NiSource (NI) 10-Q30 Oct 142014 Q3 Quarterly reportFinancial data

Company Profile

Document_And_Entity_Informatio

Document And Entity Information	9 Months Ended
Document And Entity Information	Sep. 30, 2014	Oct. 23, 2014
Document Information [Line Items]	'	'
Document Type	'10-Q	'
Amendment Flag	'false	'
Document Period End Date	30-Sep-14	'
Document Fiscal Year Focus	'2014	'
Document Fiscal Period Focus	'Q3	'
Entity Registrant Name	'NISOURCE INC/DE	'
Entity Central Index Key	'0001111711	'
Current Fiscal Year End Date	'--12-31	'
Entity Filer Category	'Large Accelerated Filer	'
Entity Common Stock, Shares Outstanding	'	315,699,826

Statements_Of_Consolidated_Inc

Statements Of Consolidated Income (USD $)	3 Months Ended		9 Months Ended
In Millions, except Share data in Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Net Revenues	'	'	'	'
Gas Distribution	$240.30	$255.10	$1,878.80	$1,540.60
Gas Transportation and Storage	381.7	346.9	1,350.30	1,181.90
Electric	424.6	413.4	1,279.40	1,175.20
Other	77.3	61.4	271	162.8
Gross Revenues	1,123.90	1,076.80	4,779.50	4,060.50
Cost of Sales (excluding depreciation and amortization)	230.5	243	1,663.50	1,268.30
Total Net Revenues	893.4	833.8	3,116	2,792.20
Operating Expenses	'	'	'	'
Operation and maintenance	529.5	468.9	1,563.80	1,375.60
Depreciation and amortization	153	144.5	450.8	431.4
Gain on sale of assets, net	-2.9	-9.8	-19.3	-10.2
Other taxes	68	64.3	242.5	221.7
Total Operating Expenses	747.6	667.9	2,237.80	2,018.50
Equity Earnings in Unconsolidated Affiliates	12	10.5	32.9	25.6
Operating Income	157.8	176.4	911.1	799.3
Other Income (Deductions)	'	'	'	'
Interest expense, net	-109.6	-103.7	-327.8	-304.3
Other, net	9.2	4.7	21.2	22.1
Total Other Deductions	-100.4	-99	-306.6	-282.2
Income from Continuing Operations before Income Taxes	57.4	77.4	604.5	517.1
Income Taxes	25.9	27.9	228.1	179.2
Income from Continuing Operations	31.5	49.5	376.4	337.9
(Loss) Income from Discontinued Operations - net of taxes	-0.1	0.1	-0.6	7.5
(Loss) Gain on Disposition of Discontinued Operations - net of taxes	0	-1.5	0	34.9
Net Income	$31.40	$48.10	$375.80	$380.30
Basic Earnings (Loss) Per Share ($)	'	'	'	'
Continuing Operations	$0.10	$0.16	$1.19	$1.08
Discontinued operations	$0	$0	$0	$0.14
Basic Earnings Per Share	$0.10	$0.16	$1.19	$1.22
Diluted Earnings (Loss) Per Share ($)	'	'	'	'
Continuing operations	$0.10	$0.16	$1.19	$1.08
Discontinued operations	$0	$0	$0	$0.14
Earnings Per Share, Diluted	$0.10	$0.16	$1.19	$1.22
Dividends Declared Per Common Share	$0.26	$0.25	$1.02	$0.98
Basic Average Common Shares Outstanding	315,418	312,842	314,889	312,053
Diluted Average Common Shares	316,626	313,813	316,006	312,959

Statements_of_Consolidated_Com

Statements of Consolidated Comprehensive Income (USD $)	3 Months Ended				9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013
Net Income	$31.40		$48.10		$375.80		$380.30
Net unrealized (loss) gain on available-for-sale securities	-0.6	[1]	0.9	[1]	0.2	[1]	-2.4	[1]
Net unrealized gain on cash flow hedges	0.6	[2]	0.6	[2]	1.9	[2]	2	[2]
Unrecognized pension and OPEB (cost) benefit	-0.2	[3]	0.1	[3]	-0.1	[3]	5.5	[3]
Total other comprehensive (loss) income	-0.2		1.6		2		5.1
Total Comprehensive Income	$31.20		$49.70		$377.80		$385.40

[1]	Net unrealized (loss) gain on available-for-sale securities, net of $0.3 million tax benefit and $0.5 million tax expense in the third quarter of 2014 and 2013, respectively, and $0.1 million tax expense and $1.3 million tax benefit for the nine months ended 2014 and 2013, respectively.
[2]	Net unrealized gains on derivatives qualifying as cash flow hedges, net of $0.4 million tax expense in the third quarter of 2014 and 2013, and $1.2 million and $1.3 million tax expense for the nine months ended 2014 and 2013, respectively.
[3]	Unrecognized pension and OPEB (cost) benefit, net of zero tax benefit and tax expense in the third quarter of 2014 and 2013, respectively, and $0.7 million tax benefit and $3.5 million tax expense for the nine months ended 2014 and 2013, respectively.

Statements_of_Consolidated_Com1

Statements of Consolidated Comprehensive Income (Parenthetical) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Tax	($0.30)	$0.50	$0.10	($1.30)
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Tax	0.4	0.4	1.2	1.3
Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Tax	$0	$0	$0.70	($3.50)

Statements_of_Consolidated_Bal

Statements of Consolidated Balance Sheets (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Millions, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Property, Plant and Equipment	'	'
Utility Plant	$24,775.70	$23,303.70
Accumulated depreciation and amortization	-9,533.20	-9,256.50
Net utility plant	15,242.50	14,047.20
Other property, at cost, less accumulated depreciation	344	317.9
Net Property, Plant and Equipment	15,586.50	14,365.10
Investments and Other Assets	'	'
Unconsolidated affiliates	443.5	373.7
Other investments	211.7	204
Total Investments and Other Assets	655.2	577.7
Current Assets	'	'
Cash and cash equivalents	17.7	26.8
Restricted Cash	16	8
Accounts receivable (less reserve of $18.4 and $23.5, respectively)	639.3	1,005.80
Gas inventory	513	354.6
Underrecovered gas and fuel costs	54.7	46.4
Materials and supplies, at average cost	106.4	101.2
Electric production fuel, at average cost	48.2	44.6
Exchange gas receivable	80.9	70.6
Regulatory assets	200.1	142.8
Deferred Tax Assets, Net, Current	231.7	175.3
Prepayments and other	103.6	183.1
Total Current Assets	2,011.60	2,159.20
Other Assets	'	'
Regulatory assets	1,440.90	1,522.20
Goodwill	3,666.20	3,666.20
Intangible assets	267.4	275.7
Deferred charges and other	82.3	87.8
Total Other Assets	5,456.80	5,551.90
Total Assets	23,710.10	22,653.90
Common Stockholders' Equity	'	'
Common stock - $0.01 par value, 400,000,000 shares authorized; 315,597,089 and 313,675,911 shares outstanding, respectively	3.2	3.2
Additional paid-in capital	4,764.70	4,690.10
Retained earnings	1,339.90	1,285.50
Accumulated other comprehensive loss	-41.6	-43.6
Treasury stock	-58.9	-48.6
Total Common Stockholders' Equity	6,007.30	5,886.60
Long-term debt, excluding amounts due within one year	8,397.40	7,593.20
Total Capitalization	14,404.70	13,479.80
Current Liabilities	'	'
Current portion of long-term debt	18.7	542.1
Short-term borrowings	1,311.10	698.7
Accounts payable	427.7	619
Dividends payable	82.1	0
Customer deposits and credits	257.1	262.6
Taxes accrued	189.3	254.8
Interest accrued	81.7	136.4
Overrecovered gas and fuel costs	21.2	32.2
Exchange gas payable	143.1	186.4
Deferred revenue	6.5	18.5
Regulatory liabilities	79.9	60.2
Accrued liability for postretirement and postemployment benefits	6.2	6.2
Legal and environmental	15.3	32.3
Other accruals	408.6	329
Total Current Liabilities	3,048.50	3,178.40
Other Liabilities and Deferred Credits	'	'
Deferred income taxes	3,540.80	3,277.80
Deferred investment tax credits	18.2	20.9
Deferred credits	102.7	91.9
Deferred revenue	20.9	17.1
Accrued liability for postretirement and postemployment benefits	425.6	527.5
Regulatory liabilities	1,675.80	1,669.80
Asset retirement obligations	175.2	174.4
Other noncurrent liabilities	297.7	216.3
Total Other Liabilities and Deferred Credits	6,256.90	5,995.70
Commitments and Contingencies	0	0
Total Capitalization and Liabilities	$23,710.10	$22,653.90

Statements_of_Consolidated_Bal1

Statements of Consolidated Balance Sheets (Parenthetical) (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Millions, except Share data, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Statement of Financial Position [Abstract]	'	'
Accounts receivable less reserve	$18.40	$23.50
Common stock, par value	$0.01	$0.01
Common stock, shares authorized	400,000,000	400,000,000
Common Stock, Shares, Outstanding	315,597,089	313,675,911

Statements_Of_Consolidated_Cas

Statements Of Consolidated Cash Flows (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013
Operating Activities	'	'
Net Income	$375.80	$380.30
Adjustments to Reconcile Net Income to Net Cash from Continuing Operations:	'	'
Depreciation and amortization	450.8	431.4
Net changes in price risk management assets and liabilities	1.9	1.9
Deferred income taxes and investment tax credits	220.8	199.1
Deferred revenue	1.9	1.6
Stock compensation expense and 401(k) profit sharing contribution	54.6	39.7
Gain on sale of assets	-19.3	-10.2
Income from unconsolidated affiliates	-32.3	-25.5
Gain on disposition of discontinued operations - net of taxes	0	-34.9
Loss (Income) from discontinued operations - net of taxes	0.6	-7.5
Amortization of debt related costs	7.5	7
AFUDC equity	-15.6	-12.7
Distributions of earnings received from equity investees	27.6	19
Changes in Assets and Liabilities:	'	'
Accounts receivable	362.6	318.4
Income tax receivable	2.1	124.6
Inventories	-170.8	-103.7
Accounts payable	-218.1	-177.7
Customer deposits and credits	70.2	-20.4
Taxes accrued	-67.7	-68
Interest accrued	-54.6	-62.1
(Under) Overrecovered gas and fuel costs	-19.2	38.1
Exchange gas receivable/payable	-53.6	28.1
Other accruals	-29.7	-36.5
Prepayments and other current assets	56.1	45.5
Regulatory assets/liabilities	17.1	71.5
Postretirement and postemployment benefits	-102.5	-95.9
Deferred credits	13.8	11.1
Deferred charges and other noncurrent assets	1.5	11.8
Other noncurrent liabilities	6.3	-6.3
Net Operating Activities from Continuing Operations	887.8	1,067.70
Net Operating Activities (used for) from Discontinued Operations	-1.3	10.9
Net Cash Flows from Operating Activities	886.5	1,078.60
Investing Activities	'	'
Capital expenditures	-1,441.70	-1,297.30
Insurance recoveries	6.8	6.4
Proceeds from disposition of assets	7.6	17.9
Restricted cash (deposits) withdrawals	-8.1	28.5
Contributions to equity investees	-63.8	-77.1
Other investing activities	-13	-48.4
Net Investing Activities used for Continuing Operations	-1,512.20	-1,370
Net Investing Activities from Discontinued Operations	0	118.7
Net Cash Flows used for Investing Activities	-1,512.20	-1,251.30
Financing Activities	'	'
Issuance of long-term debt	748.4	815.3
Repayments of long-term debt and capital lease obligations	-517.1	-505.2
Premiums and other debt related costs	0	-3.2
Change in short-term borrowings, net	612.4	43.9
Issuance of common stock	22.4	36.1
Acquisition of treasury stock	-10.3	-8
Dividends paid - common stock	-239.2	-227.6
Net Cash Flows from (used for) Financing Activities	616.6	151.3
Change in cash and cash equivalents used for continuing operations	-7.8	-151
Cash contributions (to) from discontinued operations	-1.3	129.6
Cash and cash equivalents at beginning of period	26.8	36.3
Cash and Cash Equivalents at End of Period	$17.70	$14.90

Recovered_Sheet1

Statements Of Consolidated Common Stockholders' Equity (USD $)	Total	Common Stock [Member]	Treasury Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
In Millions	Total	Common Stock [Member]	Treasury Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Beginning Balance at Dec. 31, 2013	$5,886.60	$3.20	($48.60)	$4,690.10	$1,285.50	($43.60)
Net Income	375.8	0	0	0	375.8	0
Other comprehensive income, net of tax	2	0	0	0	0	2
Common stock dividends	-321.4	0	0	0	-321.4	0
Treasury stock acquired	-10.3	0	-10.3	0	0	0
Employee stock purchase plan	3	0	0	3	0	0
Long-term incentive plan	31.9	0	0	31.9	0	0
401(k) and profit sharing issuance	33.8	0	0	33.8	0	0
Dividend reinvestment plan	5.9	0	0	5.9	0	0
Ending Balance at Sep. 30, 2014	$6,007.30	$3.20	($58.90)	$4,764.70	$1,339.90	($41.60)

Basis_of_Accounting_Presentati

Basis of Accounting Presentation	9 Months Ended
Basis of Accounting Presentation	Sep. 30, 2014
Organization, Consolidation and Presentation of Financial Statements [Abstract]	'
Basis of Accounting Presentation	'
	Basis of Accounting Presentation

	The accompanying Condensed Consolidated Financial Statements (unaudited) for NiSource (the “Company”) reflect all normal recurring adjustments that are necessary, in the opinion of management, to present fairly the results of operations in accordance with GAAP in the United States of America.
	The accompanying financial statements should be read in conjunction with the consolidated financial statements and notes thereto included in NiSource’s Annual Report on Form 10-K for the fiscal year ended December 31, 2013. Income for interim periods may not be indicative of results for the calendar year due to weather variations and other factors.

	The Condensed Consolidated Financial Statements (unaudited) have been prepared pursuant to the rules and regulations of the SEC. Certain information and note disclosures normally included in annual financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to those rules and regulations, although NiSource believes that the disclosures made are adequate to make the information not misleading.

	Planned Separation of Columbia Pipeline Group and Initial Public Offering of Columbia Pipeline Partners LP
	On September 28, 2014, NiSource announced that its Board of Directors had approved in principle plans to separate its natural gas pipeline and related businesses into a stand-alone publicly traded company (the “Proposed Separation”). If completed, the Proposed Separation will result in two energy infrastructure companies: NiSource Inc., a fully regulated natural gas and electric utilities company, and Columbia Pipeline Group Inc., a natural gas pipeline, midstream and storage company (“CPG”). The Proposed Separation is expected to occur in mid-2015.
	Under the plan for the Proposed Separation, NiSource shareholders would retain their current shares of NiSource stock and receive a pro rata distribution of shares of CPG stock in a transaction that is expected to be tax-free to NiSource and its shareholders.
	On September 29, 2014, Columbia Pipeline Partners LP, a wholly owned subsidiary (“CPPL”), filed with the Securities and Exchange Commission a Registration Statement on Form S-1 related to CPPL’s proposed initial public offering of common units representing limited partner interests in CPPL. We expect that CPPL will sell a minority share of its total limited partner interests in the offering, which is expected to occur in the first quarter of 2015. If the proposed offering closes, CPPL’s initial asset would consist of an approximate 14.6% ownership interest in CPG OpCo LP (“Columbia OpCo”), which is the entity that will own substantially all of NiSource’s natural gas transmission, midstream and storage assets. In addition, NiSource, through its ownership of CPG, would indirectly own (a) the remaining ownership interest in Columbia OpCo, (b) the general partner of CPPL, (c) the remaining CPPL limited partner interests that are not sold in the offering and (d) all the incentive distribution rights in CPPL.

