31.0 2020 24.2 31.0 After 66.8 — Total future minimum payments $ 259.4 $ 165.3

Accumulated Other Comprehensi51

Accumulated Other Comprehensive Loss (Tables)	12 Months Ended
	Dec. 31, 2015
Components of Accumulated Other Comprehensive Income (Loss) [Abstract]
Schedule of Accumulated Other Comprehensive Income (Loss)	(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, 2013 - Predecessor $ (18.7 ) $ (16.4 ) $ (35.1 ) Other comprehensive income before reclassifications — 6.5 6.5 Amounts reclassified from accumulated other comprehensive income 1.1 1.7 2.8 Net current-period other comprehensive income 1.1 8.2 9.3 Balance as of December 31, 2013 - Predecessor $ (17.6 ) $ (8.2 ) $ (25.8 ) Other comprehensive income before reclassifications — (9.3 ) (9.3 ) Amounts reclassified from accumulated other comprehensive income 1.0 (0.4 ) 0.6 Net current-period other comprehensive income 1.0 (9.7 ) (8.7 ) Balance as of December 31, 2014 $ (16.6 ) $ (17.9 ) $ (34.5 ) Other comprehensive income before reclassifications (0.9 ) 5.0 4.1 Amounts reclassified from accumulated other comprehensive income 1.1 0.2 1.3 Net current-period other comprehensive income 0.2 5.2 5.4 Allocation of accumulated other comprehensive loss to noncontrolling interest 2.1 — 2.1 Balance as of December 31, 2015 $ (14.3 ) $ (12.7 ) $ (27.0 ) (1) All amounts are net of tax. Amounts in parentheses indicate debits.

Other, Net (Tables)

Other, Net (Tables)	12 Months Ended
	Dec. 31, 2015
Other Nonoperating Income (Expense) [Abstract]
Schedule Of Other, Net	Year Ended December 31, (in millions) 2015 2014 2013 Predecessor AFUDC Equity $ 28.3 $ 11.0 $ 6.8 Miscellaneous (1) 1.0 (2.2 ) 11.1 Total Other, net $ 29.3 $ 8.8 $ 17.9 (1) Miscellaneous primarily consists of a gain from insurance proceeds in 2013.

Interest Expense (Tables)

Interest Expense (Tables)	12 Months Ended
	Dec. 31, 2015
Interest Expense [Abstract]
Schedule Of Interest Expense	Year Ended December 31, (in millions) 2015 2014 2013 Predecessor Interest on long-term debt $ 67.5 $ — $ — Interest on short-term borrowings (1) 1.4 — — Debt discount/cost amortization 3.1 — — Allowance for funds used during construction (6.8 ) — — Other 2.4 — — Total Interest Expense (2) $ 67.6 $ — $ — (1) Refer to Note 5, "Short-Term Borrowings" for additional information. (2) Refer to Note 4, "Transactions with Affiliates" for a discussion of interest expense-affiliated for the year ended December 31, 2014 and 2013 .

Supplemental Cash Flow Inform54

Supplemental Cash Flow Information (Tables)	12 Months Ended
	Dec. 31, 2015
Supplemental Cash Flow Information [Abstract]
Schedule of Cash Flow, Supplemental Disclosures	Year Ended December 31, (in millions) 2015 2014 2013 Predecessor Supplemental Disclosures of Cash Flow Information Non-cash transactions: Capital expenditures included in current liabilities (1) $ 128.4 $ 78.5 $ 53.1 Schedule of interest and income taxes paid: Cash paid for interest, net of interest capitalized amounts $ 96.9 $ 53.6 $ 38.4 Cash paid for income taxes (2) 32.3 21.2 15.3 (1) Capital expenditures included in current liabilities is comprised of "Accrued capital expenditures" and certain other amounts included within "Accounts payable" on the Consolidated Balance Sheets. (2) Cash paid for income taxes for the year ended December 31, 2015 includes $20.9 million paid to NiSource under the Tax Allocation Agreement.

Concentration of Credit Risk (T

Concentration of Credit Risk (Tables)	12 Months Ended
	Dec. 31, 2015
Risks and Uncertainties [Abstract]
Schedules of Concentration of Risk, by Risk Factor	Year Ended December 31, 2015 2014 2013 (in millions) Total Operating Revenues Percentage of Total Operating Revenues Total Operating Revenues Percentage of Total Operating Revenues Total Operating Revenues Percentage of Total Operating Revenues Predecessor Columbia Gas of Ohio (1) $ 167.3 12.5 % $ 168.5 12.5 % $ 167.5 14.2 % (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 agreements with third parties which ultimately can decrease the net revenue amount CPG receives from Columbia Gas of Ohio in any given period.

Quarterly Financial Data (Una56

Quarterly Financial Data (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2015
Quarterly Financial Data [Abstract]
Schedule Of Quarterly Financial Data	(in millions, except per unit data) First Quarter Second Quarter Third Quarter Fourth Quarter 2015 Total Operating Revenues $ 340.0 $ 316.1 $ 320.9 $ 357.9 Operating Income 162.7 107.3 135.9 122.2 Income from Continuing Operations 97.1 60.1 74.9 75.4 Results from Discontinued Operations - net of taxes — (0.3 ) (0.1 ) — Net Income attributable to CPG 90.0 50.8 63.0 63.4 Basic Earnings Per Share Continuing Operations 0.28 0.16 0.20 0.19 Discontinued Operations — — — — Basic Earnings Per Share $ 0.28 $ 0.16 $ 0.20 $ 0.19 Diluted Earnings Per Share Continuing Operations 0.28 0.16 0.20 0.19 Discontinued Operations — — — — Diluted Earnings Per Share $ 0.28 $ 0.16 $ 0.20 $ 0.19 2014 Total Operating Revenues $ 345.8 $ 343.5 $ 318.0 $ 340.7 Operating Income 159.1 103.9 94.5 134.1 Income from Continuing Operations 93.0 59.4 53.7 62.6 Results from Discontinued Operations - net of taxes (0.2 ) (0.3 ) (0.1 ) — Net Income attributable to CPG 92.8 59.1 53.6 62.6 Basic Earnings Per Share Continuing Operations 0.29 0.19 0.17 0.20 Discontinued Operations — — — — Basic Earnings Per Share $ 0.29 $ 0.19 $ 0.17 $ 0.20 Diluted Earnings Per Share Continuing Operations 0.29 0.19 0.17 0.20 Discontinued Operations — — — — Diluted Earnings Per Share $ 0.29 $ 0.19 $ 0.17 $ 0.20

Nature Of Operations And Summ57

Nature Of Operations And Summary Of Significant Accounting Policies (Narrative) (Details) $ / shares in Units, shares in Millions, $ in Millions	Jan. 29, 2016$ / shares	Aug. 20, 2015$ / shares	Aug. 04, 2015$ / shares	Dec. 31, 2015USD ($)ami$ / shares	Dec. 31, 2014USD ($)$ / shares	Dec. 31, 2013USD ($)$ / shares	Jul. 01, 2015shares
Basis Of Accounting Presentation [Line Items]
Pipeline Length | mi				15,000
Common Stock, Shares, Issued | shares							317.6
Senior Notes				$ 2,722.3
Repayments of Related Party Debt				1,087.3
Distribution to Parent				1,450	$ 0
Base Gas Purchases				0	0	$ 0
Amortized software costs				8.7	4.3	5
Unamortized software costs				59.8	18.3
Goodwill				1,975.5	1,975.5
Gain (Loss) on Sale of Assets and Asset Impairment Charges				2.4	0	0
Royalty Revenue				26.5	43.8	21.2
Gain on Conveyances				$ 52.3	$ 34.5
Acres | a				460,000
Common Stock, Dividends, Per Share, Cash Paid | $ / shares		$ 0.125		$ 0.25
Common Stock, Dividends, Per Share, Declared | $ / shares			$ 0.125	$ 0.25	$ 0
Dividends Payable, Date of Record			Oct. 30, 2015
Dividends Payable, Date to be Paid			Nov. 20, 2015
Allocated Tax Benefit				$ 5.8	$ 1.3	5.3
Capitalized Exploratory Well Costs that Have Been Capitalized for Period Greater than One Year				$ 0.3
Projects that have Exploratory Well Costs that have been Capitalized for Period Greater than One Year, Number of Projects				1
Millennium Pipeline
Basis Of Accounting Presentation [Line Items]
Equity Method Investment, Ownership Percentage				47.50%
Hardy Storage
Basis Of Accounting Presentation [Line Items]
Percentage of voting power held				50.00%
Pennant
Basis Of Accounting Presentation [Line Items]
Equity Method Investment, Ownership Percentage				47.50%
Equity Method Investment, Initial Ownership Percentage				5.00%
Cash Received from Buy-In				$ 12.7
Gain on Buy-In				$ 2.9
Subsequent Event
Basis Of Accounting Presentation [Line Items]
Common Stock, Dividends, Per Share, Declared | $ / shares	$ 0.12875
Dividends Payable, Date of Record	Feb. 8, 2016
Dividends Payable, Date to be Paid	Feb. 19, 2016
Previous [Member] | Pennant
Basis Of Accounting Presentation [Line Items]
Equity Method Investment, Ownership Percentage				50.00%
Maximum | Pennant
Basis Of Accounting Presentation [Line Items]
Equity Method Investment, Ownership Percentage				33.33%
Predecessor
Basis Of Accounting Presentation [Line Items]
Distribution to Parent						123
Gain on Conveyances						$ 7.3
Common Stock, Dividends, Per Share, Declared | $ / shares						$ 0

Nature Of Operations And Summ58

Nature Of Operations And Summary Of Significant Accounting Policies (Schedule of AFUDC Debt and Equity Rates) (Details)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Columbia Gas Transmission | Debt Rate
Schedule of AFUDC Debt and Equity Rates [Line Items]
Public Utilities, Allowance for Funds Used During Construction, Rate	1.80%	0.90%
Columbia Gas Transmission | Equity Rate
Schedule of AFUDC Debt and Equity Rates [Line Items]
Public Utilities, Allowance for Funds Used During Construction, Rate	6.30%	3.00%
Columbia Gulf | Debt Rate
Schedule of AFUDC Debt and Equity Rates [Line Items]
Public Utilities, Allowance for Funds Used During Construction, Rate	2.90%	2.10%
Columbia Gulf | Equity Rate
Schedule of AFUDC Debt and Equity Rates [Line Items]
Public Utilities, Allowance for Funds Used During Construction, Rate	6.30%	9.40%
Predecessor | Columbia Gas Transmission | Debt Rate
Schedule of AFUDC Debt and Equity Rates [Line Items]
Public Utilities, Allowance for Funds Used During Construction, Rate			2.50%
Predecessor | Columbia Gas Transmission | Equity Rate
Schedule of AFUDC Debt and Equity Rates [Line Items]
Public Utilities, Allowance for Funds Used During Construction, Rate			3.20%
Predecessor | Columbia Gulf | Debt Rate
Schedule of AFUDC Debt and Equity Rates [Line Items]
Public Utilities, Allowance for Funds Used During Construction, Rate			2.50%
Predecessor | Columbia Gulf | Equity Rate
Schedule of AFUDC Debt and Equity Rates [Line Items]
Public Utilities, Allowance for Funds Used During Construction, Rate			3.20%

