NiSource (NI) 10-K/A 8 May 17 2016 FY Annual report (amended) Financial data

Document And Entity Information

Document And Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2016	Feb. 14, 2017	Jun. 30, 2016
Document Information [Line Items]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2016
Document Fiscal Year Focus	2,016
Document Fiscal Period Focus	FY
Entity Registrant Name	NISOURCE INC/DE
Entity Central Index Key	1,111,711
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float			$ 8,497,589,485
Entity Common Stock, Shares Outstanding		323,445,821

Statements Of Consolidated Inco

Statements Of Consolidated Income - USD ($) shares in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Net Revenues
Gas Distribution	$ 1,850.9	$ 2,081.9	$ 2,597.8
Gas Transportation and Storage	964.6	969.8	987.4
Electric	1,660.8	1,572.9	1,672
Other	16.2	27.2	15.2
Gross Revenues	4,492.5	4,651.8	5,272.4
Cost of Sales (excluding depreciation and amortization)	1,390.2	1,643.7	2,372.9
Total Net Revenues	3,102.3	3,008.1	2,899.5
Operating Expenses
Operation and maintenance	1,453.7	1,426.1	1,367.3
Depreciation and amortization	547.1	524.4	486.9
Gain (Loss) on sale of assets and impairments, net	(1)	1.6	3
Other taxes	244.3	256.1	253.2
Total Operating Expenses	2,244.1	2,208.2	2,110.4
Operating Income	858.2	799.9	789.1
Other Income (Deductions)
Interest expense, net	(349.5)	(380.2)	(379.5)
Other, net	1.5	17.4	13.4
Loss on early extinguishment of long-term debt	0	(97.2)	0
Total Other Deductions	(348)	(460)	(366.1)
Income from Continuing Operations before Income Taxes	510.2	339.9	423
Income Taxes	182.1	141.3	166.8
Income from Continuing Operations	328.1	198.6	256.2
Income (Loss) from Discontinued Operations - net of taxes	3.4	103.5	273.8
Net Income	331.5	302.1	530
Less: Net income attributable to noncontrolling interest	0	15.6	0
Net Income	331.5	286.5	530
Income from Discontinued Operations - net of taxes	$ 3.4	$ 87.9	$ 273.8
Basic Earnings Per Share
Continuing Operations	$ 1.02	$ 0.63	$ 0.81
Discontinued operations	0.01	0.27	0.87
Basic Earnings Per Share	1.03	0.90	1.68
Diluted Earnings Per Share
Continuing operations	1.01	0.63	0.81
Discontinued operations	0.01	0.27	0.86
Diluted Earnings Per Share	$ 1.02	$ 0.90	$ 1.67
Basic Average Common Shares Outstanding	321,805	317,746	315,120
Diluted Average Common Shares	323,524	319,836	316,636

Statements of Consolidated Comp

Statements of Consolidated Comprehensive Income - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Net Income		$ 331.5	$ 302.1	$ 530
Other comprehensive income (loss):
Net unrealized gain (loss) on available-for-sale securities	[1]	(0.1)	(0.8)	0.6
Net unrealized gain (loss) on cash flow hedges	[2]	8.6	(7.8)	2.2
Unrecognized pension and OPEB benefit (costs)	[3]	1.5	(2.4)	(9.8)
Total other comprehensive income (loss)		10	(11)	(7)
Total Comprehensive Income		341.5	291.1	523
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest		0	15.6	0
Total comprehensive income		$ 341.5	$ 275.5	$ 523
[1]	Net unrealized gain (loss) on available-for-sale securities, net of $0.1 million tax benefit, $0.4 million tax benefit and $0.3 million tax expense in 2016, 2015 and 2014, respectively.
[2]	Net unrealized gain (loss) on derivatives qualifying as cash flow hedges, net of $5.6 million tax expense, $4.8 million tax benefit and $1.5 million tax expense in 2016, 2015 and 2014, respectively.
[3]	Unrecognized pension and OPEB benefit (costs), net of $0.1 million tax expense, $4.6 million tax benefit and $2.5 million tax benefit in 2016, 2015 and 2014, respectively.