Recent_Accounting_Pronouncemen

Recent Accounting Pronouncements	9 Months Ended
Recent Accounting Pronouncements	Sep. 30, 2014
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]	'
Recent Accounting Pronouncements	'
	Recent Accounting Pronouncements

	In June 2014, the FASB issued ASU 2014-12, Compensation - Stock Compensation (Topic 718): Accounting for Share-Based Payments When the Terms of an Award Provide That a Performance Target Could Be Achieved after the Requisite Service Period. ASU 2014-12 clarifies that entities should treat performance targets that can be met after the requisite service period of a share-based payment award as performance conditions that affect vesting. NiSource is required to adopt ASU 2014-12 for periods beginning after December 15, 2015, including interim periods, and the guidance is to be applied prospectively, with early adoption permitted. Retroactive application would apply to awards with performance targets outstanding after the beginning of the first annual period presented. The adoption of this guidance will not have a material impact on the Condensed Consolidated Financial Statements (unaudited) or Notes to Condensed Consolidated Financial Statements (unaudited).
	In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers (Topic 606). ASU 2014-09 outlines a single, comprehensive model for entities to use in accounting for revenue arising from contracts with customers and supersedes most current revenue recognition guidance. The core principle of the new standard is that an entity should recognize revenue to depict the transfer of goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. NiSource is required to adopt ASU 2014-09 for periods beginning after December 15, 2016, including interim periods, and the new standard is to be applied retrospectively with early adoption not permitted. NiSource is currently evaluating the impact the adoption of ASU 2014-09 will have on its Condensed Consolidated Financial Statements (unaudited) and Notes to Condensed Consolidated Financial Statements (unaudited).
	In April 2014, the FASB issued ASU 2014-08, Presentation of Financial Statements (Topic 205) and Property, Plant, and Equipment (Topic 360): Reporting Discontinued Operations and Disclosures of Disposals of Components of an Entity. ASU 2014-08 changes the criteria for reporting a discontinued operation. Under the new pronouncement, a disposal of a part of an organization that has a major effect on its operations and financial results is a discontinued operation. NiSource is required to adopt ASU 2014-08 prospectively for all disposals or components of its business classified as held for sale during fiscal periods beginning after December 15, 2014. NiSource is currently evaluating what impact, if any, adoption of ASU 2014-08 will have on its Condensed Consolidated Financial Statements (unaudited) and Notes to Condensed Consolidated Financial Statements (unaudited).

Earnings_Per_Share

Earnings Per Share	9 Months Ended
	Sep. 30, 2014
Earnings Per Share [Abstract]	'
Earnings Per Share	'
	Earnings Per Share

	Basic EPS is computed by dividing income available to common stockholders by the weighted-average number of shares of common stock outstanding for the period. The weighted average shares outstanding for diluted EPS includes the incremental effects of the various long-term incentive compensation plans. The numerator in calculating both basic and diluted EPS for each period is reported net income. The computation of diluted average common shares follows:



		Three Months Ended		Nine Months Ended September 30,
		September 30,
	(in thousands)	2014	2013	2014	2013
	Denominator
	Basic average common shares outstanding	315,418	312,842	314,889	312,053

	Dilutive potential common shares:
	Stock options	32	112	30	102

	Shares contingently issuable under employee stock plans	725	369	649	327

	Shares restricted under stock plans	451	490	438	477

	Diluted Average Common Shares	316,626	313,813	316,006	312,959

Discontinued_Operations_And_As

Discontinued Operations And Assets And Liabilities Held For Sale	9 Months Ended
	Sep. 30, 2014
Discontinued Operations And Assets And Liabilities Held For Sale [Abstract]	'
Discontinued Operations And Assets And Liabilities Held For Sale	'
	Discontinued Operations and Assets and Liabilities Held for Sale

	There were no assets and liabilities of discontinued operations and held for sale on the Condensed Consolidated Balance Sheets (unaudited) at September 30, 2014 and December 31, 2013.



	Results from discontinued operations are provided in the following table. These results are primarily from a settlement at NiSource's former exploration and production subsidiary, CER, NiSource's Retail Services business, and NiSource's unregulated natural gas marketing business.


		Three Months Ended						Nine Months Ended September 30,
		September 30,
	(in millions)	2014			2013			2014			2013
	Net Revenues from Discontinued Operations	$	—		$	0.4		$	—		$	1.3

	(Loss) Income from discontinued operations	(0.2		)	0.1			(1.0		)	12.2

	Income tax (benefit) expense	(0.1		)	—			(0.4		)	4.7

	(Loss) Income from Discontinued Operations - net of taxes	$	(0.1	)	$	0.1		$	(0.6	)	$	7.5

	(Loss) Gain on Disposition of Discontinued Operations - net of taxes	$	—		$	(1.5	)	$	—		$	34.9

Asset_Retirement_Obligations

Asset Retirement Obligations	9 Months Ended
	Sep. 30, 2014
Asset Retirement Obligation [Abstract]	'
Asset Retirement Obligations	'
	Asset Retirement Obligations
	Certain costs of removal that have been, and continue to be, included in depreciation rates and collected in the service rates of the rate-regulated subsidiaries are classified as “Regulatory liabilities” on the Condensed Consolidated Balance Sheets (unaudited).

	Changes in NiSource’s liability for asset retirement obligations for the nine months ended September 30, 2014 and 2013 are presented in the table below:



	(in millions)	2014			2013
	Balance as of January 1,	$	174.4		$	160.4

	Accretion expense	1.2			0.9

	Accretion recorded as a regulatory asset/liability	6.3			6.5

	Additions	2.3			9.7

	Settlements	(1.4		)	(1.3		)
	Change in estimated cash flows(1)	(7.6		)	(0.7		)
	Balance as of September 30,	$	175.2		$	175.5

	(1)The change in estimated cash flows for 2014 is primarily attributed to changes in estimated costs to retire pipeline.

Regulatory_Matters

Regulatory Matters	9 Months Ended
Regulatory Matters	Sep. 30, 2014
Regulatory Assets and Liabilities Disclosure [Abstract]	'
Regulatory Matters	'
	Regulatory Matters
	Gas Distribution Operations Regulatory Matters

	Significant Rate Developments. On April 30, 2013, Indiana Governor Pence signed Senate Enrolled Act 560 into law. Among other provisions, this legislation provides for cost recovery outside of a base rate proceeding for new or replacement electric and gas transmission, distribution, and storage projects that a public utility undertakes for the purposes of safety, reliability, system modernization, or economic development. Provisions of the TDSIC statute require that, among other things, requests for recovery include a seven-year plan of eligible investments. Once the plan is approved by the IURC, 80 percent of eligible costs can be recovered using a periodic rate adjustment mechanism. The cost recovery mechanism is referred to as a TDSIC mechanism. Recoverable costs include a return on, and of, the investment, including AFUDC, post in service carrying charges, operation and maintenance expenses, depreciation, and property taxes. The remaining 20 percent of recoverable costs are to be deferred for future recovery in the public utility’s next general rate case. The periodic rate adjustment mechanism is capped at an annual increase of no more than two percent of total retail revenues. On October 3, 2013, NIPSCO filed its gas TDSIC seven-year plan of eligible investments for a total of approximately $710 million with the IURC. On April 30, 2014, the IURC issued an order approving NIPSCO's gas TDSIC seven-year plan. On May 29, 2014, the NIPSCO Industrial Group filed a Notice of Appeal with the Indiana Court of Appeals in response to the IURC's April 30, 2014 ruling. Subsequently, the NIPSCO Industrial Group filed a Voluntary Notice of Dismissal, which was granted with prejudice.

	On September 12, 2014, Columbia of Ohio filed an application that seeks authority to establish a regulatory asset and defer, for accounting and financial reporting purposes, the expenditures to be incurred in implementing Columbia of Ohio’s Pipeline Safety Program. Columbia of Ohio is requesting authority to defer Pipeline Safety Program costs of up to $15 million annually. Comments are due November 17, 2014, and Reply Comments are due December 2, 2014.

	On November 25, 2013, Columbia of Ohio filed a Notice of Intent to file an application to adjust rates associated with its IRP and DSM Riders. Columbia of Ohio filed its Application on February 28, 2014, requesting authority to increase revenues by approximately $25.5 million. The parties have settled all issues, and on April 7, 2014 filed a stipulation providing for a revenue increase of approximately $25.5 million. On April 23, 2014, Columbia of Ohio received approval of its annual infrastructure replacement and demand-side management rider request from the PUCO. New rates became effective April 30, 2014.

	On September 16, 2013, Columbia of Massachusetts filed its Peak Period GAF for the period November 1, 2013 through April 30, 2014, and its Peak Period 2012-2013 GAF Reconciliation. On January 17, 2014, Columbia of Massachusetts filed a revision to the GAF effective February 1, 2014, and on February 18, 2014, Columbia of Massachusetts filed its second revision to the GAF effective March 1, 2014, to eliminate Columbia of Massachusetts’s projected Peak Period under-collection of $50.0 million. On February 28, 2014, the Massachusetts DPU approved a revised GAF subject to further review and reconciliation to recover approximately $25 million of the anticipated under-collection and defer recovery of the remaining $25 million to November 2014 through April 2015, and thus, this deferred amount has been incorporated into the proposed GAF as filed on September 16, 2014, in Columbia of Massachusetts’s 2014-2015 Peak Period GAF filing.

	On August 4, 2014, Columbia of Massachusetts filed its 2014-2015 Peak Period LDAF and on September 16, 2014, Columbia of Massachusetts filed its 2014 PEF and its 2014 RAAF, each with a proposed effective date of November 1, 2014. Columbia of Massachusetts expects approval of the 2014-2015 LDAF by October 31, 2014. Columbia of Massachusetts also expects approval of the 2014 PEF and 2014 RAAF by October 31, 2014, subject to further investigation and reconciliation.

	On April 16, 2013, Columbia of Massachusetts submitted a filing with the Massachusetts DPU requesting an annual revenue requirement increase of $30.1 million. Pursuant to the procedural schedule for this case, on September 3, 2013, Columbia of Massachusetts filed its updated revenue requirement of $29.5 million and on October 16, 2013, filed an updated cost of service for $30 million. A final revenue requirement update of $29.9 million was filed on December 16, 2013. On February 28, 2014, the Massachusetts DPU issued an order granting an annual revenue requirement increase of $19.3 million effective March 1, 2014, and the compliance filing associated with the order has been approved.

	On March 21, 2014, Columbia of Pennsylvania filed a base rate case with the Pennsylvania PUC, seeking a revenue increase of approximately $54.1 million annually. The case is driven by Columbia of Pennsylvania’s capital investment program which exceeds $180 million in both 2014 and 2015 as well as new pipeline safety-related operation and maintenance expenditures. Columbia of Pennsylvania seeks Pennsylvania PUC approval to implement additional rates to recover costs that are projected to be incurred after the implementation of those new rates, as authorized by the Pennsylvania General Assembly with the passage of Act 11 of 2012. Columbia of Pennsylvania's filing seeks to implement rates in December 2014 under which Columbia of Pennsylvania would immediately begin to recover costs that are projected for the twelve-month period ending December 31, 2015. On September 5, 2014, the parties to the rate case filed a joint petition which seeks approval of a full settlement. If the settlement is approved, Columbia of Pennsylvania will be authorized to increase its annual base revenues by $32.5 million. The administrative law judge assigned to the case issued a Recommended Decision on October 17, 2014, in which he recommended that the settlement be approved, without modification. A final order from the Pennsylvania PUC is expected in the fourth quarter of 2014.

	On April 30, 2014, Columbia of Virginia filed a base rate case with the VSCC seeking an annual revenue increase of $31.8 million, which includes $6.9 million in annual revenues currently collected as a separate infrastructure replacement rider on customers’ bills under the Virginia SAVE Plan Act. The SAVE rider will be reset to zero and these revenues will be moved into non-gas base rates, resulting in a proposed net revenue increase of $24.9 million per year. Columbia of Virginia also seeks to recover costs related to its implementation of pipeline safety programs and forward looking adjustments to its capital investments and changes in operating costs projected to occur during the rate year ending September 30, 2015. In addition, Columbia of Virginia is proposing a change from volumetric based (Mcf) billing to thermal based (Btu) billing. The VSCC issued a procedural order in the case on May 28, 2014 which scheduled the case for hearing on December 9, 2014. New rates are subject to refund and became effective October 1, 2014.

	Cost Recovery and Trackers. A significant portion of the distribution companies' revenue is related to the recovery of gas costs, the review and recovery of which occurs via standard regulatory proceedings. All states require periodic review of actual gas procurement activity to determine prudence and to permit the recovery of prudently incurred costs related to the supply of gas for customers. NiSource distribution companies have historically been found prudent in the procurement of gas supplies to serve customers.

	Certain operating costs of the NiSource distribution companies are significant, recurring in nature, and generally outside the control of the distribution companies. Some states allow the recovery of such costs via cost tracking mechanisms. Such tracking mechanisms allow for abbreviated regulatory proceedings in order for the distribution companies to implement charges and recover appropriate costs. Tracking mechanisms allow for more timely recovery of such costs as compared with more traditional cost recovery mechanisms. Examples of such mechanisms include GCR adjustment mechanisms, tax riders, gas energy efficiency programs, and bad debt recovery mechanisms.

	Comparability of Gas Distribution Operations line item operating results is impacted by regulatory trackers that allow for the recovery in rates of certain costs such as bad debt expenses. Increases in the expenses that are subject to trackers result in a corresponding increase in net revenues and therefore have essentially no impact on total operating income results.

	Certain NiSource distribution companies have completed rate proceedings involving infrastructure replacement or are embarking upon regulatory initiatives to replace significant portions of their operating systems that are nearing the end of their useful lives. Each LDC's approach to cost recovery may be unique, given the different laws, regulations and precedent that exist in each jurisdiction.

	As further discussed above, NIPSCO has approval from the IURC to recover certain costs for transmission, distribution and storage system improvements. On August 28, 2014, NIPSCO filed its gas TDSIC-1 with the IURC for ratemaking and accounting relief associated with the eligible investments, which included $4.4 million of net capital expenditures for the period ended June 30, 2014. This filing includes changes to the revenue requirement mechanism to be consistent with the IURC order in the electric TDSIC case and revised seven-year plan eligible investment projections. An order is expected in the first quarter of 2015.

	Columbia Pipeline Group Operations Regulatory Matters

	Significant Rate Developments. On January 30, 2014, Columbia Transmission received FERC approval of its December 2013 filing to recover costs associated with the first year of its comprehensive system modernization program. During 2013, Columbia Transmission completed more than 30 individual projects representing a total investment of about $300 million. The program includes replacement of aging pipeline and compressor facilities, enhancements to system inspection capabilities, and improvements in real-time analytics and control systems. Recovery of the 2013 investments began on February 1, 2014.
	The second year of the program includes planned modernization investments of approximately $330 million. Columbia Transmission and its customers have agreed to the initial five years of the comprehensive modernization program, with an opportunity to mutually extend the agreement.

	Cost Recovery Trackers. A significant portion of the regulated transmission and storage companies' revenue is related to the recovery of their operating costs, the review and recovery of which occurs via standard regulatory proceedings with the FERC under section 4 of the Natural Gas Act. However, certain operating costs of the NiSource regulated transmission and storage companies are significant and recurring in nature, such as fuel for compression and lost and unaccounted for gas, which is settled in-kind and reflected net of recoveries in operating expenses. The FERC allows for the recovery of such costs via cost tracking mechanisms. These tracking mechanisms allow the transmission and storage companies' rates to fluctuate in response to changes in certain operating costs or conditions as they occur to facilitate the timely recovery of its costs incurred. The tracking mechanisms involve a rate adjustment that is filed at a predetermined frequency, typically annually, with the FERC and is subject to regulatory review before new rates go into effect. Other such costs under regulatory tracking mechanisms include third-party pipeline transportation, electric compression, certain environmental related expenses, and certain operational purchases and sales of natural gas.