Nature Of Operations And Summ59

Nature Of Operations And Summary Of Significant Accounting Policies (Computation Of Diluted Average Common Shares) (Details) - shares shares in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Diluted Average Common Shares Computation [Line Items]
Basic average common shares outstanding	328.5	317.6
Shares restricted under stock plans	0.6	0
Diluted Average Common Shares	329.1	317.6
Predecessor
Diluted Average Common Shares Computation [Line Items]
Basic average common shares outstanding			317.6
Shares restricted under stock plans			0
Diluted Average Common Shares			317.6

Nature Of Operations And Summ60

Nature Of Operations And Summary Of Significant Accounting Policies (Schedule of Changes in Capitalized Exploratory Well Costs) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Beginning Balance	$ 14.9	$ 1.9
Capitalized Exploratory Well Cost, Additions Pending Determination of Proved Reserves	1.3	20.1
Reclassification to Well, Facilities, and Equipment Based on Determination of Proved Reserves	(14.5)	(7.1)
Ending Balance	$ 1.7	$ 14.9

CPPL Initial Public Offering (N

CPPL Initial Public Offering (Narrative) (Details) - USD ($) shares in Millions, $ in Millions	11 Months Ended	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2015
Initial Public Offering [Line Items]
Issuance of common units of CPPL	$ 1,168.4	$ 1,168.4
Common Units
Initial Public Offering [Line Items]
Partners' Capital Account, Units, Sold in Public Offering	53.8
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%

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								11 Months Ended	12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2015	Dec. 31, 2014
Initial Public Offering [Line Items]
Net Income (Loss) Allocated to Limited Partners	$ 63.4	$ 63	$ 50.8	$ 90	$ 62.6	$ 53.6	$ 59.1	$ 92.8	$ 267.2	$ 267.2	$ 268.1
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders										23.2
Noncontrolling Interest, Increase from Subsidiary Equity Issuance										0
Change from net income attributable to the Partnership and transfers to noncontrolling interest									494.3
Noncontrolling Interest
Initial Public Offering [Line Items]
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders									$ 227.1	23.2
Noncontrolling Interest, Increase from Subsidiary Equity Issuance										$ (227.1)

Recent Accounting Pronounceme63

Recent Accounting Pronouncements (Narrative) (Details) $ in Millions	Dec. 31, 2015USD ($)
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
Unamortized Debt Issuance Expense	$ 20.6

Transactions with Affiliates (N

Transactions with Affiliates (Narrative) (Details) - USD ($) $ in Millions	11 Months Ended	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Jun. 30, 2015
Related Party Transaction [Line Items]
Interest Expense, Long-term Debt-affiliated		$ 31	$ 61.6
Allowance for Funds Used During Construction, Capitalized Interest		2.4	$ 2.7
Short-term Debt, Weighted Average Interest Rate			0.70%		1.21%
Interest Expense, Short-term Borrowings-affiliated		0.7	$ 3.1
Accounts receivable	$ 0	0	180
Default Provision Floor	50	50
Short-term borrowings-affiliated	0	0	252.5
Repayments of Related Party Debt		1,087.3
Distribution to Parent		1,450	0
Transportation and Storage Services
Related Party Transaction [Line Items]
Accounts receivable			34.5
Predecessor
Related Party Transaction [Line Items]
Interest Expense, Long-term Debt-affiliated				$ 40.6
Allowance for Funds Used During Construction, Capitalized Interest				6.8
Interest Expense, Short-term Borrowings-affiliated				4.1
Distribution to Parent				$ 123
Money Pool
Related Party Transaction [Line Items]
Accounts receivable			$ 145.5
Line of Credit Facility, Maximum Borrowing Capacity	750	750
Revolving Credit Facility
Related Party Transaction [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	1,500	$ 1,500
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	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Related Party Transaction [Line Items]
Transportation revenues	$ 47.5	$ 95.7
Storage revenues	26.2	53.2
Other revenues	0.2	0.3
Operating and maintenance expense	52.9	123.2
Interest expense	29.3	62
Interest income	2.5	0.7
Accounts receivable	0	180
Current portion of long-term debt-affiliated	0	115.9
Short-term borrowings	15	0
Accounts payable	0	53.6
Long-term debt-affiliated	$ 0	$ 1,472.8
Predecessor
Related Party Transaction [Line Items]
Transportation revenues			$ 94.1
Storage revenues			53.6
Other revenues			0.3
Operating and maintenance expense			118.6
Interest expense			37.9
Interest income			$ 0.7

Transactions with Affiliates 66

Transactions with Affiliates (Schedule of Long-term Debt) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014
Schedule of Related Party Transactions, Long-Term Debt [Line Items]
Long Term Debt		$ 0	$ 1,588.7
Notes Due 2015
Schedule of Related Party Transactions, Long-Term Debt [Line Items]
Debt Instrument, Issuance Date		Nov. 28, 2005
Debt Instrument, Interest Rate, Stated Percentage		5.41%
Debt Instrument, Maturity Date		Nov. 30, 2015
Long Term Debt	[1]	$ 0	115.9
Notes Due 2016
Schedule of Related Party Transactions, Long-Term Debt [Line Items]
Debt Instrument, Issuance Date		Nov. 28, 2005
Debt Instrument, Interest Rate, Stated Percentage		5.45%
Debt Instrument, Maturity Date		Nov. 28, 2016
Long Term Debt		$ 0	45.3
Notes Due 2025
Schedule of Related Party Transactions, Long-Term Debt [Line Items]
Debt Instrument, Issuance Date		Nov. 28, 2005
Debt Instrument, Interest Rate, Stated Percentage		5.92%
Debt Instrument, Maturity Date		Nov. 28, 2025
Long Term Debt		$ 0	133.5
Notes Due 2032
Schedule of Related Party Transactions, Long-Term Debt [Line Items]
Debt Instrument, Issuance Date		Nov. 28, 2012
Debt Instrument, Interest Rate, Stated Percentage		4.63%
Debt Instrument, Maturity Date		Nov. 28, 2032
Long Term Debt		$ 0	45
Notes Due 2037
Schedule of Related Party Transactions, Long-Term Debt [Line Items]
Debt Instrument, Issuance Date		Nov. 28, 2012
Debt Instrument, Interest Rate, Stated Percentage		4.94%
Debt Instrument, Maturity Date		Nov. 30, 2037
Long Term Debt		$ 0	95
Notes Due 2037 [1]
Schedule of Related Party Transactions, Long-Term Debt [Line Items]
Debt Instrument, Issuance Date		Dec. 19, 2012
Debt Instrument, Interest Rate, Stated Percentage		5.16%
Debt Instrument, Maturity Date		Dec. 21, 2037
Long Term Debt		$ 0	55
Notes Due 2042
Schedule of Related Party Transactions, Long-Term Debt [Line Items]
Debt Instrument, Issuance Date		Nov. 28, 2012
Debt Instrument, Interest Rate, Stated Percentage		5.26%
Debt Instrument, Maturity Date		Nov. 28, 2042
Long Term Debt		$ 0	170
Notes Due 2042 [1]
Schedule of Related Party Transactions, Long-Term Debt [Line Items]
Debt Instrument, Issuance Date		Dec. 19, 2012
Debt Instrument, Interest Rate, Stated Percentage		5.49%
Debt Instrument, Maturity Date		Dec. 18, 2042
Long Term Debt		$ 0	95
Notes Due 2016 [1]
Schedule of Related Party Transactions, Long-Term Debt [Line Items]
Debt Instrument, Issuance Date		Dec. 9, 2013
Debt Instrument, Interest Rate, Stated Percentage		4.75%
Debt Instrument, Maturity Date		Dec. 31, 2016
Long Term Debt		$ 0	$ 834
[1]	The debt balance for the note originating on November 28, 2005 and maturing on November 30, 2015 is included in "Current portion of long-term debt-affiliated" on the Consolidated Balance Sheets as of December 31, 2014.

Short-Term Borrowings (Narrativ

Short-Term Borrowings (Narrative) (Details) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2015USD ($)$ / shares	Dec. 31, 2014USD ($)	Dec. 05, 2014USD ($)
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
Commercial paper outstanding	0	$ 0
Letter of Credit
Short-term Debt [Line Items]
Revolving credit facility, maximum	250
Commercial Paper
Short-term Debt [Line Items]
Revolving credit facility, maximum	1,000
Revolving Credit Facility
Short-term Debt [Line Items]
Revolving credit facility, maximum	1,500
Letters of Credit Outstanding, Amount	18.1
Line of Credit Facility, Amount Outstanding	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	50
CPPL | Revolving Credit Facility
Short-term Debt [Line Items]
Revolving credit facility, maximum			$ 500
Letters of Credit Outstanding, Amount	0
Line of Credit Facility, Amount Outstanding	$ 15	$ 0
Federal Funds Effective Swap Rate
Short-term Debt [Line Items]
Debt Instrument, Basis Spread on Variable Rate	0.50%
London Interbank Offered Rate (LIBOR)
Short-term Debt [Line Items]
Debt Instrument, Basis Spread on Variable Rate	1.00%
Eurodollar
Short-term Debt [Line Items]
Margin Rate	1.00%
Minimum
Short-term Debt [Line Items]
Line of Credit Facility, Commitment Fee Percentage	0.125%
Minimum quarterly distribution | $ / shares	$ 0.1675
Minimum | London Interbank Offered Rate (LIBOR)
Short-term Debt [Line Items]
Margin Rate	0.00%
Minimum | Eurodollar
Short-term Debt [Line Items]
Margin Rate	1.00%
Maximum
Short-term Debt [Line Items]
Ratio of Indebtedness to Net Capital	1
Line of Credit Facility, Commitment Fee Percentage	0.35%
Maximum | London Interbank Offered Rate (LIBOR)
Short-term Debt [Line Items]
Margin Rate	0.65%
Maximum | Eurodollar
Short-term Debt [Line Items]
Margin Rate	1.65%
Period 1 | Minimum
Short-term Debt [Line Items]
Ratio of Indebtedness to Net Capital	5.75
Period 1 | Maximum
Short-term Debt [Line Items]
Ratio of Indebtedness to Net Capital	1
Period 2 | Minimum
Short-term Debt [Line Items]
Ratio of Indebtedness to Net Capital	5.50
Period 2 | Maximum
Short-term Debt [Line Items]
Ratio of Indebtedness to Net Capital	1
Period 3 | Minimum
Short-term Debt [Line Items]
Ratio of Indebtedness to Net Capital	5
Period 3 | 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