	Electric Operations Regulatory Matters

	Significant Rate Developments. On July 19, 2013, NIPSCO filed its electric TDSIC, further discussed above, with the IURC. The filing included the seven-year plan of eligible investments for a total of approximately $1.1 billion with the majority of the spend occurring in years 2016 through 2020. On February 17, 2014, the IURC issued an order approving NIPSCO’s seven-year plan of eligible investments. The Order also granted NIPSCO ratemaking relief associated with the eligible investments through a rate adjustment mechanism. On March 10, 2014, the OUCC filed a Petition for Reconsideration with the IURC, and the IURC denied that Petition for Reconsideration on May 7, 2014. In addition, the NIPSCO Industrial Group and the OUCC have filed Notices of Appeal with the Indiana Court of Appeals in response to the IURC's ruling, which are still pending.

	On November 12, 2013, several industrial customers, including INDIEC, filed a complaint at the FERC regarding the 12.38% base ROE used to set the MISO Transmission Owners' transmission rates and requested a reduction in the base ROE to 9.15%. The complaint requested that FERC limit the capital structure of MISO Transmission Owners to no more than 50% common equity for ratemaking purposes and that FERC eliminate incentive adders for membership in a RTO. On October 16, 2014, FERC issued an Order that dismissed the portions of the complaint that challenged Transmission Owner capital structures and incentive adders; set the base ROE for hearing and suspended to allow for settlement; set a refund effective date of November 12, 2013; and directed the parties to the new two-step discounted cash flow methodology established by FERC in Opinion No. 531 in Docket No. EL11-77-001. NIPSCO is unable to estimate the impact of this complaint or the timing of any potential impact at this time.

	Cost Recovery and Trackers. A significant portion of NIPSCO's revenue is related to the recovery of fuel costs to generate power and purchased power. These costs are recovered through a FAC, a standard, quarterly, “summary” regulatory proceeding in Indiana.

	Certain operating costs of the Electric Operations are significant, recurring in nature, and generally outside the control of NIPSCO. The IURC allows for recovery of such costs via cost tracking mechanisms. Such tracking mechanisms allow for abbreviated regulatory proceedings in order for NIPSCO to implement charges and recover appropriate costs. Tracking mechanisms allow for more timely recovery of such costs as compared with more traditional cost recovery mechanisms. Examples of such mechanisms include electric energy efficiency programs, MISO non-fuel costs and revenues, federally mandated costs, resource capacity charges, and environmental related costs.

	NIPSCO has approval from the IURC to recover certain environmental related costs through an ECT. Under the ECT, NIPSCO is permitted to recover (1) AFUDC and a return on the capital investment expended by NIPSCO to implement environmental compliance plan projects through an ECRM and (2) related operation and maintenance and depreciation expenses once the environmental facilities become operational through an EERM. On August 1, 2014, NIPSCO filed ECR-24 which included $658.4 million of net capital expenditures for the period ended June 30, 2014. An order is expected in the fourth quarter of 2014.

	As further discussed above, NIPSCO has approval from the IURC to recover certain costs for transmission and distribution system improvements. On August 28, 2014, NIPSCO filed its electric TDSIC-1 with the IURC for ratemaking and accounting relief associated with the eligible investments, which included $19.4 million of net capital expenditures for the period ended June 30, 2014. An order is expected in the fourth quarter of 2014.

Fair_Value

Fair Value	9 Months Ended
	Sep. 30, 2014
Fair Value Disclosures [Abstract]	'
Fair Value	'
	Fair Value

	A. Fair Value Measurements
	Recurring Fair Value Measurements. The following tables present financial assets and liabilities measured and recorded at fair value on NiSource’s Condensed Consolidated Balance Sheets (unaudited) on a recurring basis and their level within the fair value hierarchy as of September 30, 2014 and December 31, 2013:



	Recurring Fair Value Measurements	Quoted Prices in			Significant			Significant				Balance as of September 30, 2014
	September 30, 2014 (in millions)	Active Markets			Other			Unobservable
		for Identical			Observable			Inputs
		Assets			Inputs			(Level 3)
		(Level 1)			(Level 2)
	Assets
	Price risk management assets:
	Commodity financial price risk programs	$	0.7		$	—		$	—			$	0.7

	Available-for-sale securities	31.6			103.6			—				135.2

	Total	$	32.3		$	103.6		$	—			$	135.9

	Liabilities
	Price risk management liabilities:
	Commodity financial price risk programs	$	3.5		$	—		$	0.9			$	4.4

	Total	$	3.5		$	—		$	0.9			$	4.4




	Recurring Fair Value Measurements	Quoted Prices in			Significant			Significant				Balance as of
	December 31, 2013 (in millions)	Active Markets			Other			Unobservable				December 31, 2013
		for Identical			Observable			Inputs
		Assets			Inputs			(Level 3)
		(Level 1)			(Level 2)
	Assets
	Price risk management assets:
	Commodity financial price risk programs	$	2.1		$	—		$	—			$	2.1

	Interest rate risk activities	—			21.1			—				21.1

	Available-for-sale securities	25.3			96.1			—				121.4

	Total	$	27.4		$	117.2		$	—			$	144.6

	Liabilities
	Price risk management liabilities:
	Commodity Financial price risk programs	$	1.6		$	—		$	0.1			$	1.7

	Total	$	1.6		$	—		$	0.1			$	1.7

	Price risk management assets and liabilities include commodity exchange-traded and non-exchange-based derivative contracts. Exchange-traded derivative contracts are based on unadjusted quoted prices in active markets and are classified within Level 1. These financial assets and liabilities are secured with cash on deposit with the exchange; therefore nonperformance risk has not been incorporated into these valuations. Certain non-exchange-traded derivatives are valued using broker or over-the-counter, on-line exchanges. In such cases, these non-exchange-traded derivatives are classified within Level 2. Non-exchange-based derivative instruments include swaps, forwards, and options. In certain instances, these instruments may utilize models to measure fair value. NiSource uses a similar model to value similar instruments. Valuation models utilize various inputs that include quoted prices for similar assets or liabilities in active markets, quoted prices for identical or similar assets or liabilities in markets that are not active, other observable inputs for the asset or liability, and market-corroborated inputs, i.e., inputs derived principally from or corroborated by observable market data by correlation or other means. Where observable inputs are available for substantially the full term of the asset or liability, the instrument is categorized in Level 2. Certain derivatives trade in less active markets with a lower availability of pricing information and models may be utilized in the valuation. When such inputs have a significant impact on the measurement of fair value, the instrument is categorized in Level 3. Credit risk is considered in the fair value calculation of derivative instruments that are not exchange-traded. Credit exposures are adjusted to reflect collateral agreements which reduce exposures. As of September 30, 2014 and December 31, 2013, there were no material transfers between fair value hierarchies. Additionally, there were no changes in the method or significant assumptions used to estimate the fair value of NiSource’s financial instruments.
	At December 31, 2013, price risk management assets also include fixed-to-floating interest rate swaps, which are designated as fair value hedges, as a means to achieve NiSource’s targeted level of variable-rate debt as a percent of total debt. NiSource used a calculation of future cash inflows and estimated future outflows related to the swap agreements, which we discounted and netted to determine the current fair value. Additional inputs to the present value calculation include the contract terms, as well as market parameters such as current and projected interest rates and volatility. As they are based on observable data and valuations of similar instruments, the interest rate swaps are categorized in Level 2 in the fair value hierarchy. Credit risk is considered in the fair value calculation of the interest rate swap. On July 15, 2014, $500.0 million of fixed-to-variable interest rate swaps expired, whereby NiSource Finance received payments based upon a fixed 5.40% interest rate and paid a floating interest rate amount based on U.S. 6-month BBA LIBOR plus an average of 0.78% per annum.
	Available-for-sale securities are investments pledged as collateral for trust accounts related to NiSource’s wholly-owned insurance company. Available-for-sale securities are included within “Other investments” in the Condensed Consolidated Balance Sheets (unaudited). Securities classified within Level 1 include U.S. Treasury debt securities which are highly liquid and are actively traded in over-the-counter markets. NiSource values corporate and mortgage-backed debt securities using a matrix pricing model that incorporates market-based information. These securities trade less frequently and are classified within Level 2. Total gains and losses from available-for-sale securities are included in other comprehensive income (loss). The amortized cost, gross unrealized gains and losses, and fair value of available-for-sale debt securities at September 30, 2014 and December 31, 2013 were:



	September 30, 2014 (in millions)	Amortized			Gross Unrealized Gains			Gross Unrealized Losses				Fair
		Cost										Value
	Available-for-sale debt securities
	U.S. Treasury	$	34.3		$	0.2		$	(0.3	)		$	34.2

	Corporate/Other	101			0.9			(0.9		)		101

Total Available-for-sale debt securities	$	135.3		$	1.1		$	(1.2	)		$	135.2

December 31, 2013 (in millions)	Amortized			Gross Unrealized Gains			Gross Unrealized Losses				Fair
	Cost										Value
Available-for-sale debt securities
U.S. Treasury	$	30.3		$	0.3		$	(0.5	)		$	30.1

Corporate/Other	91.5			1.1			(1.3		)		91.3

Total Available-for-sale debt securities	$	121.8		$	1.4		$	(1.8	)		$	121.4

For the three months ended September 30, 2014 and 2013, the net realized gain on the sale of available-for-sale U.S. Treasury debt securities was zero and $0.1 million, respectively. For the three months ended September 30, 2014 and 2013, the net realized gain on the sale of available-for-sale Corporate/Other bond debt securities was $0.1 million and zero, respectively.
For the nine months ended September 30, 2014 and 2013, the net realized gain on the sale of available-for-sale U.S. Treasury debt securities was $0.1 million and $0.5 million, respectively. For the nine months ended September 30, 2014 and 2013, the net realized gain on the sale of available-for-sale Corporate/Other bond debt securities was $0.3 million.
The cost of maturities sold is based upon specific identification. At September 30, 2014, approximately $4.9 million of U.S. Treasury debt securities have maturities of less than a year while the remaining securities have maturities of greater than one year. At September 30, 2014, approximately $6.2 million of Corporate/Other bonds have maturities of less than a year while the remaining securities have maturities of greater than one year.
There are no material items in the fair value reconciliation of Level 3 assets and liabilities measured at fair value on a recurring basis for the three and nine months ended September 30, 2014 and 2013.



Non-recurring Fair Value Measurements. There were no significant non-recurring fair value measurements recorded during the nine months ended September 30, 2014.

B. Other Fair Value Disclosures for Financial Instruments. The carrying amount of cash and cash equivalents, restricted cash, notes receivable, customer deposits and short-term borrowings is a reasonable estimate of fair value due to their liquid or short-term nature. NiSource’s long-term borrowings 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. The fair values of these securities are estimated based on the quoted market prices for the same or similar issues or on the rates offered for securities of the same remaining maturities. Certain premium costs associated with the early settlement of long-term debt are not taken into consideration in determining fair value. These fair value measurements are classified as Level 2 within the fair value hierarchy. For the nine months ended September 30, 2014 and 2013, there were no changes in the method or significant assumptions used to estimate the fair value of the financial instruments.

The carrying amount and estimated fair values of financial instruments were as follows:



(in millions)	Carrying			Estimated Fair			Carrying				Estimated Fair
	Amount as of			Value as of			Amount as of				Value as of
	30-Sep-14			30-Sep-14			Dec. 31, 2013				Dec. 31, 2013
Long-term debt (including current portion)	$	8,416.10		$	9,338.20		$	8,135.30			$	8,697.30

Transfers_Of_Financial_Assets

Transfers Of Financial Assets	9 Months Ended
	Sep. 30, 2014
Transfers and Servicing [Abstract]	'
Transfers Of Financial Assets	'
	Transfers of Financial Assets
	Transfers of accounts receivable are accounted for as secured borrowings resulting in the recognition of short-term borrowings on the Condensed Consolidated Balance Sheets (unaudited). The maximum amount of debt that can be recognized related to NiSource’s accounts receivable programs is $515 million.
	All accounts receivables sold to the commercial paper conduits are valued at face value, which approximates fair value due to their short-term nature. The amount of the undivided percentage ownership interest in the accounts receivables sold is determined in part by required loss reserves under the agreements. Below is information about the accounts receivable securitization agreements entered into by NiSource’s subsidiaries.
	Columbia of Ohio is under an agreement to sell, without recourse, substantially all of its trade receivables, as they originate, to CGORC, a wholly-owned subsidiary of Columbia of Ohio. CGORC, in turn, is party to an agreement with BTMU and BNS under the terms of which it sells an undivided percentage ownership interest in its accounts receivable to commercial paper conduits sponsored by BTMU and BNS. This agreement was last renewed on October 17, 2014. The maximum seasonal program limit under the terms of the current agreement is $240 million. The current agreement expires on October 16, 2015, and can be further renewed if mutually agreed to by all parties. As of September 30, 2014, $70.8 million of accounts receivable had been transferred by CGORC. CGORC is a separate corporate entity from NiSource and Columbia of Ohio, with its own separate obligations, and upon a liquidation of CGORC, CGORC’s obligations must be satisfied out of CGORC’s assets prior to any value becoming available to CGORC’s stockholder.
	NIPSCO is under an agreement to sell, without recourse, substantially all of its trade receivables, as they originate, to NARC, a wholly-owned subsidiary of NIPSCO. NARC, in turn, is party to an agreement with PNC and Mizuho under the terms of which it sells an undivided percentage ownership interest in its accounts receivable to commercial paper conduits sponsored by PNC and Mizuho. This agreement was last renewed on August 27, 2014. The maximum seasonal program limit under the terms of the current agreement is $200 million. The current agreement expires on August 26, 2015, and can be further renewed if mutually agreed to by all parties. As of September 30, 2014, $125.0 million of accounts receivable had been transferred by NARC. NARC is a separate corporate entity from NiSource and NIPSCO, with its own separate obligations, and upon a liquidation of NARC, NARC’s obligations must be satisfied out of NARC’s assets prior to any value becoming available to NARC’s stockholder.
	Columbia of Pennsylvania is under an agreement to sell, without recourse, substantially all of its trade receivables, as they originate, to CPRC, a wholly-owned subsidiary of Columbia of Pennsylvania. CPRC, in turn, is party to an agreement with BTMU under the terms of which it sells an undivided percentage ownership interest in its accounts receivable to a commercial paper conduit sponsored by BTMU. The maximum seasonal program limit under the terms of the agreement is $75 million. The agreement with BTMU was renewed on March 11, 2014, having a current scheduled termination date of March 10, 2015, and can be further renewed if mutually agreed to by both parties. As of September 30, 2014, $10.0 million of accounts receivable had been transferred by CPRC. CPRC is a separate corporate entity from NiSource and Columbia of Pennsylvania, with its own separate obligations, and upon a liquidation of CPRC, CPRC’s obligations must be satisfied out of CPRC’s assets prior to any value becoming available to CPRC’s stockholder.
	The following table reflects the gross and net receivables transferred as well as short-term borrowings related to the securitization transactions as of September 30, 2014 and December 31, 2013 for Columbia of Ohio, NIPSCO and Columbia of Pennsylvania:



	(in millions)	September 30, 2014		31-Dec-13
	Gross Receivables	$	374	$	610.9

	Less: Receivables not transferred	168.2		345.8

	Net receivables transferred	$	205.8	$	265.1

	Short-term debt due to asset securitization	$	205.8	$	265.1

	Columbia of Ohio, NIPSCO and Columbia of Pennsylvania remain responsible for collecting on the receivables securitized and the receivables cannot be sold to another party.

Goodwill

Goodwill	9 Months Ended
Goodwill	Sep. 30, 2014
Goodwill and Intangible Assets Disclosure [Abstract]	'
Goodwill	'
	Goodwill

	NiSource 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, which is consistent with the level of discrete financial information reviewed by operating segment management. NiSource's three reporting units are Columbia Distribution Operations, Columbia Transmission Operations and NIPSCO Gas Distribution Operations.

	NiSource's goodwill assets as of September 30, 2014 were $3.7 billion pertaining primarily to the acquisition of Columbia on November 1, 2000. Of this amount, approximately $2.0 billion is allocated to Columbia Transmission Operations and $1.7 billion is allocated to Columbia Distribution Operations. In addition, NIPSCO Gas Distribution Operations' goodwill assets of $17.8 million at September 30, 2014 relate to the purchase of Northern Indiana Fuel and Light in March 1993 and Kokomo Gas in February 1992.

	NiSource completed a quantitative ("step 1") fair value measurement of its reporting units during the May 1, 2012 goodwill test. The test indicated that the fair value of each of the reporting units that carry or are allocated goodwill substantially exceeded their carrying values, indicating that no impairment existed.

	ASU 2011-08 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.

	NiSource applied the qualitative step 0 analysis to its reporting units for the annual impairment test performed as of May 1, 2014. For the current year test, NiSource assessed various assumptions, events and circumstances that would have affected the estimated fair value of the reporting units as compared to its base line May 1, 2012 step 1 fair value measurement. The results of this assessment indicated that it is not more likely than not that its reporting unit fair values are less than the reporting unit carrying values.

	NiSource considered whether there were any events or changes in circumstances subsequent to the annual test that would reduce the fair value of any of the reporting units below their carrying amounts and necessitate another goodwill impairment test. No such indicators were noted that would require a subsequent goodwill impairment testing during the third quarter.

Income_Taxes

Income Taxes	9 Months Ended
Income Taxes	Sep. 30, 2014
Income Tax Disclosure [Abstract]	'
Income Taxes	'
	Income Taxes
	NiSource’s interim effective tax rates reflect the estimated annual effective tax rates for 2014 and 2013, adjusted for tax expense associated with certain discrete items. The effective tax rates for the three months ended September 30, 2014 and 2013 were 45.1% and 36.0%, respectively. The effective tax rate for the nine months ended September 30, 2014 and 2013 were 37.7% and 34.7%, respectively. These effective tax rates differ from the Federal tax rate of 35% primarily due to the effects of tax credits, state income taxes, utility ratemaking, and other permanent book-to-tax differences.
	The increase in the three month effective tax rate of 9.1% in 2014 versus 2013 is primarily due to a change in the estimated annual effective tax rate due to a revision in estimated nontaxable income during the third quarter of 2014. The increase in the year-to-date effective tax rate of 3.0% is primarily due to the impact of the Indiana tax rate change, see below for further information, and deferred tax adjustments recorded in 2013 related to state apportionment changes.

	On March 25, 2014, the governor of Indiana signed into law Senate Bill 1, which among other things, lowers the corporate income tax rate from 6.5% to 4.9% over six years beginning on July 1, 2015. The reduction in the tax rate will impact deferred income taxes and tax related regulatory assets and liabilities recoverable in the ratemaking process. In addition, other deferred tax assets and liabilities, primarily deferred tax assets related to the Indiana net operating loss carry forward, will be reduced to reflect the lower rate at which these temporary differences and tax benefits will be realized. In the first quarter of 2014, NiSource recorded tax expense of $7.1 million to reflect the effect of this rate change. This expense is largely attributable to the remeasurement of the Indiana net operating loss at the 4.9% rate. The majority of NiSource's tax temporary differences are related to NIPSCO's utility plant. The remeasurement of these temporary differences at 4.9% was recorded as a reduction of a regulatory asset.

	There were no material changes recorded in 2014 to NiSource's uncertain tax positions as of December 31, 2013.

Pension_And_Other_Postretireme

Pension And Other Postretirement Benefits	9 Months Ended
	Sep. 30, 2014
Pension and Other Postretirement Benefit Expense [Abstract]	'
Pension And Other Postretirement Benefits	'
	Pension and Other Postretirement Benefits

	NiSource provides defined contribution plans and noncontributory defined benefit retirement plans that cover its employees. Benefits under the defined benefit retirement plans reflect the employees’ compensation, years of service and age at retirement. Additionally, NiSource provides health care and life insurance benefits for certain retired employees. The majority of employees may become eligible for these benefits if they reach retirement age while working for NiSource. The expected cost of such benefits is accrued during the employees’ years of service. Current rates of rate-regulated companies include postretirement benefit costs, including amortization of the regulatory assets that arose prior to inclusion of these costs in rates. For most plans, cash contributions are remitted to grantor trusts.

	For the nine months ended September 30, 2014, NiSource has contributed $35.3 million to its pension plans and $29.3 million to its other postretirement benefit plans.

	The following tables provide the components of the plans’ net periodic benefits cost for the three and nine months ended September 30, 2014 and 2013:



		Pension Benefits						Other Postretirement
								Benefits
	Three Months Ended September 30, (in millions)	2014			2013			2014			2013
	Components of Net Periodic Benefit Cost
	Service cost	$	8.7		$	9		$	2		$	3

	Interest cost	27.2			24.9			7			8

	Expected return on assets	(45.3		)	(42.0		)	(9.3		)	(7.6		)
	Amortization of transition obligation	—			—			—			0.2

	Amortization of prior service cost (credit)	0.1			—			(1.4		)	(0.2		)

	Recognized actuarial loss	11.9			18.9			0.2			2.8

	Settlement loss	—			4			—			—

	Total Net Periodic Benefit Cost (Credit)	$	2.6		$	14.8		$	(1.5	)	$	6.2



		Pension Benefits						Other Postretirement
								Benefits
	Nine Months Ended September 30, (in millions)	2014			2013			2014			2013
	Components of Net Periodic Benefit Cost
	Service cost	$	26.1		$	27.7		$	6.5		$	9

	Interest cost	81.8			73.5			23			24.2

	Expected return on assets	(135.9		)	(126.5		)	(27.5		)	(22.8		)
	Amortization of transition obligation	—			—			—			0.4

	Amortization of prior service cost (credit)	0.1			0.2			(2.9		)	(0.6		)

	Recognized actuarial loss	35.7			59.3			0.3			8.4

	Settlement loss	—			28.3			—			—

	Total Net Periodic Benefit Cost (Credit)	$	7.8		$	62.5		$	(0.6	)	$	18.6


	In 2013, NiSource pension plans had lump sum payouts exceeding the plans' 2013 service cost plus interest cost and, therefore, settlement accounting was required.

Variable_Interests_and_Variabl

Variable Interests and Variable Interest Entities	9 Months Ended
Variable Interests and Variable Interest Entities	Sep. 30, 2014
Variable Interest Entities And Equity Investments [Abstract]	'
Variable Interests and Variable Interest Entities	'
	Variable Interests and Variable Interest Entities
	In general, a VIE is an entity that (1) has an insufficient amount of at-risk equity to permit the entity to finance its activities without additional financial subordinated support provided by any parties, (2) whose at-risk equity owners, as a group, do not have power, through voting rights or similar rights, to direct activities of the entity that most significantly impact the entity’s economic performance or (3) whose at-risk owners do not absorb the entity’s losses or receive the entity’s residual return. A VIE is required to be consolidated by a company if that company is determined to be the primary beneficiary of the VIE.
	NiSource consolidates those VIEs for which it is the primary beneficiary. NiSource considers quantitative and qualitative elements in determining the primary beneficiary. Qualitative measures include the ability to control an entity and the obligation to absorb losses or the right to receive benefits.
	NiSource’s analysis includes an assessment of guarantees, operating leases, purchase agreements, and other contracts, as well as its investments and joint ventures. For items that have been identified as variable interests, or where there is involvement with an identified VIE, an in-depth review of the relationship between the relevant entities and NiSource is made to evaluate qualitative and quantitative factors to determine the primary beneficiary, if any, and whether additional disclosures would be required under the current standard.

	NIPSCO has a service agreement with Pure Air, a general partnership between Air Products and Chemicals, Inc. and First Air Partners LP, under which Pure Air provides scrubber services to reduce sulfur dioxide emissions for Units 7 and 8 at the Bailly Generating Station. NiSource has made an exhaustive effort to obtain information needed from Pure Air to determine the status of Pure Air as a VIE. However, NIPSCO has not been able to obtain this information and, as a result, it is unclear whether Pure Air is a VIE and if NIPSCO is the primary beneficiary. NIPSCO will continue to request the information required to determine whether Pure Air is a VIE. NIPSCO has no exposure to loss related to the service agreement with Pure Air and payments under this agreement were $17.0 million and $17.1 million for the nine months ended September 30, 2014 and 2013, respectively.

LongTerm_Debt_LongTerm_Debt

Long-Term Debt Long-Term Debt	9 Months Ended
Long-Term Debt Long-Term Debt	Sep. 30, 2014
Long-term Debt, Unclassified [Abstract]	'
Debt Disclosure [Text Block]	'
	Long-Term Debt

	On August 20, 2014, NiSource Finance negotiated a $750.0 million three-year bank term loan with a syndicate of banks which carries a floating interest rate of BBA LIBOR plus 100 basis points.

	On July 15, 2014, NiSource Finance redeemed $500.0 million of 5.40% senior unsecured notes at maturity.

ShortTerm_Borrowings

Short-Term Borrowings	9 Months Ended
	Sep. 30, 2014
Short-term Debt [Abstract]	'
Short-Term Borrowings	'
	Short-Term Borrowings
	NiSource Finance maintains a $2.0 billion revolving credit facility with a syndicate of banks led by Barclays Capital with a termination date of September 28, 2018. The purpose of the facility is to fund ongoing working capital requirements including the provision of liquidity support for NiSource’s $1.5 billion commercial paper program, provide for issuance of letters of credit, and also for general corporate purposes. At September 30, 2014, NiSource had no outstanding borrowings under this facility.
	NiSource Finance's commercial paper program has a program limit of up to $1.5 billion with a dealer group comprised of Barclays, Citigroup, Credit Suisse, RBS and Wells Fargo. Commercial paper issuances are supported by available capacity under NiSource’s $2.0 billion unsecured revolving credit facility. At September 30, 2014, NiSource had $1,105.3 million of commercial paper outstanding.
	As of September 30, 2014, NiSource had $31.2 million of stand-by letters of credit outstanding of which $15.0 million were under the revolving credit facility. At December 31, 2013, NiSource had $31.6 million of stand-by letters of credit outstanding of which $14.3 million were under the revolving credit facility.
	Transfers of accounts receivable are accounted for as secured borrowings resulting in the recognition of short-term debt on the Condensed Consolidated Balance Sheets (unaudited) in the amount of $205.8 million and $265.1 million as of September 30, 2014 and December 31, 2013, respectively. Refer to Note 8, “Transfers of Financial Assets,” for additional information.



	(in millions)	September 30,		December 31,
		2014		2013
	Commercial Paper weighted average interest rate of 0.67% and 0.70% at September 30, 2014 and December 31, 2013, respectively.	$	1,105.30	$	433.6

	Accounts receivable securitization facility borrowings	205.8		265.1

	Total Short-Term Borrowings	$	1,311.10	$	698.7


	Given their turnover is less than 90 days, cash flows related to the borrowings and repayments of the items listed above are presented net in the Condensed Statements of Consolidated Cash Flows (unaudited).

ShareBased_Compensation

Share-Based Compensation	9 Months Ended
Share-Based Compensation	Sep. 30, 2014
Share-based Compensation [Abstract]	'
Share-Based Compensation	'
	Share-Based Compensation
	The stockholders approved and adopted the NiSource Inc. 2010 Omnibus Incentive Plan (the “Omnibus Plan”), at the Annual Meeting of Stockholders held on May 11, 2010. 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 NiSource available for awards is 8,000,000 plus the number of shares subject to outstanding awards granted under either the 1994 Plan (defined below) or the Director Stock Incentive Plan ("Director Plan") that expire or terminate for any reason. No further awards are permitted to be granted under the 1994 Plan or the Director Plan. At September 30, 2014, there were 6,260,962 shares reserved for future awards under the Omnibus Plan.
	Prior to May 11, 2010, NiSource issued long-term equity incentive grants to key management employees under a long-term incentive plan approved by stockholders on April 13, 1994 (“1994 Plan”). The types of equity awards previously authorized under the 1994 Plan did not significantly differ from those permitted under the Omnibus Plan.
	NiSource recognized stock-based employee compensation expense of $16.3 million and $8.8 million for the three months ended September 30, 2014 and 2013, respectively, as well as related tax benefits of $5.4 million and $3.2 million, respectively. For the nine months ended September 30, 2014 and 2013, stock-based employee compensation expense of $27.3 million and $17.5 million was recognized, respectively, as well as related tax benefit of $10.1 million and $6.1 million, respectively.
	As of September 30, 2014, the total remaining unrecognized compensation cost related to nonvested awards amounted to $26.8 million, which will be amortized over the weighted-average remaining requisite service period of 2.2 years.
	Stock Options. As of September 30, 2014, approximately 0.1 million options were outstanding and exercisable with a weighted average strike price of $22.62. No options were granted during the nine months ended September 30, 2014 and 2013. As of September 30, 2014, the aggregate intrinsic value for the options outstanding and exercisable was $2.0 million. During the nine months ended September 30, 2014 and 2013, cash received from the exercise of options was $6.8 million and $22.6 million, respectively.
	Restricted Stock Units and Restricted Stock. During the nine months ended September 30, 2014, NiSource granted 148,133 restricted stock units and shares of restricted stock, subject to service conditions. The total grant date fair value of restricted stock units and shares of restricted stock was $4.8 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, which will be expensed, net of forfeitures, over the vesting period which is generally three years. As of September 30, 2014, 309,829 nonvested (all of which are expected to vest) restricted stock units and shares of restricted stock were granted and outstanding.
	Performance Shares. During the nine months ended September 30, 2014, NiSource granted 535,037 performance shares subject to service and performance conditions. The grant date fair value of the awards was $16.6 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 and performance period. As of September 30, 2014, 1,735,551 nonvested performance shares were granted and outstanding.
	401(k) Match, Profit Sharing and Company Contribution. NiSource has a voluntary 401(k) savings plan covering eligible employees that allows for periodic discretionary matches as a percentage of each participant’s contributions payable in shares of common stock. NiSource 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 exempt employees hired after January 1, 2010, receive a non-elective company contribution of three percent of eligible pay payable in shares of common stock. For the quarters ended September 30, 2014 and 2013, NiSource recognized 401(k) match, profit sharing and non-elective contribution expense of $10.5 million and $7.9 million, respectively. For the nine months ended September 30, 2014 and 2013, NiSource recognized 401(k) match, profit sharing and non-elective contribution expenses of $27.4 million and $22.2 million, respectively.