Short-Term Borrowings (Schedule

Short-Term Borrowings (Schedule Of Short-Term Borrowings) (Details) - USD ($) $ in Millions	Dec. 31, 2015	Jun. 30, 2015	Dec. 31, 2014
Short-term Debt [Line Items]
Commercial paper	$ 0		$ 0
Short-term Debt, Weighted Average Interest Rate		1.21%	0.70%
Short-term borrowings	$ 15		$ 0
Commercial Paper
Short-term Debt [Line Items]
Short-term Debt, Weighted Average Interest Rate	0.00%		0.00%
Revolving Credit Facility
Short-term Debt [Line Items]
Credit facilities borrowings	$ 0		$ 0
Short-term Debt, Weighted Average Interest Rate	0.00%		0.00%
CPPL | Revolving Credit Facility
Short-term Debt [Line Items]
Credit facilities borrowings	$ 15		$ 0
Short-term Debt, Weighted Average Interest Rate	1.28%		0.00%

Long-Term Debt (Narrative) (Det

Long-Term Debt (Narrative) (Details) - USD ($) $ in Millions	May. 22, 2015	Dec. 31, 2015
Debt Instrument [Line Items]
Senior Notes		$ 2,722.3
Debt Covenant Interest Increase		0.50%
Debt Instrument, Unamortized Discount		$ 3.8
Senior Notes
Debt Instrument [Line Items]
Face amount of notes		$ 2,750
Debt Instrument, Issuance Date	May 22, 2015
Notes Due 2018 | Senior Notes
Debt Instrument [Line Items]
Face amount of notes	$ 500
Debt Instrument, Interest Rate, Stated Percentage	2.45%
Debt Instrument, Maturity Date	Jun. 1, 2018
Notes Due 2020 | Senior Notes
Debt Instrument [Line Items]
Face amount of notes	$ 750
Debt Instrument, Interest Rate, Stated Percentage	3.30%
Debt Instrument, Maturity Date	Jun. 1, 2020
Notes Due 2025
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		5.92%
Debt Instrument, Issuance Date		Nov. 28, 2005
Debt Instrument, Maturity Date		Nov. 28, 2025
Notes Due 2025 | Senior Notes
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
Notes Due 2045 | Senior Notes
Debt Instrument [Line Items]
Face amount of notes	$ 500
Debt Instrument, Interest Rate, Stated Percentage	5.80%
Debt Instrument, Maturity Date	Jun. 1, 2045

Long-Term Debt (Schedule Of Out

Long-Term Debt (Schedule Of Outstanding Long Term Debt Maturities) (Details) $ in Millions	Dec. 31, 2015USD ($)
Debt Instrument [Line Items]
2,016	$ 0
2,017	0
2,018	500
2,019	0
2,020	750
After	1,500
Total long-term debt	$ 2,750	[1]
[1]	This amount excludes unamortized discount of $3.8 million. The unamortized discount applicable to the Notes is being amortized over the weighted average life of the Notes.

Gain on Sale of Assets (Details

Gain on Sale of Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Property, Plant and Equipment [Line Items]
Gain on Conveyances	$ 52.3	$ 34.5
Gain on Conveyances Cash Received	35.8
Deferred Gains On Conveyances	8.1	19.6
Gain (Loss) on Disposition of Property Plant Equipment	$ 52.9	$ 34.5
Gas Stored Base Gas
Property, Plant and Equipment [Line Items]
Gain (Loss) on Disposition of Property Plant Equipment			$ 11.1
Predecessor
Property, Plant and Equipment [Line Items]
Gain on Conveyances			7.3
Gain (Loss) on Disposition of Property Plant Equipment			$ 18.6

Property, Plant And Equipment72

Property, Plant And Equipment (Schedule Of Property, Plant And Equipment) (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Property Plant and Equipment	$ 9,052.3	$ 7,935.4
Accumulated Depreciation and Amortization	(2,988.6)	(2,976.8)
Net Property, Plant and Equipment	6,063.7	4,958.6
Pipeline and Other Transmission Assets
Property, Plant and Equipment [Line Items]
Property Plant and Equipment	6,160.4	5,333
Storage Facilities
Property, Plant and Equipment [Line Items]
Property Plant and Equipment	1,370.1	1,326.5
Gas Stored Base Gas
Property, Plant and Equipment [Line Items]
Property Plant and Equipment	299.5	299.5
Gathering and Processing Facilities
Property, Plant and Equipment [Line Items]
Property Plant and Equipment	370.2	263.3
Construction Work In Process
Property, Plant and Equipment [Line Items]
Property Plant and Equipment	487.6	454.2
General Plant, Software, and Other Assets
Property, Plant and Equipment [Line Items]
Property Plant and Equipment	$ 364.5	$ 258.9

Property, Plant And Equipment73

Property, Plant And Equipment (Schedule of Depreciation Rates) (Details)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Pipeline and Other Transmission Assets | Minimum
Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Disclosure of Composite Depreciation Rate for Plants in Service	1.00%	1.00%
Pipeline and Other Transmission Assets | Maximum
Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Disclosure of Composite Depreciation Rate for Plants in Service	2.50%	2.50%
Storage Facilities | Minimum
Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Disclosure of Composite Depreciation Rate for Plants in Service	2.19%	2.19%
Storage Facilities | Maximum
Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Disclosure of Composite Depreciation Rate for Plants in Service	3.00%	3.30%
Gathering and Processing Facilities | Minimum
Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Disclosure of Composite Depreciation Rate for Plants in Service	1.67%	1.67%
Gathering and Processing Facilities | Maximum
Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Disclosure of Composite Depreciation Rate for Plants in Service	2.50%	2.50%
General Plant, Software, and Other Assets | Minimum
Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Disclosure of Composite Depreciation Rate for Plants in Service	1.00%	1.00%
General Plant, Software, and Other Assets | Maximum
Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Disclosure of Composite Depreciation Rate for Plants in Service	21.00%	10.00%
Predecessor | Pipeline and Other Transmission Assets | Minimum
Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Disclosure of Composite Depreciation Rate for Plants in Service			1.00%
Predecessor | Pipeline and Other Transmission Assets | Maximum
Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Disclosure of Composite Depreciation Rate for Plants in Service			2.50%
Predecessor | Storage Facilities | Minimum
Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Disclosure of Composite Depreciation Rate for Plants in Service			2.19%
Predecessor | Storage Facilities | Maximum
Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Disclosure of Composite Depreciation Rate for Plants in Service			3.50%
Predecessor | Gathering and Processing Facilities | Minimum
Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Disclosure of Composite Depreciation Rate for Plants in Service			1.67%
Predecessor | Gathering and Processing Facilities | Maximum
Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Disclosure of Composite Depreciation Rate for Plants in Service			2.50%
Predecessor | General Plant, Software, and Other Assets | Minimum
Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Disclosure of Composite Depreciation Rate for Plants in Service			1.00%
Predecessor | General Plant, Software, and Other Assets | Maximum
Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Disclosure of Composite Depreciation Rate for Plants in Service			10.00%

Goodwill (Details)

Goodwill (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Goodwill And Other Intangible Assets [Line Items]
Goodwill	$ 1,975.5	$ 1,975.5
Goodwill, Impairment Loss	$ 0
Columbia Gas Transmission
Goodwill And Other Intangible Assets [Line Items]
Fair Value Inputs, Discount Rate	5.60%
Fair value amount above carrying value of goodwill	$ 1,643

Asset Retirement Obligations (C

Asset Retirement Obligations (Changes In Company's Liability For Asset Retirement Obligations) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Asset Retirement Obligation [Abstract]
Beginning Balance	$ 23.2	$ 26.3
Accretion expense	1.2	1.5
Additions	4.1	2.2
Settlements	0	(6.6)
Change in estimated cash flows	(2.8)	(0.2)
Ending Balance	$ 25.7	$ 23.2

Regulatory Matters (Narrative)

Regulatory Matters (Narrative) (Details) - USD ($) $ in Millions	Jan. 28, 2016	Jan. 01, 2015	Jan. 24, 2013	Dec. 31, 2015
Regulatory Matters [Line Items]
Regulatory asset not earning return on investment				$ 0
Expenses recovered as components of cost of service and regulatory orders				$ 35.6
Remaining life for the costs to be recovered, years				7 years
Customer Refund			$ 88.1
Initial Customer Refund			50
Total Capital Cost Recovery Mechanism Over Five-year Term			$ 1,500
Depreciation Rate Reduction			1.50%
Annual base rate reduction effective January 1, 2014			$ 25
Capital Cost Recovery Mechanism Revenue Requirement			14.00%
Required Annual Capital Maintenance Expenditure			$ 100
Annual Capital Cost Recovery Mechanism Limit			$ 1,500
Expected Modernization Investment		$ 300
Annual Capital Cost Recovery Mechanism Limit Tolerance			15.00%
Subsequent Event
Regulatory Matters [Line Items]
Expected Modernization Investment	$ 937.1

Regulatory Matters (Regulatory

Regulatory Matters (Regulatory Assets) (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Regulatory Assets [Line Items]
Total Assets	$ 182.7	$ 158
Unrecognized Pension Benefit And Other Postretirement Benefit Costs
Regulatory Assets [Line Items]
Total Assets	135.2	120.9
Other Postretirement Costs
Regulatory Assets [Line Items]
Total Assets	9	10.8
Deferred Taxes on AFUDC Equity
Regulatory Assets [Line Items]
Total Assets	35.4	21.8
Other
Regulatory Assets [Line Items]
Total Assets	$ 3.1	$ 4.5

Regulatory Matters (Regulator78

Regulatory Matters (Regulatory Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities reflected in Current Regulatory Liabilities and Other Regulatory Liabilities and Other Removal Costs	$ 322.8	$ 297
Cost Of Removal
Regulatory Liabilities [Line Items]
Total Liabilities	154.7	157.6
Regulatory Effects Of Accounting For Income Taxes
Regulatory Liabilities [Line Items]
Total Liabilities	10.6	10.9
Unrecognized Pension Benefit And Other Postretirement Benefit Costs
Regulatory Liabilities [Line Items]
Total Liabilities	0.7	8.3
Other Postretirement Costs
Regulatory Liabilities [Line Items]
Total Liabilities	155.6	117.3
Other
Regulatory Liabilities [Line Items]
Total Liabilities	$ 1.2	$ 2.9

Equity Method Investments (Narr

Equity Method Investments (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Schedule of Equity Method Investments [Line Items]
Utilities Operating Expense, Maintenance and Operations	$ 652.1	$ 628.4
Millennium Pipeline
Schedule of Equity Method Investments [Line Items]
Utilities Operating Expense, Maintenance and Operations	$ 13.1

Equity Method Investments (Sche

Equity Method Investments (Schedule Of Equity Method Investments) (Details)	Dec. 31, 2015
Hardy Storage Company, LLC
Schedule of Equity Method Investments [Line Items]
Percentage of voting power held	50.00%
LLC Membership | Pennant Midstream, LLC
Schedule of Equity Method Investments [Line Items]
Percentage of voting power held	47.50%