Other_Commitments_And_Continge

Other Commitments And Contingencies	9 Months Ended
	Sep. 30, 2014
Other Commitments and Contingencies [Abstract]	'
Commitments and Contingencies	'
	Other Commitments and Contingencies
	A. Guarantees and Indemnities. As a part of normal business, NiSource 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 subsidiary on a stand-alone basis, thereby facilitating the extension of sufficient credit to accomplish the subsidiaries’ intended commercial purposes. The total guarantees and indemnities in existence at September 30, 2014 and the years in which they expire were:



	(in millions)	Total		2014		2015		2016		2017		2018		After
	Guarantees of subsidiaries debt	$	7,960.50	$	—	$	230	$	616.5	$	1,257.00	$	800	$	5,057.00

	Accounts receivable securitization	205.8		205.8		—		—		—		—		—

	Lines of credit	1,105.30		1,105.30		—		—		—		—		—

	Letters of credit	31.2		—		31.2		—		—		—		—

	Other guarantees	142.4		7.4		29.5		—		—		—		105.5

	Total commercial commitments	$	9,445.20	$	1,318.50	$	290.7	$	616.5	$	1,257.00	$	800	$	5,162.50


	Guarantees of Subsidiaries Debt. NiSource has guaranteed the payment of $8.0 billion of debt for various wholly-owned subsidiaries including NiSource Finance and Columbia of Massachusetts, and through a support agreement, Capital Markets, which is reflected on NiSource’s Condensed Consolidated Balance Sheets (unaudited). The subsidiaries are required to comply with certain covenants under the debt indenture and in the event of default, NiSource would be obligated to pay the debt’s principal and related interest. NiSource does not anticipate its subsidiaries will have any difficulty maintaining compliance. On October 3, 2011, NiSource executed a Second Supplemental Indenture to the original Columbia of Massachusetts Indenture dated April 1, 1991, for the specific purpose of guaranteeing Columbia of Massachusetts’ outstanding medium-term notes.
	Lines and Letters of Credit and Accounts Receivable Advances. NiSource Finance maintains a $2.0 billion revolving credit facility with a syndicate of banks led by Barclays Capital with a termination date of September 28, 2018. The purpose of the facility is to fund ongoing working capital requirements including the provision of liquidity support for NiSource’s $1.5 billion commercial paper program, provide for the issuance of letters of credit, and also for general corporate purposes. At September 30, 2014, NiSource had no borrowings under its five-year revolving credit facility, $1,105.3 million in commercial paper outstanding and $205.8 million outstanding under its accounts receivable securitization agreements. At September 30, 2014, NiSource issued stand-by letters of credit of approximately $31.2 million for the benefit of third parties. See Note 14, “Short-Term Borrowings,” for additional information.
	Other Guarantees or Obligations. NiSource has additional purchase and sales agreement guarantees totaling $25.6 million, which guarantee performance of the seller’s covenants, agreements, obligations, liabilities, representations and warranties under the agreements. No amounts related to the purchase and sales agreement guarantees are reflected in the Condensed Consolidated Balance Sheets (unaudited). Management believes that the likelihood NiSource would be required to perform or otherwise incur any significant losses associated with any of the aforementioned guarantees is remote.
	NiSource has on deposit a letter of credit with Union Bank, N.A., Collateral Agent, in a debt service reserve account in association with Millennium's notes as required under the Deposit and Disbursement Agreement that governs the Millennium notes. This account is to be drawn upon by the note holders in the event that Millennium is delinquent on its principal and interest payments. The value of NiSource’s letter of credit represents 47.5% (NiSource’s ownership percentage in Millennium) of the debt service reserve account requirement, or $16.2 million. The total exposure for NiSource is $16.2 million. NiSource has an accrued liability of $1.5 million related to the inception date fair value of this guarantee as of September 30, 2014.
	NiSource has issued other guarantees supporting derivative related payments associated with operating leases for many of its subsidiaries and for other agreements entered into by its current and former subsidiaries.
	B. Other Legal Proceedings. In the normal course of its business, NiSource and its subsidiaries have been named as defendants in various legal proceedings. In the opinion of management, the ultimate disposition of these currently asserted claims will not have a material impact on NiSource’s consolidated financial statements.
	C. Environmental Matters. NiSource operations are subject to environmental statutes and regulations related to air quality, water quality, hazardous waste and solid waste. NiSource believes that it is in substantial compliance with those environmental regulations currently applicable to its operations and believes that it has all necessary permits to conduct its operations.
	It is management’s continued intent to address environmental issues in cooperation with regulatory authorities in such a manner as to achieve mutually acceptable compliance plans. However, there can be no assurance that fines and penalties will not be incurred. Management expects a significant portion of environmental assessment and remediation costs to be recoverable through rates for certain NiSource companies.
	As of September 30, 2014 and December 31, 2013, NiSource had recorded an accrual of approximately $130.9 million and $143.9 million, respectively, to cover environmental remediation at various sites. The current portion of this accrual is included in "Legal and environmental" in the Condensed Consolidated Balance Sheets (unaudited). The noncurrent portion is included in "Other noncurrent liabilities" in the Condensed Consolidated Balance Sheets (unaudited). NiSource 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. These expenditures are not currently estimable at some sites. NiSource periodically adjusts its accrual as information is collected and estimates become more refined.
	Air
	The actions listed below could require further reductions in emissions from various emission sources. NiSource will continue to closely monitor developments in these matters.

	Climate Change. On June 2, 2014, the EPA proposed a GHG performance standard for existing fossil-fuel fired electric generating units under section 111(d) of the Clean Air Act. The proposed rule establishes state-specific CO2 emission rate goals and requires each state to submit a plan indicating how the generating units within the state will meet the EPA's emission rate goal. Final CO2 emission rate standards are expected to be set by the EPA in June 2015, and state plans are required to be submitted to the EPA as early as June 2016. The cost to comply with this rule will depend on a number of factors, including the requirements of the final federal regulation and the level of NIPSCO's required GHG reductions. It is possible that this new rule, comprehensive federal or state GHG legislation, or other GHG regulation could result in additional expense or compliance costs that could materially impact NiSource's financial results.

	National Ambient Air Quality Standards. The CAA requires the EPA to set NAAQS for particulate matter and five other pollutants considered harmful to public health and the environment. Periodically the EPA imposes new or modifies existing NAAQS. States that contain areas that do not meet the new or revised standards must take steps to maintain or achieve compliance with the standards. These steps could include additional pollution controls on boilers, engines, turbines, and other facilities owned by electric generation, gas distribution, and gas transmission operations.

	The following NAAQS were recently added or modified:

	Particulate Matter: In December 2009, the EPA issued area designations for the 2006 24-hour PM2.5 standard, and several counties in which NiSource operates were designated as non-attainment. In addition, a final rule was promulgated in December 2012 that lowered the annual PM2.5 standard from 15 to 12 µg/m3. NiSource will continue to monitor these matters and cannot estimate their impact at this time.

	Ozone (eight hour): On September 2, 2011, the EPA announced it would implement its 2008 eight-hour ozone NAAQS rather than tightening the standard in 2012. The EPA will review, and possibly propose a new standard in 2014. In addition, the EPA has designated the Chicago metropolitan area, including the area in which NIPSCO operates one of its electric generation facilities, as non-attainment for ozone. NiSource will continue to monitor this matter and cannot estimate the impact of any new rules at this time.

	Nitrogen Dioxide (NO2): The EPA revised the NO2 NAAQS by adding a one-hour standard while retaining the annual standard. The new standard could impact some NiSource 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 NiSource combustion sources may need to be assessed and mitigated. NiSource will continue to monitor this matter and cannot estimate the impact of these rules at this time.

	Waste
	NiSource subsidiaries are potentially responsible parties at waste disposal sites under the CERCLA (commonly known as Superfund) and similar state laws. Additionally, a program has been instituted to identify and investigate former MGP sites where Gas Distribution Operations subsidiaries or predecessors may have liability. The program has identified 66 such sites where liability is probable. Remedial actions at many of these sites are being overseen by state or federal environmental agencies through consent agreements or voluntary remediation agreements.
	NiSource utilizes a probabilistic model to estimate its future remediation costs related to its MGP sites. The model was prepared with the assistance of a third party and incorporates NiSource and general industry experience with remediating MGP sites. NiSource completes an annual refresh of the model in the second quarter of each fiscal year. No material changes to the estimated liability were noted as a result of the refresh completed as of June 30, 2014. The total estimated liability at NiSource related to the facilities subject to remediation was $122.8 million and $129.5 million at September 30, 2014 and December 31, 2013, respectively. The liability represents NiSource’s best estimate of the probable cost to remediate the facilities. NiSource believes that it is reasonably possible that remediation costs could vary by as much as $25 million in addition to the costs noted above. Remediation costs are estimated based on the best available information, applicable remediation standards at the balance sheet date, and experience with similar facilities.
	Additional Issues Related to Individual Business Segments
	The sections below describe various regulatory actions that affect Columbia Pipeline Group Operations and Electric Operations.
	Columbia Pipeline Group Operations.

	Air
	In April 2014, the Pennsylvania DEP proposed a rule, Additional RACT Requirements for Major Sources of NOx and VOCs, which may require emissions reductions from several Columbia Transmission turbines and reciprocating engines. The rule is expected to be finalized by the end of 2014 and would give facilities three years to bring emissions sources into compliance with the reductions required by this rule. Columbia Transmission will continue to monitor developments in this matter and cannot estimate costs at this time.
	Waste
	Columbia Transmission continues to conduct characterization and remediation activities at specific sites under a 1995 AOC (subsequently modified in 1996 and 2007). NiSource utilizes a probabilistic model to estimate its future remediation costs related to the 1995 AOC. The model was prepared with the assistance of a third party and incorporates NiSource and general industry experience with remediating sites. NiSource completes an annual refresh of the model in the second quarter of each fiscal year. No material changes to the liability were noted as a result of the refresh completed as of June 30, 2014. The total remaining liability at Columbia Transmission related to the facilities subject to remediation was $2.8 million and $8.7 million at September 30, 2014 and December 31, 2013, respectively. The liability represents Columbia Transmission’s best estimate of the cost to remediate the facilities or manage the sites. Remediation costs are estimated based on the information available, applicable remediation standards, and experience with similar facilities. Columbia Transmission expects that the remediation for these facilities will be substantially completed in 2015.
	Electric Operations.
	Air
	NIPSCO is subject to a number of new air-quality mandates in the next several years. These mandates require NIPSCO to make capital improvements to its electric generating stations. The cost of capital improvements is estimated to be $860 million, of which approximately $155.8 million remains to be spent. This figure includes additional capital improvements associated with the New Source Review Consent Decree and the Utility Mercury and Air Toxics Standards Rule. NIPSCO believes that the capital costs will likely be recoverable from customers.

	EPA Cross-State Air Pollution Rule / Clean Air Interstate Rule (CAIR) / Transport Rule: On July 6, 2011, the EPA announced its replacement for the 2005 CAIR to reduce the interstate transport of fine particulate matter and ozone. The CSAPR reduces overall emissions of SO2 and NOx by setting state-wide caps on power plant emissions. Implementation of the CSAPR was delayed for several years by litigation, but the EPA recently received permission from a court to begin enforcing CSAPR on January 1, 2015. The EPA’s implementation of CSAPR will not significantly impact NIPSCO's current emissions control plans. NIPSCO utilizes the inventory model in accounting for emission allowances issued under the CAIR program whereby these allowances were recognized at zero cost upon receipt from the EPA. NIPSCO believes its current multi-pollutant compliance plan and New Source Review Consent Decree capital investments will allow NIPSCO to meet the emission requirements of CSAPR.

	Utility Mercury and Air Toxics Standards Rule: On December 16, 2011, the EPA finalized the MATS rule establishing new emissions limits for mercury and other air toxics. Compliance for NIPSCO’s affected units is required by April 2015, or by April 2016 for those affected units that have been approved for a one year compliance extension by IDEM. NIPSCO is implementing an IURC-approved plan for environmental controls to comply with MATS.
	New Source Review: On September 29, 2004, the EPA issued an NOV to NIPSCO for alleged violations of the CAA and the Indiana SIP. The NOV alleged that modifications were made to certain boiler units at three of NIPSCO's generating stations between the years 1985 and 1995 without obtaining appropriate air permits for the modifications. NIPSCO, the EPA, the Department of Justice, and IDEM have settled the matter through a consent decree, entered on July 22, 2011.

Water
On August 15, 2014, the EPA published the final Phase II Rule of the Clean Water Act Section 316(b), which requires all large existing steam electric generating stations to meet certain performance standards to reduce the effects on aquatic organisms at their cooling water intake structures. Under this rule, stations will have to either demonstrate that the performance of their existing fish protection systems meet the new standards or develop new systems, such as a closed-cycle cooling tower. The cost to comply will depend on a number of factors, including evaluation of the various compliance options available under the regulation and permitting-related discussions with IDEM. NIPSCO is currently evaluating these options and cannot estimate the cost of compliance at this time.
On June 7, 2013, the EPA published a proposed rule to amend the effluent limitations guidelines and standards for the Steam Electric Power Generating category. These proposed regulations could impose new water treatment requirements on NIPSCO’s electric generating facilities. NIPSCO will continue to monitor developments in this matter and cannot estimate the cost of compliance at this time.
Waste
On June 21, 2010, the EPA published a proposed rule for regulation of CCRs. The proposal outlines multiple regulatory approaches that the EPA is considering. These proposed regulations could negatively affect NIPSCO’s ongoing byproduct reuse programs and would impose additional requirements on its management of coal combustion residuals. NIPSCO will continue to monitor developments in this matter and cannot estimate the cost of compliance at this time.

D. Other Matters.

Transmission Upgrade Agreements. On February 11, 2014, NIPSCO entered into TUAs with upgrade sponsors to complete upgrades on NIPSCO’s transmission system on behalf of those sponsors. The upgrade sponsors have agreed to reimburse NIPSCO for the total cost to construct transmission upgrades and place them into service, which is estimated at $50.3 million, multiplied by a rate of 1.71 ("the multiplier").

On June 10, 2014, certain upgrade sponsors for both TUAs, filed a complaint at FERC against NIPSCO regarding the multiplier stated in the TUAs. On June 30, 2014, NIPSCO filed an answer defending the terms of the TUAs and the just and reasonable nature of the multiplier charged therein and moved for dismissal of the complaint. NIPSCO will continue to monitor developments in this matter but cannot estimate the impact (if any) on the Condensed Consolidated Financial Statements (unaudited) the complaint will have at this time.

Springfield, Massachusetts. On November 23, 2012, while Columbia of Massachusetts was investigating the source of an odor of gas at a service location in Springfield, Massachusetts, a gas service line was pierced and an explosion occurred. While this explosion impacted multiple buildings and resulted in several injuries, no life threatening injuries or fatalities have been reported. Columbia of Massachusetts is fully cooperating with both the Massachusetts DPU and the Occupational Safety & Health Administration in their investigations of this incident. Columbia of Massachusetts believes any costs associated with damages, injuries, and other losses related to this incident are substantially covered by insurance. Any amounts not covered by insurance are not expected to have a material impact on NiSource's consolidated financial statements. In accordance with GAAP, NiSource recorded any accruals and the related insurance recoveries resulting from this incident on a gross basis within the Condensed Consolidated Balance Sheets (unaudited).

Accumulated_Other_Comprehensiv

Accumulated Other Comprehensive Loss	9 Months Ended
	Sep. 30, 2014
Other Comprehensive Income (Loss), Tax [Abstract]	'
Accumulated Other Comprehensive Loss	'
	Accumulated Other Comprehensive Loss
	The following tables display the components of Accumulated Other Comprehensive Loss for the three and nine months ended September 30, 2014 and 2013:


	Three Months Ended September 30, 2014 (in millions)	Gains and Losses on Securities(1)			Gains and Losses on Cash Flow Hedges(1)			Pension and OPEB Items(1)			Accumulated
											Other
											Comprehensive
											Loss(1)
	Balance as of July 1, 2014	$	0.5		$	(24.5	)	$	(17.4	)	$	(41.4	)

	Other comprehensive income before reclassifications	(0.5		)	—			(0.1		)	(0.6		)

	Amounts reclassified from accumulated other comprehensive income	(0.1		)	0.6			(0.1		)	0.4

	Net current-period other comprehensive (loss) income	(0.6		)	0.6			(0.2		)	(0.2		)

	Balance as of September 30, 2014	$	(0.1	)	$	(23.9	)	$	(17.6	)	$	(41.6	)

	Nine Months Ended September 30, 2014 (in millions)	Gains and Losses on Securities(1)			Gains and Losses on Cash Flow Hedges(1)			Pension and OPEB Items(1)			Accumulated
											Other
											Comprehensive
											Loss(1)
	Balance as of January 1, 2014	$	(0.3	)	$	(25.8	)	$	(17.5	)	$	(43.6	)
	Other comprehensive income before reclassifications	0.5			0.1			(0.4		)	0.2

	Amounts reclassified from accumulated other comprehensive income	(0.3		)	1.8			0.3			1.8

	Net current-period other comprehensive income (loss)	0.2			1.9			(0.1		)	2

	Balance as of September 30, 2014	$	(0.1	)	$	(23.9	)	$	(17.6	)	$	(41.6	)


	Three Months Ended September 30, 2013 (in millions)	Gains and Losses on Securities(1)			Gains and Losses on Cash Flow Hedges(1)			Pension and OPEB Items(1)			Accumulated
											Other
											Comprehensive
											Loss(1)
	Balance as of July 1, 2013	$	(0.7	)	$	(27.2	)	$	(34.1	)	$	(62.0	)
	Other comprehensive income before reclassifications	1			(0.1		)	(0.6		)	0.3

	Amounts reclassified from accumulated other comprehensive income	(0.1		)	0.7			0.7			1.3

	Net current-period other comprehensive income	0.9			0.6			0.1			1.6

	Balance as of September 30, 2013	$	0.2		$	(26.6	)	$	(34.0	)	$	(60.4	)


	Nine Months Ended September 30, 2013 (in millions)	Gains and Losses on Securities(1)			Gains and Losses on Cash Flow Hedges(1)			Pension and OPEB Items(1)			Accumulated
											Other
											Comprehensive
											Loss(1)
	Balance as of January 1, 2013	$	2.6		$	(28.6	)	$	(39.5	)	$	(65.5	)

	Other comprehensive income before reclassifications	(1.9		)	(0.1		)	2.6			0.6

	Amounts reclassified from accumulated other comprehensive income	(0.5		)	2.1			2.9			4.5

	Net current-period other comprehensive (loss) income	(2.4		)	2			5.5			5.1

	Balance as of September 30, 2013	$	0.2		$	(26.6	)	$	(34.0	)	$	(60.4	)

	(1)All amounts are net of tax. Amounts in parentheses indicate debits.