Equity Method Investments (Sc81

Equity Method Investments (Schedule Of Immaterial Nature Of Equity Investments) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Millennium Pipeline
Schedule of Equity Method Investments [Line Items]
Net Revenues		$ 206.3	$ 190.5
Operating Income		136.1	128.8
Net Income		98	89.6
Current Assets		35.7	32.1
Noncurrent Assets		987.1	1,016.3
Current Liabilities		44.4	42.6
Noncurrent Liabilities		535.8	568.3
Total Members' Equity		442.6	437.5
Contributions	[1]	1.4	2.6
Distribution of Earnings	[1]	47.5	35.6
Millennium Pipeline | Predecessor
Schedule of Equity Method Investments [Line Items]
Net Revenues				$ 157.8
Operating Income				101.3
Net Income				63
Current Assets				38.3
Noncurrent Assets				1,033.8
Current Liabilities				58.8
Noncurrent Liabilities				599.7
Total Members' Equity				413.6
Contributions	[1]			16.6
Distribution of Earnings	[1]			29
Hardy Storage
Schedule of Equity Method Investments [Line Items]
Net Revenues		23.4	23.6
Operating Income		15.3	16.1
Net Income		10.3	10.6
Current Assets		12.1	12
Noncurrent Assets		155.5	157.4
Current Liabilities		19.3	17.1
Noncurrent Liabilities		68.5	77.4
Total Members' Equity		79.8	74.9
Contributions	[1]	0	0
Distribution of Earnings	[1]	2.6	2.2
Hardy Storage | Predecessor
Schedule of Equity Method Investments [Line Items]
Net Revenues				24.4
Operating Income				16.5
Net Income				10.6
Current Assets				12.5
Noncurrent Assets				160.2
Current Liabilities				18.3
Noncurrent Liabilities				85.7
Total Members' Equity				68.7
Contributions	[1]			0
Distribution of Earnings	[1]			3.1
Pennant
Schedule of Equity Method Investments [Line Items]
Net Revenues		34.6	8.5
Operating Income		17.8	(2.4)
Net Income		17.8	(2.4)
Current Assets		11	23.7
Noncurrent Assets		389.6	380
Current Liabilities		8.4	8.6
Total Members' Equity		392.2	395.1
Contributions	[1]	0	66.6
Distribution of Earnings	[1]	7.1	0
Return of Capital	[1]	$ 16	$ 0
Pennant | Predecessor
Schedule of Equity Method Investments [Line Items]
Net Revenues				2
Operating Income				1.3
Net Income				1.3
Current Assets				34.1
Noncurrent Assets				231.9
Current Liabilities				11.4
Total Members' Equity				254.6
Contributions	[1]			108.9
Distribution of Earnings	[1]			0
Return of Capital	[1]			$ 0
[1]	Contribution and distribution data represents CPG's portion based on CPG's ownership percentage of each investment.

Income Taxes (Narrative) (Detai

Income Taxes (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax [Line Items]
Effective income tax rates	33.20%	38.70%
Increase (Decrease) in Effective Tax Rate	(5.50%)
Remaining carry forwards	$ 127.7
Tax Credit Carryforward, Expiration Date	Dec. 31, 2035
Expected benefits to be realized	$ 13.7
Unrecognized tax benefits, if recognized, would affect effective tax rate	(0.4)	$ 0	$ (0.1)
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense	$ 0
2015-2017
Income Tax [Line Items]
Bonus Depreciation Phase Down Rate	50.00%
2,018
Income Tax [Line Items]
Bonus Depreciation Phase Down Rate	40.00%
2,019
Income Tax [Line Items]
Bonus Depreciation Phase Down Rate	30.00%
Predecessor
Income Tax [Line Items]
Effective income tax rates			35.00%

Income Taxes (Schedule Of Compo

Income Taxes (Schedule Of Components Of Income Tax Expense) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Schedule of Income Tax Expense/Benefit [Line Items]
Current federal income taxes	$ 12.1	$ 19.5
Current state income taxes	9.1	7.6
Total current income taxes	21.2	27.1
Deferred federal income taxes	120.2	119.2
Deferred state income taxes	11.6	23.5
Total deferred income taxes	131.8	142.7
Deferred Investment Credits	0	(0.1)
Income Taxes from Continuing Operations	$ 153	$ 169.7
Predecessor
Schedule of Income Tax Expense/Benefit [Line Items]
Current federal income taxes			$ (15.5)
Current state income taxes			(11.9)
Total current income taxes			(27.4)
Deferred federal income taxes			157.4
Deferred state income taxes			16.6
Total deferred income taxes			174
Deferred Investment Credits			(0.1)
Income Taxes from Continuing Operations			$ 146.5

Income Taxes (Schedule Of Reaso

Income Taxes (Schedule Of Reasons Behind Differences In Computation Of Total Income Taxes) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Schedule of Reasons Behind Differences in Computation of Total Income Taxes [Line Items]
Income (Loss) from Continuing Operations before Income Taxes, Extraordinary Items, Noncontrolling Interest	$ 460.5	$ 438.4
Tax expense at statutory federal income tax rate, value	$ 161.2	$ 153.5
Tax expense at statutory federal income tax rate, rate	35.00%	35.00%
State income taxes, net of federal income tax benefit, value	$ 13.4	$ 20.3
State income taxes, net of federal income tax benefit, rate	2.90%	4.60%
Regulatory treatment of depreciation differences, value	$ (14)	$ 0
Regulatory treatment of depreciation differences, rate	(3.00%)	0.00%
Regulatory treatment of AFUDC-Equity, value	$ (9.2)	$ (3.7)
Regulatory treatment of AFUDC-Equity, rate	(2.00%)	(0.80%)
Tax accrual adjustments and other, net, value	$ 1.6	$ (0.4)
Effective Income Tax Rate Reconciliation, Other Adjustments, Percent	0.30%	(0.10%)
Income Taxes from Continuing Operations	$ 153	$ 169.7
Income Taxes from Continuing Operations, rate	33.20%	38.70%
Predecessor
Schedule of Reasons Behind Differences in Computation of Total Income Taxes [Line Items]
Income (Loss) from Continuing Operations before Income Taxes, Extraordinary Items, Noncontrolling Interest			$ 418.2
Tax expense at statutory federal income tax rate, value			$ 146.4
Tax expense at statutory federal income tax rate, rate			35.00%
State income taxes, net of federal income tax benefit, value			$ 3
State income taxes, net of federal income tax benefit, rate			0.70%
Regulatory treatment of depreciation differences, value			$ 0
Regulatory treatment of depreciation differences, rate			0.00%
Regulatory treatment of AFUDC-Equity, value			$ (2.4)
Regulatory treatment of AFUDC-Equity, rate			(0.60%)
Tax accrual adjustments and other, net, value			$ (0.5)
Effective Income Tax Rate Reconciliation, Other Adjustments, Percent			(0.10%)
Income Taxes from Continuing Operations			$ 146.5
Income Taxes from Continuing Operations, rate			35.00%

Income Taxes (Schedule Of Princ

Income Taxes (Schedule Of Principal Components Of Net Deferred Tax Liability) (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Schedule of Principal Components of Net Tax Expense [Line Items]
Accelerated depreciation and other property differences	$ 1,429.2	$ 1,235.2
Pension and Other Postretirement/Postemployment Benefits	29.9	27.7
Other regulatory assets	71.8	62.8
Equity Method Investments	124.3	99.2
Deferred Tax Liabilities, Gross	1,655.2	1,424.9
Other regulatory liabilities	(126.8)	(116.7)
Net operating loss carryforward	(141.4)	(70.3)
Other	(38.9)	(42.2)
Total Deferred Tax Assets	(307.1)	(229.2)
Net Deferred Tax Liabilities	1,348.1	1,195.7
Less: Deferred income taxes related to current assets and liabilities	0	(60)
Non-Current Deferred Tax Liability	$ 1,348.1	$ 1,255.7

Pension And Other Postretirem86

Pension And Other Postretirement Benefits (Narrative) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets			$ 586	$ 574.8
Decrease In Net Periodic Benefit Cost			(1.9)
Regulatory assets			182.7	158
Defined Benefit Plan, Accumulated Benefit Obligation			404.5	397.6
Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets			357.8	351	$ 344.5
Defined Benefit Plan, Actuarial Gain (Loss)	[1]		(6.9)	22.7
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)			(1.1)	(1.1)
Defined Benefit Plan, Net Periodic Benefit Cost			1.5	(0.4)
Employer contributions			20	7.7
Expected contribution			0.8
Funded status of plan			$ 46.7	$ 46.6
Expected return on plan assets			8.20%	8.30%
Defined Benefit Plan, Recognized Net (Gain) Loss Due to Settlements			$ 0	$ 0
Change in Net Periodic Benefit Cost due to Interim Measurement					1.3
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets			228.2	223.8	209.7
Defined Benefit Plan, Actuarial Gain (Loss)	[1]		(12.4)	5.7
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)			(0.3)	0.1
Defined Benefit Plan, Net Periodic Benefit Cost			(13)	(10.8)
Employer contributions			13.5	11.9
Expected contribution			2.2
Increase in funded status other postretirement benefit plans			16.5
Funded status of plan			$ (116.1)	$ (99.6)
Expected return on plan assets			8.05%	8.14%
Defined Benefit Plan, Recognized Net (Gain) Loss Due to Settlements			$ 0	$ 0
Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets			$ 0	$ 17.6	18.9
Percentage of investments			0.00%	3.00%
Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets			$ 0	$ 0
Unrecognized Pension Benefit And Other Postretirement Benefit Costs
Defined Benefit Plan Disclosure [Line Items]
Regulatory liabilities			0.7	8.3
Predecessor | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)					(1.1)
Defined Benefit Plan, Net Periodic Benefit Cost					$ 19
Expected return on plan assets					8.30%
Defined Benefit Plan, Recognized Net (Gain) Loss Due to Settlements					$ 13.8
Predecessor | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)					0.1
Defined Benefit Plan, Net Periodic Benefit Cost					$ (5.8)
Expected return on plan assets					8.17%
Defined Benefit Plan, Recognized Net (Gain) Loss Due to Settlements					$ 0
Scenario, Forecast | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Actuarial Gain (Loss)		$ 12.4
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)		(1.2)
Amortization of transition obligation		0
Scenario, Forecast | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Actuarial Gain (Loss)		0.2
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)		(0.7)
Amortization of transition obligation		$ 0
Unrecognized Pension Benefit And Other Postretirement Benefit Costs
Defined Benefit Plan Disclosure [Line Items]
Regulatory assets			$ 135.2	$ 120.9
[1]	The change in benefit obligation for Pension Benefits represents the change in Projected Benefit Obligation while the change in benefit obligation for Other Postretirement Benefits represents the change in Accumulated Postretirement Benefit Obligation.

Pension And Other Postretirem87

Pension And Other Postretirement Benefits (Schedule Of Portfolio Asset Mix) (Details)	12 Months Ended
	Dec. 31, 2015
Domestic Equities [Member] | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Equities, Minimum	25.00%
Equities, Maximum	45.00%
Domestic Equities [Member] | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Equities, Minimum	35.00%
Equities, Maximum	55.00%
International Equities [Member] | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Equities, Minimum	15.00%
Equities, Maximum	25.00%
International Equities [Member] | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Equities, Minimum	15.00%
Equities, Maximum	25.00%
Fixed Income [Member] | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Equities, Minimum	23.00%
Equities, Maximum	37.00%
Fixed Income [Member] | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Equities, Minimum	20.00%
Equities, Maximum	50.00%
Real Estate/Private Equity/Hedge Funds [Member] | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Equities, Minimum	0.00%
Equities, Maximum	15.00%
Real Estate/Private Equity/Hedge Funds [Member] | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Equities, Minimum	0.00%
Equities, Maximum	0.00%
Short-Term Investments [Member] | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Equities, Minimum	0.00%
Equities, Maximum	10.00%
Short-Term Investments [Member] | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Equities, Minimum	0.00%
Equities, Maximum	10.00%

Pension And Other Postretirem88

Pension And Other Postretirement Benefits (Schedule Of Pension Plan And Postretirement Plan Asset Mix) (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset	$ 586	$ 574.8
Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Percentage of total asset	100.00%	100.00%
Fair value of asset	$ 357.8	$ 351	$ 344.5
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Percentage of total asset	100.00%	100.00%
Fair value of asset	$ 228.2	$ 223.8	$ 209.7
Domestic Equities [Member] | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Percentage of total asset	39.40%	41.10%
Fair value of asset	$ 141	$ 144.2
Domestic Equities [Member] | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Percentage of total asset	44.40%	47.20%
Fair value of asset	$ 101.6	$ 105.7
International Equities [Member] | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Percentage of total asset	17.50%	18.10%
Fair value of asset	$ 62.5	$ 63.3
International Equities [Member] | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Percentage of total asset	18.80%	18.40%
Fair value of asset	$ 42.8	$ 41.2
Fixed Income [Member] | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Percentage of total asset	34.40%	34.40%
Fair value of asset	$ 123.3	$ 120.9
Fixed Income [Member] | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Percentage of total asset	33.60%	34.10%
Fair value of asset	$ 76.6	$ 76.3
Real Estate/Private Equity/Hedge Funds [Member] | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Percentage of total asset		5.00%
Fair value of asset		$ 17.7
Real Estate/Private Equity/Hedge Funds [Member] | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Percentage of total asset		0.00%
Fair value of asset		$ 0
Cash/Other [Member] | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Percentage of total asset	8.70%	1.40%
Fair value of asset	$ 31	$ 4.9
Cash/Other [Member] | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Percentage of total asset	3.20%	0.30%
Fair value of asset	$ 7.2	$ 0.6

Pension And Other Postretirem89

Pension And Other Postretirement Benefits (Schedule Of Fair Value Of Pension Plan Assets) (Details) - USD ($) $ in Millions		Dec. 31, 2015		Dec. 31, 2014		Dec. 31, 2013
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset		$ (586)		$ (574.8)
Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset		(214.5)		(247.3)
Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset		(371.3)		(309.2)
Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset		0		(17.6)		$ (18.9)
Due To Brokers Net [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset		(0.4)	[1]	(0.1)	[2]
Accrued Investment Income Dividends [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset		(0.6)		(0.1)
Receivables/Payables [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset				(0.7)
Fixed Income Securities [Member] | Other Fixed Income [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset		0		(0.1)		0
Private Equity Limited Partnerships [Member] | U.S. Multi-Strategy [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset		0		(8.5)		(8.7)
Private Equity Limited Partnerships [Member] | International Multi-Strategy [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset		0		(5.3)		(5.8)
Private Equity Limited Partnerships [Member] | Distressed Opportunities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset		0		(1.1)		(1.4)
Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset		(357.8)		(351)		(344.5)
Defined Benefit Plan Fair Value Of Plan Assets Before Pending Items		357.6		350.3
Pension Plan | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets Before Pending Items		7.5		38.6
Pension Plan | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets Before Pending Items		350.1		294.1
Pension Plan | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets Before Pending Items		0		17.6
Pension Plan | Cash [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset		(0.9)		(2.6)
Pension Plan | Cash [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset		(0.9)		(2.6)
Pension Plan | Cash [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset		0		0
Pension Plan | Cash [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset		0		0
Pension Plan | International Equities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset		(62.5)		(63.3)
Pension Plan | Fixed Income [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset		(123.3)		(120.9)
Pension Plan | Equity Securities [Member] | U.S. Equities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset				(0.1)
Pension Plan | Equity Securities [Member] | U.S. Equities [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset				(0.1)
Pension Plan | Equity Securities [Member] | U.S. Equities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset				0
Pension Plan | Equity Securities [Member] | U.S. Equities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset				0
Pension Plan | Equity Securities [Member] | International Equities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset		(6.6)		(20.3)
Pension Plan | Equity Securities [Member] | International Equities [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset		(6.6)		(20.2)
Pension Plan | Equity Securities [Member] | International Equities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset		0		(0.1)
Pension Plan | Equity Securities [Member] | International Equities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset		0		0
Pension Plan | Fixed Income Securities [Member] | Government [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset		(8.5)		(17.8)
Pension Plan | Fixed Income Securities [Member] | Government [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset		0		(15.7)
Pension Plan | Fixed Income Securities [Member] | Government [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset		(8.5)		(2.1)
Pension Plan | Fixed Income Securities [Member] | Government [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset		0		0
Pension Plan | Fixed Income Securities [Member] | Corporate [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset		(13)		(38.7)
Pension Plan | Fixed Income Securities [Member] | Corporate [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset		0		0
Pension Plan | Fixed Income Securities [Member] | Corporate [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset		(13)		(38.7)
Pension Plan | Fixed Income Securities [Member] | Corporate [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset		0		0
Pension Plan | Fixed Income Securities [Member] | Mortgages/Asset Backed Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset				(0.4)
Pension Plan | Fixed Income Securities [Member] | Mortgages/Asset Backed Securities [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset				0
Pension Plan | Fixed Income Securities [Member] | Mortgages/Asset Backed Securities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset				(0.4)
Pension Plan | Fixed Income Securities [Member] | Mortgages/Asset Backed Securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset				0
Pension Plan | Fixed Income Securities [Member] | Other Fixed Income [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset				(0.1)
Pension Plan | Fixed Income Securities [Member] | Other Fixed Income [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset				0
Pension Plan | Fixed Income Securities [Member] | Other Fixed Income [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset				0
Pension Plan | Fixed Income Securities [Member] | Other Fixed Income [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset				(0.1)
Pension Plan | Commingled Funds [Member] | U.S. Equities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset		(141)		(144.2)
Pension Plan | Commingled Funds [Member] | U.S. Equities [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset		0		0
Pension Plan | Commingled Funds [Member] | U.S. Equities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset		(141)		(144.2)
Pension Plan | Commingled Funds [Member] | U.S. Equities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset		0		0
Pension Plan | Commingled Funds [Member] | International Equities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset		(55.6)		(42.1)
Pension Plan | Commingled Funds [Member] | International Equities [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset		0		0
Pension Plan | Commingled Funds [Member] | International Equities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset		(55.6)		(42.1)
Pension Plan | Commingled Funds [Member] | International Equities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset		0		0
Pension Plan | Commingled Funds [Member] | Short-Term Money Markets [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset		(31.1)		(4.9)
Pension Plan | Commingled Funds [Member] | Short-Term Money Markets [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset		0		0
Pension Plan | Commingled Funds [Member] | Short-Term Money Markets [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset		(31.1)		(4.9)
Pension Plan | Commingled Funds [Member] | Short-Term Money Markets [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset		0		0
Pension Plan | Commingled Funds [Member] | Fixed Income [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset		(100.9)		(61.6)
Pension Plan | Commingled Funds [Member] | Fixed Income [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset		0		0
Pension Plan | Commingled Funds [Member] | Fixed Income [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset		(100.9)		(61.6)
Pension Plan | Commingled Funds [Member] | Fixed Income [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset		0		0
Pension Plan | Private Equity Limited Partnerships [Member] | U.S. Multi-Strategy [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset	[3]			(8.5)
Pension Plan | Private Equity Limited Partnerships [Member] | U.S. Multi-Strategy [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset	[3]			0
Pension Plan | Private Equity Limited Partnerships [Member] | U.S. Multi-Strategy [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset	[3]			0
Pension Plan | Private Equity Limited Partnerships [Member] | U.S. Multi-Strategy [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset	[3]			(8.5)
Pension Plan | Private Equity Limited Partnerships [Member] | International Multi-Strategy [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset	[4]			(5.3)
Pension Plan | Private Equity Limited Partnerships [Member] | International Multi-Strategy [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset	[4]			0
Pension Plan | Private Equity Limited Partnerships [Member] | International Multi-Strategy [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset	[4]			0
Pension Plan | Private Equity Limited Partnerships [Member] | International Multi-Strategy [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset	[4]			(5.3)
Pension Plan | Private Equity Limited Partnerships [Member] | Distressed Opportunities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset				(1.1)
Pension Plan | Private Equity Limited Partnerships [Member] | Distressed Opportunities [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset				0
Pension Plan | Private Equity Limited Partnerships [Member] | Distressed Opportunities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset				0
Pension Plan | Private Equity Limited Partnerships [Member] | Distressed Opportunities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset				(1.1)
Pension Plan | Real Estate [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset				(2.6)
Pension Plan | Real Estate [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset				0
Pension Plan | Real Estate [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset				0
Pension Plan | Real Estate [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset				(2.6)
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset		(228.2)		(223.8)		$ (209.7)
Other Postretirement Benefits | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset		(207)		(208.7)
Other Postretirement Benefits | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset		(21.2)		(15.1)
Other Postretirement Benefits | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset		0		0
Other Postretirement Benefits | International Equities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset		(42.8)		(41.2)
Other Postretirement Benefits | Fixed Income [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset		(76.6)		(76.3)
Other Postretirement Benefits | Commingled Funds [Member] | U.S. Equities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset		(13.9)		(14.3)
Other Postretirement Benefits | Commingled Funds [Member] | U.S. Equities [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset		0		0
Other Postretirement Benefits | Commingled Funds [Member] | U.S. Equities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset		(13.9)		(14.3)
Other Postretirement Benefits | Commingled Funds [Member] | U.S. Equities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset		0		0
Other Postretirement Benefits | Commingled Funds [Member] | Short-Term Money Markets [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset		(7.3)		(0.8)
Other Postretirement Benefits | Commingled Funds [Member] | Short-Term Money Markets [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset		0		0
Other Postretirement Benefits | Commingled Funds [Member] | Short-Term Money Markets [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset		(7.3)		(0.8)
Other Postretirement Benefits | Commingled Funds [Member] | Short-Term Money Markets [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset		0		0
Other Postretirement Benefits | Mutual Funds [Member] | U.S. Equities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset		(87.7)		(91.3)
Other Postretirement Benefits | Mutual Funds [Member] | U.S. Equities [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset		(87.7)		(91.3)
Other Postretirement Benefits | Mutual Funds [Member] | U.S. Equities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset		0		0
Other Postretirement Benefits | Mutual Funds [Member] | U.S. Equities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset		0		0
Other Postretirement Benefits | Mutual Funds [Member] | International Equities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset		(42.8)		(41.2)
Other Postretirement Benefits | Mutual Funds [Member] | International Equities [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset		(42.8)		(41.2)
Other Postretirement Benefits | Mutual Funds [Member] | International Equities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset		0		0
Other Postretirement Benefits | Mutual Funds [Member] | International Equities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset		0		0
Other Postretirement Benefits | Mutual Funds [Member] | Fixed Income [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset		(76.5)		(76.2)
Other Postretirement Benefits | Mutual Funds [Member] | Fixed Income [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset		(76.5)		(76.2)
Other Postretirement Benefits | Mutual Funds [Member] | Fixed Income [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset		0		0
Other Postretirement Benefits | Mutual Funds [Member] | Fixed Income [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of asset		$ 0		$ 0
[1]	This class represents pending trades with brokers.
[2]	This class represents pending trades with brokers.
[3]	This class includes limited partnerships/fund of funds that invest in a diverse portfolio of private equity strategies, including buy-outs, venture capital, growth capital, special situations and secondary markets, primarily in the United States.
[4]	This class includes limited partnerships/fund of funds that invest in a diverse portfolio of private equity strategies, including buy-outs, venture capital, growth capital, special situations and secondary markets, primarily outside the United States.