	Equity Investment
As Millennium is an equity method investment, NiSource is required to recognize a proportional share of Millennium’s OCI. The remaining unrecognized loss at September 30, 2014 of $16.9 million, net of tax, related to terminated interest rate swaps is being amortized over the period ending June 2025 into earnings using the effective interest method through interest expense as interest payments are made by Millennium. The unrecognized loss of $16.9 million and $17.7 million at September 30, 2014 and December 31, 2013, respectively, is included in gains and losses on cash flow hedges above.

Business_Segment_Information

Business Segment Information	9 Months Ended
	Sep. 30, 2014
Segment Reporting [Abstract]	'
Business Segment Information	'
	Business Segment Information
	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. NiSource's Chief Executive Officer is the chief operating decision maker.
	At September 30, 2014, NiSource’s operations are divided into three primary business segments. The Gas Distribution Operations segment provides natural gas service and transportation for residential, commercial and industrial customers in Ohio, Pennsylvania, Virginia, Kentucky, Maryland, Indiana and Massachusetts. The Columbia Pipeline Group Operations segment offers gas transportation and storage services for LDCs, marketers and industrial and commercial customers located in northeastern, mid-Atlantic, midwestern and southern states along with unregulated businesses that include midstream services and development of mineral rights positions. The Electric Operations segment provides electric service in 20 counties in the northern part of Indiana.
	The following table provides information about business segments. NiSource uses operating income as its primary measurement for each of the reported segments and makes decisions on finance, dividends and taxes at the corporate level on a consolidated basis. Segment revenues include intersegment sales to affiliated subsidiaries, which are eliminated in consolidation. Affiliated sales are recognized on the basis of prevailing market, regulated prices or at levels provided for under contractual agreements. Operating income is derived from revenues and expenses directly associated with each segment.



		Three Months Ended						Nine Months Ended September 30,
		September 30,
	(in millions)	2014			2013			2014			2013
	Revenues
	Gas Distribution Operations
	Unaffiliated	$	411.9		$	409.5		$	2,593.80		$	2,126.80

	Intersegment	—			—			0.3			0.2

	Total	411.9			409.5			2,594.10			2,127.00

	Columbia Pipeline Group Operations
	Unaffiliated	285.7			251.3			900.2			752

	Intersegment	31.9			31.4			106.5			105.9

	Total	317.6			282.7			1,006.70			857.9

	Electric Operations
	Unaffiliated	424.4			413.6			1,279.90			1,175.90

	Intersegment	0.3			0.1			0.6			0.5

	Total	424.7			413.7			1,280.50			1,176.40

	Corporate and Other
	Unaffiliated	1.9			2.4			5.6			5.8

	Intersegment	138.1			119.6			393.8			351.3

	Total	140			122			399.4			357.1

	Eliminations	(170.3		)	(151.1		)	(501.2		)	(457.9		)
	Consolidated Gross Revenues	$	1,123.90		$	1,076.80		$	4,779.50		$	4,060.50

	Operating Income (Loss)
	Gas Distribution Operations	$	0.8		$	(5.0	)	$	362.4		$	279.1

	Columbia Pipeline Group Operations	94.4			98.7			357			321

	Electric Operations	76.9			87.5			218.7			212.2

	Corporate and Other	(14.3		)	(4.8		)	(27.0		)	(13.0		)
	Consolidated Operating Income	$	157.8		$	176.4		$	911.1		$	799.3

Supplemental_Cash_Flow_Informa

Supplemental Cash Flow Information	9 Months Ended
	Sep. 30, 2014
Supplemental Cash Flow Information [Abstract]	'
Supplemental Cash Flow Information	'
	Supplemental Cash Flow Information
	The following table provides additional information regarding NiSource’s Condensed Statements of Consolidated Cash Flows (unaudited) for the nine months ended September 30, 2014 and 2013:


		Nine Months Ended September 30,
	(in millions)	2014		2013
	Supplemental Disclosures of Cash Flow Information
	Non-cash transactions:
	Capital expenditures included in current liabilities	$	213.9	$	202.7

	Assets acquired under a capital lease	69.9		5.7

	Schedule of interest and income taxes paid:
	Cash paid for interest, net of interest capitalized amounts	$	375	$	359.4

	Cash paid for income taxes	12.2		8.5

Earnings_Per_Share_Tables

Earnings Per Share (Tables)	9 Months Ended
	Sep. 30, 2014
Earnings Per Share [Abstract]	'
Computation Of Diluted Average Common Shares	'


		Three Months Ended		Nine Months Ended September 30,
		September 30,
	(in thousands)	2014	2013	2014	2013
	Denominator
	Basic average common shares outstanding	315,418	312,842	314,889	312,053

	Dilutive potential common shares:
	Stock options	32	112	30	102

	Shares contingently issuable under employee stock plans	725	369	649	327

	Shares restricted under stock plans	451	490	438	477

	Diluted Average Common Shares	316,626	313,813	316,006	312,959

Discontinued_Operations_And_As1

Discontinued Operations And Assets And Liabilities Held For Sale (Tables)	9 Months Ended
	Sep. 30, 2014
Discontinued Operations And Assets And Liabilities Held For Sale [Abstract]	'
Assets And Liabilities Of Discontinued Operations And Held For Sale	'


		Three Months Ended						Nine Months Ended September 30,
		September 30,
	(in millions)	2014			2013			2014			2013
	Net Revenues from Discontinued Operations	$	—		$	0.4		$	—		$	1.3

	(Loss) Income from discontinued operations	(0.2		)	0.1			(1.0		)	12.2

	Income tax (benefit) expense	(0.1		)	—			(0.4		)	4.7

	(Loss) Income from Discontinued Operations - net of taxes	$	(0.1	)	$	0.1		$	(0.6	)	$	7.5

	(Loss) Gain on Disposition of Discontinued Operations - net of taxes	$	—		$	(1.5	)	$	—		$	34.9

Asset_Retirement_Obligations_T

Asset Retirement Obligations (Tables)	9 Months Ended
	Sep. 30, 2014
Asset Retirement Obligation [Abstract]	'
Changes In Company's Liability For Asset Retirement Obligations	'


	(in millions)	2014			2013
	Balance as of January 1,	$	174.4		$	160.4

	Accretion expense	1.2			0.9

	Accretion recorded as a regulatory asset/liability	6.3			6.5

	Additions	2.3			9.7

	Settlements	(1.4		)	(1.3		)
	Change in estimated cash flows(1)	(7.6		)	(0.7		)
	Balance as of September 30,	$	175.2		$	175.5

	(1)The change in estimated cash flows for 2014 is primarily attributed to changes in estimated costs to retire pipeline.

Fair_Value_Tables

Fair Value (Tables)	9 Months Ended
	Sep. 30, 2014
Fair Value Disclosures [Abstract]	'
Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis	'


	Recurring Fair Value Measurements	Quoted Prices in		Significant		Significant			Balance as of September 30, 2014
	September 30, 2014 (in millions)	Active Markets		Other		Unobservable
		for Identical		Observable		Inputs
		Assets		Inputs		(Level 3)
		(Level 1)		(Level 2)
	Assets
	Price risk management assets:
	Commodity financial price risk programs	$	0.7	$	—	$	—		$	0.7

	Available-for-sale securities	31.6		103.6		—			135.2

	Total	$	32.3	$	103.6	$	—		$	135.9

	Liabilities
	Price risk management liabilities:
	Commodity financial price risk programs	$	3.5	$	—	$	0.9		$	4.4

	Total	$	3.5	$	—	$	0.9		$	4.4




	Recurring Fair Value Measurements	Quoted Prices in		Significant		Significant			Balance as of
	December 31, 2013 (in millions)	Active Markets		Other		Unobservable			December 31, 2013
		for Identical		Observable		Inputs
		Assets		Inputs		(Level 3)
		(Level 1)		(Level 2)
	Assets
	Price risk management assets:
	Commodity financial price risk programs	$	2.1	$	—	$	—		$	2.1

	Interest rate risk activities	—		21.1		—			21.1

	Available-for-sale securities	25.3		96.1		—			121.4

	Total	$	27.4	$	117.2	$	—		$	144.6

	Liabilities
	Price risk management liabilities:
	Commodity Financial price risk programs	$	1.6	$	—	$	0.1		$	1.7

	Total	$	1.6	$	—	$	0.1		$	1.7

Available-For-Sale Debt Securities	'


	September 30, 2014 (in millions)	Amortized		Gross Unrealized Gains		Gross Unrealized Losses			Fair
		Cost							Value
	Available-for-sale debt securities
	U.S. Treasury	$	34.3	$	0.2	$	(0.3	)	$	34.2

	Corporate/Other	101		0.9		(0.9		)	101

	Total Available-for-sale debt securities	$	135.3	$	1.1	$	(1.2	)	$	135.2

	December 31, 2013 (in millions)	Amortized		Gross Unrealized Gains		Gross Unrealized Losses			Fair
		Cost							Value
	Available-for-sale debt securities
	U.S. Treasury	$	30.3	$	0.3	$	(0.5	)	$	30.1

	Corporate/Other	91.5		1.1		(1.3		)	91.3

	Total Available-for-sale debt securities	$	121.8	$	1.4	$	(1.8	)	$	121.4

Carrying Amount And Estimated Fair Values Of Financial Instruments	'



	(in millions)	Carrying		Estimated Fair		Carrying			Estimated Fair
		Amount as of		Value as of		Amount as of			Value as of
		30-Sep-14		30-Sep-14		Dec. 31, 2013			Dec. 31, 2013
	Long-term debt (including current portion)	$	8,416.10	$	9,338.20	$	8,135.30		$	8,697.30

Transfers_Of_Financial_Assets_

Transfers Of Financial Assets (Tables)	9 Months Ended
	Sep. 30, 2014
Transfers and Servicing [Abstract]	'
Schedule Of Gross And Net Receivables Transferred As Well As Short-Term Borrowings Related To The Securitization Transactions	'



	(in millions)	September 30, 2014		31-Dec-13
	Gross Receivables	$	374	$	610.9

	Less: Receivables not transferred	168.2		345.8

	Net receivables transferred	$	205.8	$	265.1

	Short-term debt due to asset securitization	$	205.8	$	265.1

Pension_And_Other_Postretireme1

Pension And Other Postretirement Benefits (Tables)	9 Months Ended
	Sep. 30, 2014
Pension and Other Postretirement Benefit Expense [Abstract]	'
Components Of The Plans' Net Periodic Benefits Cost	'



		Pension Benefits						Other Postretirement
								Benefits
	Three Months Ended September 30, (in millions)	2014			2013			2014			2013
	Components of Net Periodic Benefit Cost
	Service cost	$	8.7		$	9		$	2		$	3

	Interest cost	27.2			24.9			7			8

	Expected return on assets	(45.3		)	(42.0		)	(9.3		)	(7.6		)
	Amortization of transition obligation	—			—			—			0.2

	Amortization of prior service cost (credit)	0.1			—			(1.4		)	(0.2		)

	Recognized actuarial loss	11.9			18.9			0.2			2.8

	Settlement loss	—			4			—			—

	Total Net Periodic Benefit Cost (Credit)	$	2.6		$	14.8		$	(1.5	)	$	6.2



		Pension Benefits						Other Postretirement
								Benefits
	Nine Months Ended September 30, (in millions)	2014			2013			2014			2013
	Components of Net Periodic Benefit Cost
	Service cost	$	26.1		$	27.7		$	6.5		$	9

	Interest cost	81.8			73.5			23			24.2

	Expected return on assets	(135.9		)	(126.5		)	(27.5		)	(22.8		)
	Amortization of transition obligation	—			—			—			0.4

	Amortization of prior service cost (credit)	0.1			0.2			(2.9		)	(0.6		)

	Recognized actuarial loss	35.7			59.3			0.3			8.4

	Settlement loss	—			28.3			—			—

	Total Net Periodic Benefit Cost (Credit)	$	7.8		$	62.5		$	(0.6	)	$	18.6

ShortTerm_Borrowings_Tables

Short-Term Borrowings (Tables)	9 Months Ended
	Sep. 30, 2014
Short-term Debt [Abstract]	'
Schedule Of Short-Term Borrowings	'


	(in millions)	September 30,		December 31,
		2014		2013
	Commercial Paper weighted average interest rate of 0.67% and 0.70% at September 30, 2014 and December 31, 2013, respectively.	$	1,105.30	$	433.6

	Accounts receivable securitization facility borrowings	205.8		265.1

	Total Short-Term Borrowings	$	1,311.10	$	698.7

Other_Commitments_And_Continge1

Other Commitments And Contingencies (Tables)	9 Months Ended
	Sep. 30, 2014
Other Commitments and Contingencies [Abstract]	'
Schedule of Guarantor Obligations	'
	The total guarantees and indemnities in existence at September 30, 2014 and the years in which they expire were:



	(in millions)	Total		2014		2015		2016		2017		2018		After
	Guarantees of subsidiaries debt	$	7,960.50	$	—	$	230	$	616.5	$	1,257.00	$	800	$	5,057.00

	Accounts receivable securitization	205.8		205.8		—		—		—		—		—

	Lines of credit	1,105.30		1,105.30		—		—		—		—		—

	Letters of credit	31.2		—		31.2		—		—		—		—

	Other guarantees	142.4		7.4		29.5		—		—		—		105.5

	Total commercial commitments	$	9,445.20	$	1,318.50	$	290.7	$	616.5	$	1,257.00	$	800	$	5,162.50

Accumulated_Other_Comprehensiv1

Accumulated Other Comprehensive Loss (Tables)	9 Months Ended
	Sep. 30, 2014
Other Comprehensive Income (Loss), Tax [Abstract]	'
Components Of Accumulated Other Comprehensive Loss	'


	Three Months Ended September 30, 2014 (in millions)	Gains and Losses on Securities(1)			Gains and Losses on Cash Flow Hedges(1)			Pension and OPEB Items(1)			Accumulated
											Other
											Comprehensive
											Loss(1)
	Balance as of July 1, 2014	$	0.5		$	(24.5	)	$	(17.4	)	$	(41.4	)

	Other comprehensive income before reclassifications	(0.5		)	—			(0.1		)	(0.6		)

	Amounts reclassified from accumulated other comprehensive income	(0.1		)	0.6			(0.1		)	0.4

	Net current-period other comprehensive (loss) income	(0.6		)	0.6			(0.2		)	(0.2		)

	Balance as of September 30, 2014	$	(0.1	)	$	(23.9	)	$	(17.6	)	$	(41.6	)

	Nine Months Ended September 30, 2014 (in millions)	Gains and Losses on Securities(1)			Gains and Losses on Cash Flow Hedges(1)			Pension and OPEB Items(1)			Accumulated
											Other
											Comprehensive
											Loss(1)
	Balance as of January 1, 2014	$	(0.3	)	$	(25.8	)	$	(17.5	)	$	(43.6	)
	Other comprehensive income before reclassifications	0.5			0.1			(0.4		)	0.2

	Amounts reclassified from accumulated other comprehensive income	(0.3		)	1.8			0.3			1.8

	Net current-period other comprehensive income (loss)	0.2			1.9			(0.1		)	2

	Balance as of September 30, 2014	$	(0.1	)	$	(23.9	)	$	(17.6	)	$	(41.6	)


	Three Months Ended September 30, 2013 (in millions)	Gains and Losses on Securities(1)			Gains and Losses on Cash Flow Hedges(1)			Pension and OPEB Items(1)			Accumulated
											Other
											Comprehensive
											Loss(1)
	Balance as of July 1, 2013	$	(0.7	)	$	(27.2	)	$	(34.1	)	$	(62.0	)
	Other comprehensive income before reclassifications	1			(0.1		)	(0.6		)	0.3

	Amounts reclassified from accumulated other comprehensive income	(0.1		)	0.7			0.7			1.3

	Net current-period other comprehensive income	0.9			0.6			0.1			1.6

	Balance as of September 30, 2013	$	0.2		$	(26.6	)	$	(34.0	)	$	(60.4	)


	Nine Months Ended September 30, 2013 (in millions)	Gains and Losses on Securities(1)			Gains and Losses on Cash Flow Hedges(1)			Pension and OPEB Items(1)			Accumulated
											Other
											Comprehensive
											Loss(1)
	Balance as of January 1, 2013	$	2.6		$	(28.6	)	$	(39.5	)	$	(65.5	)

	Other comprehensive income before reclassifications	(1.9		)	(0.1		)	2.6			0.6

	Amounts reclassified from accumulated other comprehensive income	(0.5		)	2.1			2.9			4.5

	Net current-period other comprehensive (loss) income	(2.4		)	2			5.5			5.1

	Balance as of September 30, 2013	$	0.2		$	(26.6	)	$	(34.0	)	$	(60.4	)

	(1)All amounts are net of tax. Amounts in parentheses indicate debits.