Pension And Other Postretirem90

Pension And Other Postretirement Benefits (Schedule Of Changes In The Fair Value Of The Plan Level Three Assets) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at beginning of year		$ 574.8
Fair value of plan assets at end of year		586	$ 574.8
Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at beginning of year		17.6	18.9
Total gains or losses (unrealized / realized)		0	0.7
Purchases		0	0.6
(Sales)		0	(2.6)
Transfers into/(out of) level 3		0	0
Fair value of plan assets at end of year		0	17.6
Defined Benefit Plan, Separation Allocation	[1]	(17.6)
Real Estate [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at beginning of year		2.6	3
Total gains or losses (unrealized / realized)			0.3
Purchases			0
(Sales)			(0.7)
Transfers into/(out of) level 3			0
Fair value of plan assets at end of year			2.6
Private Equity Limited Partnerships [Member] | U.S. Multi-Strategy [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at beginning of year		8.5	8.7
Total gains or losses (unrealized / realized)		0	0.4
Purchases		0	0.4
(Sales)		0	(1)
Transfers into/(out of) level 3		0	0
Fair value of plan assets at end of year		0	8.5
Defined Benefit Plan, Separation Allocation	[1]	(8.5)
Private Equity Limited Partnerships [Member] | International Multi-Strategy [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at beginning of year		5.3	5.8
Total gains or losses (unrealized / realized)		0	(0.1)
Purchases		0	0.1
(Sales)		0	(0.5)
Transfers into/(out of) level 3		0	0
Fair value of plan assets at end of year		0	5.3
Defined Benefit Plan, Separation Allocation	[1]	(5.3)
Private Equity Limited Partnerships [Member] | Distressed Opportunities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at beginning of year		1.1	1.4
Total gains or losses (unrealized / realized)		0	0.1
Purchases		0	0
(Sales)		0	(0.4)
Transfers into/(out of) level 3		0	0
Fair value of plan assets at end of year		0	1.1
Defined Benefit Plan, Separation Allocation	[1]	(1.1)
Private Equity Limited Partnerships [Member] | Real Estate [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at beginning of year		2.6
Total gains or losses (unrealized / realized)		0
Purchases		0
(Sales)		0
Transfers into/(out of) level 3		0
Fair value of plan assets at end of year		0	2.6
Defined Benefit Plan, Separation Allocation	[1]	(2.6)
Fixed Income Securities [Member] | Other Fixed Income [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at beginning of year		0.1	0
Total gains or losses (unrealized / realized)		0	0
Purchases		0	0.1
(Sales)		0	0
Transfers into/(out of) level 3		0	0
Fair value of plan assets at end of year		0	$ 0.1
Defined Benefit Plan, Separation Allocation	[1]	$ (0.1)
[1]	Level 3 assets were not contributed to the CPG Plans upon Separation from NiSource and no subsequent investments were made in Level 3 assets post Separation.

Pension And Other Postretirem91

Pension And Other Postretirement Benefits (Schedule Of Reconciliation Of The Plans Funded Status And Amounts Reflected) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015		Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at beginning of year		$ 574.8
Fair value of plan assets at end of year		586		$ 574.8
Postretirement and postemployment benefits assets		115.7		90
Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation at beginning of year	[1]	397.6		376.7
Service cost	[1]	5.9		4.8
Interest cost	[1]	15		15.7
Plan participants' contributions	[1]	0		0
Actuarial loss (gain)	[1]	(6.9)		22.7
Benefits paid	[1]	(29.7)		(22.3)
Transfer of Participant Balances, Plan Assets	[2]	15.3		0
Estimated benefits paid by incurred subsidy	[1]	0		0
Transfer of Participant Balances from NiSource Plans	[1],[2]	22.6		0
Projected benefit obligation at end of year	[1]	404.5		397.6
Fair value of plan assets at beginning of year		351		344.5
Actual return on plan assets		1.2		21.1
Employer contributions		20		7.7
Fair value of plan assets at end of year		357.8		351
Funded Status at end of year		(46.7)		(46.6)
Postretirement and postemployment benefits assets		0		0
Current liabilities		(0.8)		0
Noncurrent liabilities		(45.9)		(46.6)
Net amount recognized at end of year	[3]	(46.7)		(46.6)
Unrecognized prior service cost	[4]	(3.7)		(4.7)
Unrecognized actuarial loss	[4]	164.5		148.7
Defined Benefit Plan Amounts Recognized In Other Comprehensive Income Or Regulatory Asset Or Liability	[4]	160.8		144
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation at beginning of year	[1]	124.2		120.9
Service cost	[1]	1		1.1
Interest cost		4.7	[1]	4.6
Defined Benefit Plan, Interest Cost 1	[1]			5.2
Plan participants' contributions	[1]	2.3		3
Actuarial loss (gain)	[1]	(12.4)		5.7
Benefits paid	[1]	(9.8)		(12.4)
Transfer of Participant Balances, Plan Assets	[2]	0.9		0
Estimated benefits paid by incurred subsidy	[1]	0.3		0.7
Transfer of Participant Balances from NiSource Plans	[1],[2]	1.8		0
Projected benefit obligation at end of year	[1]	112.1		124.2
Fair value of plan assets at beginning of year		223.8		209.7
Actual return on plan assets		(2.5)		11.6
Employer contributions		13.5		11.9
Fair value of plan assets at end of year		228.2		223.8
Funded Status at end of year		116.1		99.6
Postretirement and postemployment benefits assets		116.1		113.1
Current liabilities		0		0
Noncurrent liabilities		0		(13.5)
Net amount recognized at end of year	[3]	116.1		99.6
Unrecognized prior service cost	[4]	(2)		(2.6)
Unrecognized actuarial loss	[4]	(3.9)		(12.5)
Defined Benefit Plan Amounts Recognized In Other Comprehensive Income Or Regulatory Asset Or Liability	[4]	$ (5.9)		$ (15.1)
[1]	The change in benefit obligation for Pension Benefits represents the change in Projected Benefit Obligation while the change in benefit obligation for Other Postretirement Benefits represents the change in Accumulated Postretirement Benefit Obligation.
[2]	Reflects the transfer of additional pension and OPEB plan participants to CPGSC upon Separation from NiSource that were determined in the current year.
[3]	CPG recognizes in its Consolidated Balance Sheets the underfunded and overfunded status of its various defined benefit postretirement plans, measured as the difference between the fair value of the plan assets and the benefit obligation.
[4]	CPG determined that the future recovery of pension and other postretirement benefits costs is probable. CPG recorded regulatory assets and liabilities of $135.2 million and $0.7 million, respectively, as of December 31, 2015, and $120.9 million and $8.3 million, respectively, as of December 31, 2014 that would otherwise have been recorded to accumulated other comprehensive loss.

Pension And Other Postretirem92

Pension And Other Postretirement Benefits (Schedule Of Significant Actuarial Assumptions In Determining Funded Status Plan) (Details)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Discount Rate	4.05%	3.64%
Rate of Compensation Increases	4.00%	4.00%
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Discount Rate	4.29%	3.96%
Trend for Next Year	8.39%	6.90%
Ultimate Trend	4.50%	4.50%
Year Ultimate Trend Reached	2,022	2,021

Pension And Other Postretirem93

Pension And Other Postretirement Benefits (Schedule Of One-Percentage-Point Change In Assumed Health Care Cost Trend Rates) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2015USD ($)
Defined Benefit Plan Disclosure [Line Items]
Effect on service and interest components of net periodic cost, 1% point increase	$ 0.1
Effect on service and interest components of net periodic cost, 1% point decrease	(0.1)
Effect on accumulated postretirement benefit obligation, 1% point increase	3.1
Effect on accumulated postretirement benefit obligation, 1% point decrease	$ (2.8)

Pension And Other Postretirem94

Pension And Other Postretirement Benefits (Schedule Of Expected Payments To Participants In Pension Plan) (Details) $ in Millions	Dec. 31, 2015USD ($)
Pension Plan
Defined Benefit Plan Disclosure [Line Items]
2,016	$ 34.9
2,017	33.9
2,018	35.1
2,019	35.8
2,020	37.1
2021-2025	175.3
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
2,016	8.2
2,017	8
2,018	8
2,019	7.9
2,020	7.9
2021-2025	37.4
Postretirement Health Coverage [Member]
Defined Benefit Plan Disclosure [Line Items]
2,016	0.6
2,017	0.6
2,018	0.6
2,019	0.6
2,020	0.5
2021-2025	$ 1.7

Pension And Other Postretirem95

Pension And Other Postretirement Benefits (Components Of The Plans' Net Periodic Benefits Cost) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015		Dec. 31, 2014	Dec. 31, 2013
Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Service Cost	[1]	$ 5.9		$ 4.8
Interest cost	[1]	15		15.7
Expected return on assets		(28.2)		(27.3)
Amortization of prior service cost		(1.1)		(1.1)
Recognized actuarial loss		9.9		7.5
Net Periodic Benefit Costs		1.5		(0.4)
Settlement loss		0		0
Total Net Periodic Benefits Cost		1.5		(0.4)
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Service Cost	[1]	1		1.1
Interest cost		4.7	[1]	4.6
Expected return on assets		(18.1)		(16.6)
Amortization of prior service cost		(0.3)		0.1
Recognized actuarial loss		(0.3)		0
Net Periodic Benefit Costs		(13)		(10.8)
Settlement loss		0		0
Total Net Periodic Benefits Cost		$ (13)		$ (10.8)
Predecessor | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Service Cost					$ 4.9
Interest cost					14.6
Expected return on assets					(25.5)
Amortization of prior service cost					(1.1)
Recognized actuarial loss					12.3
Net Periodic Benefit Costs					5.2
Settlement loss					13.8
Total Net Periodic Benefits Cost					19
Predecessor | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Service Cost					1.5
Interest cost					5.4
Expected return on assets					(13.8)
Amortization of prior service cost					0.1
Recognized actuarial loss					1
Net Periodic Benefit Costs					(5.8)
Settlement loss					0
Total Net Periodic Benefits Cost					$ (5.8)
[1]	The change in benefit obligation for Pension Benefits represents the change in Projected Benefit Obligation while the change in benefit obligation for Other Postretirement Benefits represents the change in Accumulated Postretirement Benefit Obligation.

Pension And Other Postretirem96

Pension And Other Postretirement Benefits (Schedule Of Key Assumptions That Were Used To Calculate The Net Periodic Benefits Cost) (Details)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Discount Rate	3.84%	4.34%
Expected Long-Term Rate of Return on Plan Assets	8.20%	8.30%
Rate of Compensation Increases	4.00%	4.00%
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Discount Rate	4.10%	4.76%
Expected Long-Term Rate of Return on Plan Assets	8.05%	8.14%
Predecessor | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Discount Rate			3.36%
Expected Long-Term Rate of Return on Plan Assets			8.30%
Rate of Compensation Increases			4.00%
Predecessor | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Discount Rate			3.92%
Expected Long-Term Rate of Return on Plan Assets			8.17%

Pension And Other Postretirem97

Pension And Other Postretirement Benefits (Schedule Of Changes In Plan Assets And Projected Benefit Obligations Recognized In Other Comprehensive Income) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014
Pension Plan
Net actuarial (gain)/loss	[1]	$ 6.9	$ (22.7)
Amortization of prior service cost		1.1	1.1
Less: amortization of net actuarial (gain) loss		9.9	7.5
Other Postretirement Benefits
Net actuarial (gain)/loss	[1]	12.4	(5.7)
Amortization of prior service cost		0.3	(0.1)
Less: amortization of net actuarial (gain) loss		(0.3)	0
Other Comprehensive Income Or Regulatory Assets Or Liabilities | Pension Plan
Net actuarial (gain)/loss		25.6	28.9
Amortization of prior service cost		(1.1)	(1.1)
Less: amortization of net actuarial (gain) loss		(9.9)	(7.5)
Total Recognized in Other Comprehensive Income or Regulatory Asset or Liability		16.8	22.5
Amount Recognized in Net Periodic Benefits Cost and Other Comprehensive Income or Regulatory Asset or Liability		18.3	22.1
Other Comprehensive Income Or Regulatory Assets Or Liabilities | Other Postretirement Benefits
Net actuarial (gain)/loss		8.6	11.8
Amortization of prior service cost		(0.3)	0.1
Less: amortization of net actuarial (gain) loss		0.3	0
Total Recognized in Other Comprehensive Income or Regulatory Asset or Liability		9.2	11.7
Amount Recognized in Net Periodic Benefits Cost and Other Comprehensive Income or Regulatory Asset or Liability		$ (3.8)	$ 0.9
[1]	The change in benefit obligation for Pension Benefits represents the change in Projected Benefit Obligation while the change in benefit obligation for Other Postretirement Benefits represents the change in Accumulated Postretirement Benefit Obligation.

Fair Value (Carrying Amount And

Fair Value (Carrying Amount And Estimated Fair Values Of Financial Instruments) (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Fair Value Disclosures [Abstract]
Current portion of long-term debt-affiliated, Carrying Amount	$ 0	$ 115.9
Current Portion of Long Term Debt- affiliated, Fair Value	0	120
Long-term debt	2,746.2	0
Long-term debt, Estimated Fair Value	2,592.1	0
Long-term debt-affiliated	0	1,472.8
Long-term debt-affiliated, Estimated Fair Value	$ 0	$ 1,550.4

Authorized Preferred Stock (Det

Authorized Preferred Stock (Details)	Dec. 31, 2015$ / sharesshares
Equity [Abstract]
Preferred Stock, Shares Authorized	80,000,000
Preferred Stock, Par or Stated Value Per Share | $ / shares	$ 0.01
Preferred Stock, Shares Outstanding	0

Common Stock Common Stock (Narr

Common Stock Common Stock (Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions	Jan. 29, 2016	Dec. 07, 2015	Aug. 20, 2015	Aug. 04, 2015	Dec. 31, 2015	Dec. 31, 2014
Class of Stock [Line Items]
Common Stock, Shares Authorized					2,000,000,000
Common Stock, Par or Stated Value Per Share					$ 0.01
Issuance of common stock, net of offering costs		82,225,000			1,394,700,000
Shares Issued Pursuant to Exercise of Over Allotment Option		10,725,000
Proceeds from Issuance of Common Stock					$ 1,394.7	$ 0
Payments for Underwriting Expense					$ 44.2
Common Stock, Dividends, Per Share, Cash Paid			$ 0.125		$ 0.25
Common Stock, Dividends, Per Share, Declared				$ 0.125	$ 0.25	$ 0
Dividends Payable, Date to be Paid				Nov. 20, 2015
Dividends Payable, Date of Record				Oct. 30, 2015
Subsequent Event
Class of Stock [Line Items]
Common Stock, Dividends, Per Share, Declared	$ 0.12875
Dividends Payable, Date to be Paid	Feb. 19, 2016
Dividends Payable, Date of Record	Feb. 8, 2016

Share-Based Compensation (Narra

Share-Based Compensation (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
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	5,513,260
Stock-based employee compensation expense	$ 7.9	$ 4.4	$ 1.1
Related tax benefits	2.9	1.6	0.4
Unrecognized compensation cost related to nonvested awards	$ 21
Weighted-average remaining requisite service period, years	2 years
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term	1 year 2 months
401(k) match, profit sharing and non-elective expense	$ 9.8	$ 8.4	$ 6.1
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted	161,504	586,219	874,182
Fair value of shares granted	$ 4.5	$ 11.3	$ 11.6
Shares nonvested	161,504	1,460,401
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted	580,267	198,532	31,655
Fair value of shares granted		$ 4.2	$ 0.5
Shares vesting period, (years)	3 years
Shares nonvested	2,268,792	230,187
Omnibus Plan | Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Units issued	52,035
Director Plan | Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Units issued	226,908
2014 Award | Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares nonvested	586,219
2014 Award | Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares nonvested	198,532
2013 Award | Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares nonvested	874,182
2013 Award | Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares nonvested	30,087
2015 Award | Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares nonvested	161,504
NiSource Plan | Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted	450,107
Fair value of shares granted	$ 11.6
NiSource Plan | Omnibus Plan | Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Units issued	13,495
Units Converted	21,399
NiSource Plan | 2015 Award | Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares nonvested	450,107
CPG Plan | Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted	130,160
Fair value of shares granted	$ 3.6
CPG Plan | Omnibus Plan | Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Units issued	30,636
CPG Plan | 2015 Award | Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares nonvested	129,665

Share-Based Compensation (Sched

Share-Based Compensation (Schedule Of Transactions Of Restricted Stock Unit) (Details) - Restricted Stock - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Nonvested at December 31, 2014	230,187
Nonvested at December 31, 2014, Weighted Average Grant Date Fair Value	$ 20.27
Converted	1,460,401
Converted, Weighted Average Grant Date Fair Value	$ 15.66
Granted	580,267	198,532	31,655
Granted, Weighted Average Grant Date Fair Value	$ 26.29
Forfeited	(495)
Forfeited, Weighted Average Grant Date Fair Value	$ 28.25
Vested	(1,568)
Vested, Weighted Average Grant Date Fair Value	$ 18.24
Nonvested and Expected to Vest at December 31, 2015	2,268,792	230,187
Nonvested and Expected to Vest at December 31, 2015, Weighted Average Grant Date Fair Value	$ 18.85	$ 20.27

Share-Based Compensation (Sc103

Share-Based Compensation (Schedule Of Transactions Of Contingent Awards) (Details) - Performance Shares [Member] - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Nonvested at December 31, 2014	1,460,401
Nonvested at December 31, 2014, Weighted Average Grant Date Fair Value	$ 15.66
Converted	(1,460,401)
Granted	161,504	586,219	874,182
Granted, Weighted Average Grant Date Fair Value	$ 28.16
Forfeited	0
Forfeited, Weighted Average Grant Date Fair Value	$ 0
Vested	0
Vested, Weighted Average Grant Date Fair Value	$ 0
Nonvested and Expected to Vest at December 31, 2015	161,504	1,460,401
Nonvested and Expected to Vest at December 31, 2015, Weighted Average Grant Date Fair Value	$ 28.16	$ 15.66

Other Commitments And Contin104

Other Commitments And Contingencies (Narrative) (Details) $ in Millions	Oct. 01, 2015	Aug. 18, 2015	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)	Dec. 31, 2013USD ($)	Dec. 05, 2014USD ($)	Aug. 31, 2010USD ($)
Other Commitments And Contingencies [Line Items]
Line of Credit Facility Used For Credit Support for Subsidiaries			$ 750
Line of Credit Facility Used For Corporate Purposes			750
Commercial paper			0	$ 0
Guarantor Obligations, Maximum Exposure, Undiscounted			63.8
Accrual for Environmental Loss Contingencies			8.3	14.3
Liability for estimated remediation costs			6.5	12.5
Ozone Level Maximum	70 ppb
Percentage Reduction in Methane Emissions		95.00%
Hours of Operation		26,000
Replacement Years		3 years
Payments made in connection with operating leases			21.2	14.9	$ 13.3
PCB
Other Commitments And Contingencies [Line Items]
Liability for estimated remediation costs			$ 1.8
Propane
Other Commitments And Contingencies [Line Items]
Number of waste disposal sites identified by program			4
Petroleum
Other Commitments And Contingencies [Line Items]
Number of waste disposal sites identified by program			10
Millennium Pipeline
Other Commitments And Contingencies [Line Items]
Face amount of notes							$ 725
Guarantor Obligations, Maximum Exposure, Undiscounted			$ 16.2
Guarantees, Fair Value Disclosure			$ 1.5
Millennium Pipeline
Other Commitments And Contingencies [Line Items]
Equity Method Investment, Ownership Percentage			47.50%
Guarantee Type, Other
Other Commitments And Contingencies [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted			$ 45.7
Letter of Credit
Other Commitments And Contingencies [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted			18.1
Revolving Credit Facility
Other Commitments And Contingencies [Line Items]
Revolving credit facility, maximum			1,500
Credit facilities borrowings			0	0
Letters of Credit Outstanding, Amount			18.1
Revolving Credit Facility | CPPL
Other Commitments And Contingencies [Line Items]
Revolving credit facility, maximum						$ 500
Credit facilities borrowings			15	$ 0
Letters of Credit Outstanding, Amount			0
Commercial Paper
Other Commitments And Contingencies [Line Items]
Revolving credit facility, maximum			1,000
Letter of Credit
Other Commitments And Contingencies [Line Items]
Revolving credit facility, maximum			250
Letter of Credit | CPPL
Other Commitments And Contingencies [Line Items]
Revolving credit facility, maximum			50
IBM Service Agreement
Other Commitments And Contingencies [Line Items]
Purchase And Service Obligations Minimum Fixed Payments Due			165.3
Senior Notes
Other Commitments And Contingencies [Line Items]
Face amount of notes			$ 2,750

Other Commitments And Contin105

Other Commitments And Contingencies (Existence And Expiration Of Commercial Commitments) (Details) $ in Millions	Dec. 31, 2015USD ($)
Other Commitments And Contingencies [Line Items]
2,016	$ 18.7
2,017	2
2,018	0
2,019	0
2,020	0
Thereafter	43.1
Total	63.8
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	43.1
Total	$ 45.7

Other Commitments And Contin106

Other Commitments And Contingencies (Future Minimum Lease Payments Required Under Operating And Capital Leases) (Details) $ in Millions	Dec. 31, 2015USD ($)	[1]
Unrecorded Unconditional Purchase Obligation [Line Items]
2,016	$ 5.4
2,017	6.7
2,018	6.2
2,019	5.5
2,020	5.4
After	24.7
Total future minimum payments	$ 53.9
[1]	Operating lease expense includes amounts for fleet leases and storage well leases that can be renewed beyond the initial lease term, but the anticipated payments associated with the renewals do not meet the definition of expected minimum lease payments and, therefore, are not included above.