Business_Segment_Information_T

Business Segment Information (Tables)	9 Months Ended
	Sep. 30, 2014
Segment Reporting [Abstract]	'
Schedule Of Operating Income Derived From Revenues And Expenses By Segment	'


		Three Months Ended						Nine Months Ended September 30,
		September 30,
	(in millions)	2014			2013			2014			2013
	Revenues
	Gas Distribution Operations
	Unaffiliated	$	411.9		$	409.5		$	2,593.80		$	2,126.80

	Intersegment	—			—			0.3			0.2

	Total	411.9			409.5			2,594.10			2,127.00

	Columbia Pipeline Group Operations
	Unaffiliated	285.7			251.3			900.2			752

	Intersegment	31.9			31.4			106.5			105.9

	Total	317.6			282.7			1,006.70			857.9

	Electric Operations
	Unaffiliated	424.4			413.6			1,279.90			1,175.90

	Intersegment	0.3			0.1			0.6			0.5

	Total	424.7			413.7			1,280.50			1,176.40

	Corporate and Other
	Unaffiliated	1.9			2.4			5.6			5.8

	Intersegment	138.1			119.6			393.8			351.3

	Total	140			122			399.4			357.1

	Eliminations	(170.3		)	(151.1		)	(501.2		)	(457.9		)
	Consolidated Gross Revenues	$	1,123.90		$	1,076.80		$	4,779.50		$	4,060.50

	Operating Income (Loss)
	Gas Distribution Operations	$	0.8		$	(5.0	)	$	362.4		$	279.1

	Columbia Pipeline Group Operations	94.4			98.7			357			321

	Electric Operations	76.9			87.5			218.7			212.2

	Corporate and Other	(14.3		)	(4.8		)	(27.0		)	(13.0		)
	Consolidated Operating Income	$	157.8		$	176.4		$	911.1		$	799.3

Supplemental_Cash_Flow_Informa1

Supplemental Cash Flow Information (Tables)	9 Months Ended
	Sep. 30, 2014
Supplemental Cash Flow Information [Abstract]	'
Additional Information Regarding Condensed Statements Of Consolidated Cash Flows	'


		Nine Months Ended September 30,
	(in millions)	2014		2013
	Supplemental Disclosures of Cash Flow Information
	Non-cash transactions:
	Capital expenditures included in current liabilities	$	213.9	$	202.7

	Assets acquired under a capital lease	69.9		5.7

	Schedule of interest and income taxes paid:
	Cash paid for interest, net of interest capitalized amounts	$	375	$	359.4

	Cash paid for income taxes	12.2		8.5

Earnings_Per_Share_Table_Detai

Earnings Per Share Table (Details)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Earnings Per Share [Abstract]	'	'	'	'
Basic Average Common Shares Outstanding	315,418	312,842	314,889	312,053
Stock options	32	112	30	102
Shares contingently issuable under employee stock plans	725	369	649	327
Shares restricted under stock plans	451	490	438	477
Weighted Average Number of Shares Outstanding, Diluted	316,626	313,813	316,006	312,959

Discontinued_Operations_And_As2

Discontinued Operations And Assets And Liabilities Held For Sale (Summary Of Gain (Loss) On Disposition Of Discontinued Operations Net Of Taxes) (Details) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Discontinued Operations And Assets And Liabilities Held For Sale [Abstract]	'	'	'	'
Net Revenues from Discontinued Operations	$0	$0.40	$0	$1.30
(Loss) Income from discontinued operations	-0.2	0.1	-1	12.2
Income tax (benefit) expense	-0.1	0	-0.4	4.7
(Loss) Income from Discontinued Operations - net of taxes	-0.1	0.1	-0.6	7.5
(Loss) Gain on Disposition of Discontinued Operations - net of taxes	$0	($1.50)	$0	$34.90

Asset_Retirement_Obligations_C

Asset Retirement Obligations (Changes In Company's Liability For Asset Retirement Obligations) (Details) (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014		Sep. 30, 2013
Beginning Balance	$174.40		$160.40
Accretion expense	1.2		0.9
Accretion recorded as a regulatory asset/liability	6.3		6.5
Additions	2.3		9.7
Settlements	-1.4		-1.3
Change in estimated cash flows	-7.6	[1]	-0.7	[1]
Ending Balance	$175.20		$175.50

[1]	The change in estimated cash flows for 2014 is primarily attributed to changes in estimated costs to retire pipeline.

Regulatory_Matters_Narrative_D

Regulatory Matters (Narrative) (Details) (USD $)

0 Months Ended

4 Months Ended

0 Months Ended

9 Months Ended

0 Months Ended

12 Months Ended

0 Months Ended

In Millions, unless otherwise specified

Sep. 12, 2014

Feb. 28, 2014

Apr. 23, 2014

Feb. 28, 2014

Feb. 18, 2014

Dec. 16, 2013

Sep. 03, 2013

Apr. 16, 2013

Oct. 16, 2013

Sep. 05, 2014

Mar. 21, 2014

Sep. 30, 2014

Apr. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Nov. 12, 2013

Feb. 17, 2014

Oct. 03, 2013

Aug. 01, 2014

Aug. 28, 2014

Columbia Of Ohio [Member]

Columbia Of Massachusetts [Member]

Columbia Of Pennsylvania [Member]

Columbia Of Virginia [Member]

Columbia Transmission [Member]

NIPSCO [Member]

Customer Settlement [Member]

ECR 24 [Member]

TDSIC 1 Gas [Member]

TDSIC 1 Electric [Member]

Regulatory Matters [Line Items]

Updated Cost Of Service

$30

Capital Investment Program Amount

180

Annual Revenues Currently Collected As A Separate IRP

6.9

Proposed Net Revenue Increase

24.9

Regulatory Net Capital Expenditures Included In Filing

658.4

4.4

19.4

Modernization Projects Completed

Spend on Eligible Modernization Facilities

300

Projected Peak Undercollection

Deferred Recovery of Projected Peak Undercollection

Annual Capital Cost Recovery Mechanism Limit

330

Seven Year Plan of Eligible Investments Under TDSIC

1,100

710

Requested Regulatory Deferral

Public Utilities, Requested Rate Increase (Decrease), Amount

25.5

29.9

29.5

30.1

32.5

54.1

31.8

Approved Rate Increase (Decrease)

$25.50

$19.30

Public Utilities, Approved Return on Equity, Percentage

12.38%

Public Utilities, Requested Return on Equity, Percentage

9.15%

Fair_Value_Narrative_Details

Fair Value (Narrative) (Details) (USD $)

0 Months Ended

3 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

0 Months Ended

In Millions, unless otherwise specified

Jul. 15, 2014

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Aug. 20, 2014

Jul. 15, 2014

Government [Member]

Corporate/Other Bonds [Member]

London Interbank Offered Rate (LIBOR) [Member]

Fair Value Disclosure [Line Items]

Repayments of Senior Debt

$500

Available-for-sale Securities, Gross Realized Gain (Loss)

0.1

0.5

0.1

0.3

Available-for-sale Securities, Debt Maturities, Next Twelve Months, Fair Value

$4.90

$6.20

Debt Instrument, Interest Rate, Stated Percentage

5.40%

Debt Instrument, Basis Spread on Variable Rate

1.00%

0.78%

Fair_Value_Fair_Value_Of_Finan

Fair Value (Fair Value Of Financial Assets And Liabilities Measured On A Recurring Basis) (Details) (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Millions, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]	'	'
Available-for-sale securities	$135.20	$121.40
Fair value assets measured on recurring basis, total	135.9	144.6
Fair value liabilities measured on recurring basis, total	4.4	1.7
Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]	'	'
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]	'	'
Available-for-sale securities	31.6	25.3
Fair value assets measured on recurring basis, total	32.3	27.4
Fair value liabilities measured on recurring basis, total	3.5	1.6
Significant Other Observable Inputs (Level 2) [Member]	'	'
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]	'	'
Available-for-sale securities	103.6	96.1
Fair value assets measured on recurring basis, total	103.6	117.2
Fair value liabilities measured on recurring basis, total	0	0
Significant Unobservable Inputs (Level 3) [Member]	'	'
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]	'	'
Available-for-sale securities	0	0
Fair value assets measured on recurring basis, total	0	0
Fair value liabilities measured on recurring basis, total	0.9	0.1
Commodity Contract [Member]	'	'
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]	'	'
Fair value assets measured on recurring basis, derivative financial instruments	0.7	2.1
Fair value liabilities measured on recurring basis, derivative financial instruments	4.4	1.7
Commodity Contract [Member] \| Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]	'	'
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]	'	'
Fair value assets measured on recurring basis, derivative financial instruments	0.7	2.1
Fair value liabilities measured on recurring basis, derivative financial instruments	3.5	1.6
Commodity Contract [Member] \| Significant Other Observable Inputs (Level 2) [Member]	'	'
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]	'	'
Fair value assets measured on recurring basis, derivative financial instruments	0	0
Fair value liabilities measured on recurring basis, derivative financial instruments	0	0
Commodity Contract [Member] \| Significant Unobservable Inputs (Level 3) [Member]	'	'
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]	'	'
Fair value assets measured on recurring basis, derivative financial instruments	0	0
Fair value liabilities measured on recurring basis, derivative financial instruments	0.9	0.1
Interest Rate Risk Activities [Member]	'	'
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]	'	'
Fair value assets measured on recurring basis, derivative financial instruments	'	21.1
Interest Rate Risk Activities [Member] \| Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]	'	'
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]	'	'
Fair value assets measured on recurring basis, derivative financial instruments	'	0
Interest Rate Risk Activities [Member] \| Significant Other Observable Inputs (Level 2) [Member]	'	'
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]	'	'
Fair value assets measured on recurring basis, derivative financial instruments	'	21.1
Interest Rate Risk Activities [Member] \| Significant Unobservable Inputs (Level 3) [Member]	'	'
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]	'	'
Fair value assets measured on recurring basis, derivative financial instruments	'	$0

Fair_Value_AvailableForSale_De

Fair Value (Available-For-Sale Debt Securities) (Details) (USD $)	9 Months Ended	12 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Fair Value Disclosure [Line Items]	'	'
Amortized Cost	$135.30	$121.80
Gross Unrealized Gains	1.1	1.4
Gross Unrealized Losses	-1.2	-1.8
Fair Value	135.2	121.4
Government [Member]	'	'
Fair Value Disclosure [Line Items]	'	'
Amortized Cost	34.3	30.3
Gross Unrealized Gains	0.2	0.3
Gross Unrealized Losses	-0.3	-0.5
Fair Value	34.2	30.1
Corporate/Other Bonds [Member]	'	'
Fair Value Disclosure [Line Items]	'	'
Amortized Cost	101	91.5
Gross Unrealized Gains	0.9	1.1
Gross Unrealized Losses	-0.9	-1.3
Fair Value	$101	$91.30

Fair_Value_Carrying_Amount_And

Fair Value (Carrying Amount And Estimated Fair Values Of Financial Instruments) (Details) (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Millions, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Debt Instrument [Line Items]	'	'
Long-term debt (including current portion), Carrying Amount	$8,416.10	$8,135.30
Long-term debt (including current portion), Estimated Fair Value	$9,338.20	$8,697.30

Transfers_Of_Financial_Assets_1

Transfers Of Financial Assets (Narrative) (Details) (USD $)	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2014	Sep. 30, 2014	Sep. 30, 2014	Sep. 30, 2014	Sep. 30, 2014	Sep. 30, 2014	Sep. 30, 2014
In Millions, unless otherwise specified			Columbia Gas Of Ohio Receivables Corporation [Member]	Columbia Gas Of Pennsylvania Receivables Corporation [Member]	NIPSCO Accounts Receivable Corporation [Member]	Maximum [Member]	Maximum [Member]	Maximum [Member]	Maximum [Member]
						Accounts Receivable Program [Member]	Columbia Gas Of Ohio Receivables Corporation [Member]	Columbia Gas Of Pennsylvania Receivables Corporation [Member]	NIPSCO Accounts Receivable Corporation [Member]
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]	'	'	'	'	'	'	'	'	'
Accounts receivable securitization facility borrowings	$205.80	$265.10	'	'	'	$515	'	'	'
Trade receivables, seasonal program maximum	'	'	'	'	'	'	240	75	200
Trade Receivable Agreement Expiration Date	'	'	16-Oct-15	10-Mar-15	26-Aug-15	'	'	'	'
Net receivables transferred	$205.80	$265.10	$70.80	$10	$125	'	'	'	'

Transfers_Of_Financial_Assets_2

Transfers Of Financial Assets (Schedule Of Gross And Net Receivables Transferred As Well As Short-Term Borrowings Related To The Securitization Transactions) (Details) (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Millions, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Gross Receivables	$374	$610.90
Less: Receivables not transferred	168.2	345.8
Net receivables transferred	205.8	265.1
Accounts receivable securitization facility borrowings	$205.80	$265.10

Goodwill_Narrative_Details

Goodwill (Narrative) (Details) (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Goodwill [Line Items]	'	'
Number of reporting units for goodwill	3	'
Goodwill	$3,666.20	$3,666.20
Columbia Transmission [Member]	'	'
Goodwill [Line Items]	'	'
Goodwill	2,000	'
Columbia Distribution [Member]	'	'
Goodwill [Line Items]	'	'
Goodwill	1,700	'
NIPSCO Gas Distribution [Member]	'	'
Goodwill [Line Items]	'	'
Goodwill	$17.80	'

Income_Taxes_Narrative_Details

Income Taxes (Narrative) (Details) (USD $)	3 Months Ended			9 Months Ended		3 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Mar. 31, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Mar. 25, 2014	Mar. 25, 2014
	Sep. 30, 2014	Mar. 31, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Previous [Member]	Current [Member]
Income Taxes [Line Items]	'	'	'	'	'	'	'
Effective income tax rates	45.10%	'	36.00%	37.70%	34.70%	'	'
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate	'	'	'	35.00%	'	'	'
Increase (Decrease) in Effective Tax Rate	9.10%	'	'	3.00%	'	'	'
Corporate Income Tax Rate	'	'	'	'	'	6.50%	4.90%
Tax Expense Recognized Due to Rate Change	'	$7.10	'	'	'	'	'

Pension_And_Other_Postretireme2

Pension And Other Postretirement Benefits (Narrative) (Details) (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014
Pension Plan [Member]	'
Defined Benefit Plan Disclosure [Line Items]	'
Employer contributions	$35.30
Other Postretirement Benefits [Member]	'
Defined Benefit Plan Disclosure [Line Items]	'
Employer contributions	$29.30

Pension_And_Other_Postretireme3

Pension And Other Postretirement Benefits (Components Of The Plans' Net Periodic Benefits Cost) (Details) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Pension Plan [Member]	'	'	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'	'	'
Service Cost	$8.70	$9	$26.10	$27.70
Interest cost	27.2	24.9	81.8	73.5
Expected return on assets	-45.3	-42	-135.9	-126.5
Amortization of transition obligation	0	0	0	0
Amortization of prior service cost (credit)	0.1	0	0.1	0.2
Recognized actuarial loss	11.9	18.9	35.7	59.3
Settlement loss	0	4	0	28.3
Total Net Periodic Benefits Cost	2.6	14.8	7.8	62.5
Other Postretirement Benefits [Member]	'	'	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'	'	'
Service Cost	2	3	6.5	9
Interest cost	7	8	23	24.2
Expected return on assets	-9.3	-7.6	-27.5	-22.8
Amortization of transition obligation	0	0.2	0	0.4
Amortization of prior service cost (credit)	-1.4	-0.2	-2.9	-0.6
Recognized actuarial loss	0.2	2.8	0.3	8.4
Settlement loss	0	0	0	0
Total Net Periodic Benefits Cost	($1.50)	$6.20	($0.60)	$18.60

Variable_Interests_and_Variabl1

Variable Interests and Variable Interest Entities (Narrative) (Details) (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013
Schedule of Equity Method Investments [Line Items]	'	'
Payments made to Pure Air	$17	$17.10

LongTerm_Debt_Long_Term_Debt_N

Long-Term Debt Long Term Debt (Narrative) (Details) (USD $)	0 Months Ended
In Millions, unless otherwise specified	Aug. 20, 2014	Jul. 15, 2014	Aug. 20, 2014	Jul. 15, 2014
Debt Instrument [Line Items]	'	'	'	'
Face amount of notes	'	'	$750	'
Repayments of Senior Debt	'	$500	'	'
Interest rate of long-term debt	'	'	'	5.40%
Debt Instrument, Term	'3 years	'	'	'
London Interbank Offered Rate (LIBOR) [Member]	'	'	'	'
Debt Instrument [Line Items]	'	'	'	'
Debt Instrument, Basis Spread on Variable Rate	1.00%	0.78%	'	'

ShortTerm_Borrowings_Narrative

Short-Term Borrowings (Narrative) (Details) (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Short-term Debt [Line Items]	'	'
Commercial paper outstanding	$1,105.30	$433.60
Revolving credit facility	2,000	'
Revolving Credit Facility, Expiration Date	28-Sep-18	'
Accounts receivable securitization facility borrowings	205.8	265.1
Short-term borrowings	1,311.10	698.7
Letters Of Credit [Member]	'	'
Short-term Debt [Line Items]	'	'
Letters of Credit Outstanding, Amount	31.2	31.6
Revolving Credit Facility [Member]	'	'
Short-term Debt [Line Items]	'	'
Line of Credit Facility, Amount Outstanding	0	'
Commercial Paper [Member]	'	'
Short-term Debt [Line Items]	'	'
Commercial paper outstanding	1,105.30	'
Revolving credit facility	1,500	'
Standby Letters of Credit [Member]	'	'
Short-term Debt [Line Items]	'	'
Line of Credit Facility, Amount Outstanding	$15	$14.30

ShortTerm_Borrowings_Schedule_

Short-Term Borrowings (Schedule Of Short-Term Borrowings) (Details) (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Millions, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Short-term Debt [Line Items]	'	'
Commercial paper	$1,105.30	$433.60
Accounts receivable securitization facility borrowings	205.8	265.1
Total short-term borrowings	1,311.10	698.7
Commercial Paper [Member]	'	'
Short-term Debt [Line Items]	'	'
Commercial paper	$1,105.30	'
Commercial Paper/credit facilities borrowings, weighted average interest rate	0.67%	0.70%

ShareBased_Compensation_Narrat

Share-Based Compensation (Narrative) (Details) (USD $)	3 Months Ended		9 Months Ended
In Millions, except Share data, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	11-May-10
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant	'	'	'	'	8,000,000
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized	6,260,962	'	6,260,962	'	'
Allocated Share-based Compensation Expense	$16.30	$8.80	$27.30	$17.50	'
Employee Service Share-based Compensation, Tax Benefit from Compensation Expense	5.4	3.2	10.1	6.1	'
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized	26.8	'	26.8	'	'
Employee Service Share Based Compensation Nonvested Awards Weighted Average Remaining Requisite Service Period	'	'	'2 years 3 months	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number	100,000	'	100,000	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price	$22.62	'	$22.62	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross	'	'	0	0	'
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value	2	'	2	'	'
Employee Service Share-based Compensation, Cash Received from Exercise of Stock Options	'	'	6.8	22.6	'
Defined Contribution Plan, Cost Recognized	10.5	7.9	27.4	22.2	'
Restricted Awards [Member]	'	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period	'	'	148,133	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Total Fair Value	'	'	4.8	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number	309,829	'	309,829	'	'
Performance Shares [Member]	'	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period	'	'	535,037	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Total Fair Value	'	'	$16.60	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number	1,735,551	'	1,735,551	'	'

Other_Commitments_And_Continge2

Other Commitments And Contingencies (Narrative) (Details) (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Other Commitments And Contingencies [Line Items]	'	'
Revolving credit facility, maximum	$2,000	'
Line of Credit Facility, Expiration Date	28-Sep-18	'
Commercial paper	1,105.30	433.6
Accounts receivable securitization facility borrowings	205.8	265.1
Additional purchase and sales agreement guarantees	25.6	'
Guarantor Obligations, Maximum Exposure, Undiscounted	9,445.20	'
Recorded reserves to cover environmental remediation at various sites	130.9	143.9
Transmission Upgrade Reimbursement	50.3	'
Transmission Upgrade Agreement Multiplier	1.71	'
MGP Sites	'	'
Other Commitments And Contingencies [Line Items]	'	'
Number of waste disposal sites identified by program	66	'
Liability for Estimated Remediation Costs	122.8	129.5
Reasonably possible remediation costs variance from reserve	25	'
Columbia Transmission [Member]	'	'
Other Commitments And Contingencies [Line Items]	'	'
Liability for Estimated Remediation Costs	2.8	8.7
Millennium Pipeline Company, L.L.C [Member]	'	'
Other Commitments And Contingencies [Line Items]	'	'
Percentage of interest in Millennium	47.50%	'
Guarantor Obligations, Maximum Exposure, Undiscounted	16.2	'
Fair value of guarantee obligations	1.5	'
Guarantees Of Subsidiaries Debt [Member]	'	'
Other Commitments And Contingencies [Line Items]	'	'
Guarantor Obligations, Maximum Exposure, Undiscounted	7,960.50	'
Letters Of Credit [Member]	'	'
Other Commitments And Contingencies [Line Items]	'	'
Guarantor Obligations, Maximum Exposure, Undiscounted	31.2	'
Other Guarantees [Member]	'	'
Other Commitments And Contingencies [Line Items]	'	'
Guarantor Obligations, Maximum Exposure, Undiscounted	142.4	'
Maximum [Member] \| NIPSCO [Member]	'	'
Other Commitments And Contingencies [Line Items]	'	'
Remaining Payments for Capital Improvements	155.8	'
Payments for Capital Improvements	860	'
Revolving Credit Facility [Member]	'	'
Other Commitments And Contingencies [Line Items]	'	'
Line of Credit Facility, Amount Outstanding	0	'
Commercial Paper [Member]	'	'
Other Commitments And Contingencies [Line Items]	'	'
Revolving credit facility, maximum	1,500	'
Commercial paper	$1,105.30	'

Other_Commitments_And_Continge3

Other Commitments And Contingencies (Existence And Expiration Of Commercial Commitments) (Details) (USD $)	Sep. 30, 2014
In Millions, unless otherwise specified	Sep. 30, 2014
Other Commitments And Contingencies [Line Items]	'
Guarantee Obligations Maximum Exposure Year One	$1,318.50
Guarantee Obligations Maximum Exposure Year Two	290.7
Guarantee Obligations Maximum Exposure Year Three	616.5
Guarantee Obligations Maximum Exposure Year Four	1,257
Guarantee Obligations Maximum Exposure Year Five	800
Guarantee Obligations Maximum Exposure Thereafter	5,162.50
Guarantor Obligations, Maximum Exposure, Undiscounted	9,445.20
Guarantees of subsidiaries debt	'
Other Commitments And Contingencies [Line Items]	'
Guarantee Obligations Maximum Exposure Year One	0
Guarantee Obligations Maximum Exposure Year Two	230
Guarantee Obligations Maximum Exposure Year Three	616.5
Guarantee Obligations Maximum Exposure Year Four	1,257
Guarantee Obligations Maximum Exposure Year Five	800
Guarantee Obligations Maximum Exposure Thereafter	5,057
Guarantor Obligations, Maximum Exposure, Undiscounted	7,960.50
Accounts Receivable Securitization [Member]	'
Other Commitments And Contingencies [Line Items]	'
Guarantee Obligations Maximum Exposure Year One	205.8
Guarantee Obligations Maximum Exposure Year Two	0
Guarantee Obligations Maximum Exposure Year Three	0
Guarantee Obligations Maximum Exposure Year Four	0
Guarantee Obligations Maximum Exposure Year Five	0
Guarantee Obligations Maximum Exposure Thereafter	0
Guarantor Obligations, Maximum Exposure, Undiscounted	205.8
Lines Of Credit [Member]	'
Other Commitments And Contingencies [Line Items]	'
Guarantee Obligations Maximum Exposure Year One	1,105.30
Guarantee Obligations Maximum Exposure Year Two	0
Guarantee Obligations Maximum Exposure Year Three	0
Guarantee Obligations Maximum Exposure Year Four	0
Guarantee Obligations Maximum Exposure Year Five	0
Guarantee Obligations Maximum Exposure Thereafter	0
Guarantor Obligations, Maximum Exposure, Undiscounted	1,105.30
Letters Of Credit [Member]	'
Other Commitments And Contingencies [Line Items]	'
Guarantee Obligations Maximum Exposure Year One	0
Guarantee Obligations Maximum Exposure Year Two	31.2
Guarantee Obligations Maximum Exposure Year Three	0
Guarantee Obligations Maximum Exposure Year Four	0
Guarantee Obligations Maximum Exposure Year Five	0
Guarantee Obligations Maximum Exposure Thereafter	0
Guarantor Obligations, Maximum Exposure, Undiscounted	31.2
Other Guarantees [Member]	'
Other Commitments And Contingencies [Line Items]	'
Guarantee Obligations Maximum Exposure Year One	7.4
Guarantee Obligations Maximum Exposure Year Two	29.5
Guarantee Obligations Maximum Exposure Year Three	0
Guarantee Obligations Maximum Exposure Year Four	0
Guarantee Obligations Maximum Exposure Year Five	0
Guarantee Obligations Maximum Exposure Thereafter	105.5
Guarantor Obligations, Maximum Exposure, Undiscounted	$142.40

Accumulated_Other_Comprehensiv2

Accumulated Other Comprehensive Loss (Narrative) (Details) (Millennium Pipeline Company, L.L.C [Member], USD $)	9 Months Ended	12 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Millennium Pipeline Company, L.L.C [Member]	'	'
Accumulated Other Comprehensive Loss [Line Items]	'	'
Other Comprehensive Income Unrecognized Gain Loss On Derivatives Arising During Period Net Of Tax	$16.90	$17.70
Debt Instrument, Maturity Date	1-Jun-25	'

Accumulated_Other_Comprehensiv3

Accumulated Other Comprehensive Loss (Components Of Accumulated Other Comprehensive Loss) (Details) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Accumulated Other Comprehensive Income (Loss) [Line Items]	'	'	'	'
Beginning Balance	($41.40)	($62)	($43.60)	($65.50)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	-0.6	0.3	0.2	0.6
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	0.4	1.3	1.8	4.5
Other Comprehensive Income (Loss), Net of Tax	-0.2	1.6	2	5.1
Ending Balance	-41.6	-60.4	-41.6	-60.4
Accumulated Net Unrealized Investment Gain (Loss) [Member]	'	'	'	'
Accumulated Other Comprehensive Income (Loss) [Line Items]	'	'	'	'
Beginning Balance	0.5	-0.7	-0.3	2.6
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	-0.5	1	0.5	-1.9
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	-0.1	-0.1	-0.3	-0.5
Other Comprehensive Income (Loss), Net of Tax	-0.6	0.9	0.2	-2.4
Ending Balance	-0.1	0.2	-0.1	0.2
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]	'	'	'	'
Accumulated Other Comprehensive Income (Loss) [Line Items]	'	'	'	'
Beginning Balance	-24.5	-27.2	-25.8	-28.6
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	0	-0.1	0.1	-0.1
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	0.6	0.7	1.8	2.1
Other Comprehensive Income (Loss), Net of Tax	0.6	0.6	1.9	2
Ending Balance	-23.9	-26.6	-23.9	-26.6
Accumulated Defined Benefit Plans Adjustment [Member]	'	'	'	'
Accumulated Other Comprehensive Income (Loss) [Line Items]	'	'	'	'
Beginning Balance	-17.4	-34.1	-17.5	-39.5
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	-0.1	-0.6	-0.4	2.6
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	-0.1	0.7	0.3	2.9
Other Comprehensive Income (Loss), Net of Tax	-0.2	0.1	-0.1	5.5
Ending Balance	($17.60)	($34)	($17.60)	($34)

Business_Segment_Information_N

Business Segment Information (Narrative) (Details)	9 Months Ended
Business Segment Information (Narrative) (Details)	Sep. 30, 2014
Segment Reporting [Abstract]	'
Primary business segments	3
Number of counties in which electric service provided by Electric Operations	20

Business_Segment_Information_S

Business Segment Information (Schedule Of Operating Income Derived From Revenues And Expenses By Segment) (Details) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Segment Reporting Information [Line Items]	'	'	'	'
Revenues	$1,123.90	$1,076.80	$4,779.50	$4,060.50
Consolidated Operating Income (Loss)	157.8	176.4	911.1	799.3
Gas Distribution Operations [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Revenues	411.9	409.5	2,594.10	2,127
Consolidated Operating Income (Loss)	0.8	-5	362.4	279.1
Gas Distribution Operations [Member] \| Unaffiliated [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Revenues	411.9	409.5	2,593.80	2,126.80
Gas Distribution Operations [Member] \| Intersegment [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Revenues	0	0	0.3	0.2
Columbia Pipeline Group Operations [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Revenues	317.6	282.7	1,006.70	857.9
Consolidated Operating Income (Loss)	94.4	98.7	357	321
Columbia Pipeline Group Operations [Member] \| Unaffiliated [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Revenues	285.7	251.3	900.2	752
Columbia Pipeline Group Operations [Member] \| Intersegment [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Revenues	31.9	31.4	106.5	105.9
Electric Operations [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Revenues	424.7	413.7	1,280.50	1,176.40
Consolidated Operating Income (Loss)	76.9	87.5	218.7	212.2
Electric Operations [Member] \| Unaffiliated [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Revenues	424.4	413.6	1,279.90	1,175.90
Electric Operations [Member] \| Intersegment [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Revenues	0.3	0.1	0.6	0.5
Corporate and Other [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Revenues	140	122	399.4	357.1
Consolidated Operating Income (Loss)	-14.3	-4.8	-27	-13
Corporate and Other [Member] \| Unaffiliated [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Revenues	1.9	2.4	5.6	5.8
Corporate and Other [Member] \| Intersegment [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Revenues	138.1	119.6	393.8	351.3
Eliminations [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Revenues	($170.30)	($151.10)	($501.20)	($457.90)

Supplemental_Cash_Flow_Informa2

Supplemental Cash Flow Information (Details) (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013
Supplemental Cash Flow [Line Items]	'	'
Capital expenditures included in current liabilities	$213.90	$202.70
Assets acquired under a capital lease	69.9	5.7
Cash paid for interest, net of interest capitalized amounts	375	359.4
Cash paid for income taxes	$12.20	$8.50