Other Commitments And Contin107

Other Commitments And Contingencies (Estimated Aggregate Amounts Of Minimum Fixed Payments On Purchase And Service Obligations) (Details) $ in Millions	Dec. 31, 2015USD ($)
Pipeline Service Agreements
Other Commitments And Contingencies [Line Items]
Purchase And Service Obligations Minimum Fixed Payments Due Current	$ 51.5
2,016	49.5
2,017	42
2,019	25.4
2,020	24.2
After	66.8
Total future minimum payments	259.4
IBM Service Agreement
Other Commitments And Contingencies [Line Items]
Purchase And Service Obligations Minimum Fixed Payments Due Current	38.6
2,016	33
2,017	31.7
2,019	31
2,020	31
After	0
Total future minimum payments	$ 165.3

Accumulated Other Comprehens108

Accumulated Other Comprehensive Loss (Narrative) (Details) $ in Millions	Aug. 31, 2010USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)	Dec. 31, 2008USD ($)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Number Of Notes Tranches Through Private Placement Issuance		2
Millennium Pipeline
Accumulated Other Comprehensive Income (Loss) [Line Items]
Number of interest rate swap agreements				3
Notional amount of interest rate swap agreements				$ 420
Number of counterparties entered into interest rate swap agreement				7
Refinancing of long-term debt	$ 725
Debt Instrument, Maturity Date		Jun. 1, 2025
Other Comprehensive Income Unrecognized Gain Loss On Derivatives Arising During Period Net Of Tax		$ 14.3	$ 16.6
Unrealized loss, amortization period		15 years
Notes Due 2027 [Member] | Millennium Pipeline
Accumulated Other Comprehensive Income (Loss) [Line Items]
Refinancing of long-term debt	$ 375
Debt Instrument, Interest Rate, Stated Percentage	5.33%
Debt Instrument, Maturity Date	Jun. 30, 2027
Notes Due 2032 | Millennium Pipeline
Accumulated Other Comprehensive Income (Loss) [Line Items]
Refinancing of long-term debt	$ 350
Debt Instrument, Interest Rate, Stated Percentage	6.00%
Debt Instrument, Maturity Date	Jun. 30, 2032

Accumulated Other Comprehens109

Accumulated Other Comprehensive Loss (Components Of Accumulated Other Comprehensive Loss) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	[1]	$ (34.5)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	[1]	4.1	$ (9.3)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	[1]	1.3	0.6
Total Comprehensive Income	[1]	5.4	(8.7)
Ending Balance	[1]	(27)	(34.5)
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	[1]	(16.6)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	[1]	(0.9)	0
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	[1]	1.1	1
Total Comprehensive Income	[1]	0.2	1
Ending Balance	[1]	(14.3)	(16.6)
Accumulated Defined Benefit Plans Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	[1]	(17.9)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	[1]	5	(9.3)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	[1]	0.2	(0.4)
Total Comprehensive Income	[1]	5.2	(9.7)
Ending Balance	[1]	(12.7)	(17.9)
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Noncontrolling Interest [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total Comprehensive Income	[1]	2.1
Accumulated Defined Benefit Plans Adjustment Attributable to Noncontrolling Interest [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total Comprehensive Income	[1]	0
AOCI Attributable to Noncontrolling Interest [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total Comprehensive Income	[1]	$ 2.1
Predecessor
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	[1]		(25.8)	$ (35.1)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	[1]			6.5
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	[1]			2.8
Total Comprehensive Income	[1]			9.3
Ending Balance	[1]			(25.8)
Predecessor | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	[1]		(17.6)	(18.7)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	[1]			0
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	[1]			1.1
Total Comprehensive Income	[1]			1.1
Ending Balance	[1]			(17.6)
Predecessor | Accumulated Defined Benefit Plans Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	[1]		$ (8.2)	(16.4)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	[1]			6.5
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	[1]			1.7
Total Comprehensive Income	[1]			8.2
Ending Balance	[1]			$ (8.2)
[1]	All amounts are net of tax. Amounts in parentheses indicate debits.

Other, Net (Schedule Of Other N

Other, Net (Schedule Of Other Net) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Schedule Of Other, Net [Line Items]
AFUDC Equity		$ 28.3	$ 11
Miscellaneous	[1]	1	(2.2)
Total Other, net		$ 29.3	$ 8.8
Predecessor
Schedule Of Other, Net [Line Items]
AFUDC Equity				$ 6.8
Miscellaneous	[1]			11.1
Total Other, net				$ 17.9
[1]	Miscellaneous primarily consists of a gain from insurance proceeds in 2013.

Interest Expense (Details)

Interest Expense (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014		Dec. 31, 2013
Schedule Of Interest Expense [Line Items]
Interest on long-term debt		$ 67.5	$ 0
Interest on short-term borrowings	[1]	1.4	0
Debt discount/cost amortization		3.1	0
Allowance for funds used during construction		6.8	0
Other		2.4	0
Total Interest Expense		$ 67.6	$ 0	[2]
Predecessor
Schedule Of Interest Expense [Line Items]
Interest on long-term debt					$ 0
Interest on short-term borrowings	[1]				0
Debt discount/cost amortization					0
Allowance for funds used during construction					0
Other					0
Total Interest Expense	[2]				$ 0
[1]	Refer to Note 5, "Short-Term Borrowings" for additional information.
[2]	Refer to Note 4, "Transactions with Affiliates" for a discussion of interest expense-affiliated for the year ended December 31, 2014 and 2013.

Segments Of Business (Narrative

Segments Of Business (Narrative) (Details)	12 Months Ended
	Dec. 31, 2015
Segment Reporting [Abstract]
Number of Reportable Segments	1

Supplemental Cash Flow Infor113

Supplemental Cash Flow Information Supplemental Cash Flow Information (Narrative) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2015USD ($)
Supplemental Cash Flow Elements [Abstract]
Cash Paid for Taxes Under Tax Allocation Agreement	$ 20.9

Supplemental Cash Flow Infor114

Supplemental Cash Flow Information (Schedule of Supplemental Cash Flow Information) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015		Dec. 31, 2014	Dec. 31, 2013
Supplemental Cash Flow [Line Items]
Capital expenditures included in current liabilities	[1]	$ 128.4		$ 78.5
Cash paid for interest, net of interest capitalized amounts		96.9		53.6
Cash paid for income taxes		$ 32.3	[2]	$ 21.2
Predecessor
Supplemental Cash Flow [Line Items]
Capital expenditures included in current liabilities	[1]				$ 53.1
Cash paid for interest, net of interest capitalized amounts					38.4
Cash paid for income taxes					$ 15.3
[1]	Capital expenditures included in current liabilities is comprised of "Accrued capital expenditures" and certain other amounts included within "Accounts payable" on the Consolidated Balance Sheets.
[2]	Cash paid for income taxes for the year ended December 31, 2015 includes $20.9 million paid to NiSource under the Tax Allocation Agreement.

Concentration of Credit Risk (N

Concentration of Credit Risk (Narrative) (Details)	12 Months Ended
	Dec. 31, 2015
Risks and Uncertainties [Abstract]
Concentration Risk, Benchmark Description	greater than 10% of total operating revenues

Concentration of Credit Risk (S

Concentration of Credit Risk (Schedule of Concentration of Credit Risk) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Concentration Risk [Line Items]
Revenues		$ 1,334.9	$ 1,348
Credit Concentration Risk
Concentration Risk [Line Items]
Revenues	[1]	$ 167.3	$ 168.5
Concentration Risk, Percentage	[1]	12.50%	12.50%
Predecessor
Concentration Risk [Line Items]
Revenues				$ 1,180.5
Predecessor | Credit Concentration Risk
Concentration Risk [Line Items]
Revenues	[1]			$ 167.5
Concentration Risk, Percentage	[1]			14.20%
[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 agreements with third parties which ultimately can decrease the net revenue amount CPG receives from Columbia Gas of Ohio in any given period.

Quarterly Financial Data (Un117

Quarterly Financial Data (Unaudited) (Schedule Of Quarterly Financial Data) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								11 Months Ended	12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2015	Dec. 31, 2014
Quarterly Financial Data [Abstract]
Total Operating Revenues	$ 357.9	$ 320.9	$ 316.1	$ 340	$ 340.7	$ 318	$ 343.5	$ 345.8
Operating Income	122.2	135.9	107.3	162.7	134.1	94.5	103.9	159.1		$ 528.1	$ 491.6
Income from Continuing Operations	75.4	74.9	60.1	97.1	62.6	53.7	59.4	93		267.6	268.7
Results from Discontinued Operations-net of taxes	0	(0.1)	(0.3)	0	0	(0.1)	(0.3)	(0.2)		(0.4)	(0.6)
Net Income attributable to CPG	$ 63.4	$ 63	$ 50.8	$ 90	$ 62.6	$ 53.6	$ 59.1	$ 92.8	$ 267.2	$ 267.2	$ 268.1
Basic Earnings Per Share
Continuing Operations	$ 0.19	$ 0.20	$ 0.16	$ 0.28	$ 0.20	$ 0.17	$ 0.19	$ 0.29		$ 0.81	$ 0.84
Discontinued Operations	0	0	0	0	0	0	0	0		0	0
Basic Earnings Per Share	0.19	0.20	0.16	0.28	0.20	0.17	0.19	0.29		0.81	0.84
Diluted Earnings Per Share
Continuing Operations	0.19	0.20	0.16	0.28	0.20	0.17	0.19	0.29		0.81	0.84
Discontinued Operations	0	0	0	0	0	0	0	0		0	0
Diluted Earnings Per Share	$ 0.19	$ 0.20	$ 0.16	$ 0.28	$ 0.20	$ 0.17	$ 0.19	$ 0.29		$ 0.81	$ 0.84