Statements of Consolidated Com4

Statements of Consolidated Comprehensive Income (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Tax	$ (0.1)	$ (0.4)	$ 0.3
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Tax	5.6	(4.8)	1.5
Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Tax	$ (0.1)	$ 4.6	$ 2.5

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment
Utility Plant	$ 19,368	$ 18,946.9
Accumulated depreciation and amortization	(6,613.7)	(6,853.4)
Net utility plant	12,754.3	12,093.5
Other property, at cost, less accumulated depreciation	313.7	18
Net Property, Plant and Equipment	13,068	12,111.5
Investments and Other Assets
Unconsolidated affiliates	6.6	6.9
Other investments	193.3	187.7
Total Investments and Other Assets	199.9	194.6
Current Assets
Cash and cash equivalents	26.4	15.5
Restricted cash	9.6	29.7
Accounts receivable (less reserve of $23.3 and $20.3, respectively)	847	660
Gas inventory	279.9	343.5
Materials and supplies, at average cost	101.7	86.8
Electric production fuel, at average cost	112.8	106.3
Exchange gas receivable	5.4	21
Regulatory assets	248.7	206.9
Prepayments and other	130.6	107.5
Total Current Assets	1,762.1	1,577.2
Other Assets
Regulatory assets	1,636.7	1,599.8
Goodwill	1,690.7	1,690.7
Intangible assets	242.7	253.7
Deferred charges and other	91.8	65
Total Other Assets	3,661.9	3,609.2
Total Assets	18,691.9	17,492.5
Common Stockholders' Equity
Common stock - $0.01 par value, 400,000,000 shares authorized; 323,159,672 and 319,110,083 shares outstanding, respectively	3.3	3.2
Treasury stock	(88.7)	(79.3)
Additional paid-in capital	5,153.9	5,078
Retained deficit	(972.2)	(1,123.3)
Accumulated other comprehensive loss	(25.1)	(35.1)
Total Common Stockholders' Equity	4,071.2	3,843.5
Long-term debt, excluding amounts due within one year	6,058.2	5,948.5
Total Capitalization	10,129.4	9,792
Current Liabilities
Current portion of long-term debt	363.1	433.7
Short-term borrowings	1,488	567.4
Accounts payable	539.4	433.4
Customer deposits and credits	264.1	316.3
Taxes accrued	195.4	183.5
Interest accrued	120.3	129
Exchange gas payable	83.7	62.3
Regulatory liabilities	116.7	231.4
Legal and environmental	37.4	37.6
Accrued compensation and employee benefits	161.4	141.3
Other accruals	82.7	121.6
Total Current Liabilities	3,452.2	2,657.5
Other Liabilities
Risk management liabilities	44.5	22.6
Deferred income taxes	2,528	2,365.3
Deferred investment tax credits	13.4	14.8
Accrued insurance liabilities	82.8	87.2
Accrued liability for postretirement and postemployment benefits	713.4	759.7
Regulatory liabilities	1,265.1	1,350.4
Asset retirement obligations	262.6	254
Other noncurrent liabilities	200.5	189
Total Other Liabilities	5,110.3	5,043
Commitments and Contingencies (Refer to Note 18, Other Commitments and Contingencies)	0	0
Total Capitalization and Liabilities	$ 18,691.9	$ 17,492.5

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Accounts receivable less reserve	$ 23.3	$ 20.3
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	400,000,000	400,000,000
Common stock, shares outstanding	323,159,672	319,110,083

Statements Of Consolidated Cash

Statements Of Consolidated Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Net Income	$ 331.5	$ 302.1	$ 530
Adjustments to Reconcile Net Income to Net Cash from Continuing Operations:
Loss on early extinguishment of debt	0	97.2	0
Depreciation and amortization	547.1	524.4	486.9
Deferred income taxes and investment tax credits	182.3	135.3	161.4
Stock compensation expense and 401(k) profit sharing contribution	46.5	50.7	66
Income from discontinued operations - net of taxes	(3.4)	(103.5)	(273.8)
Amortization of discount/premium on debt	7.6	8.7	10
AFUDC equity	(11.6)	(11.5)	(10.7)
Other adjustments	(3.8)	13.1	6.3
Changes in Assets and Liabilities:
Accounts receivable	(188)	262.2	(42.8)
Inventories	38.9	46.9	(115.9)
Accounts payable	108.8	(190.5)	29.9
Customer deposits and credits	(52.3)	35.5	29.8
Taxes accrued	12.1	8.7	4.5
Interest accrued	(8.7)	(11.6)	4.3
Exchange gas receivable/payable	36.9	(31.7)	(43.9)
Other accruals	(6)	(55.1)	4.4
Prepayments and other current assets	(0.4)	0.1	(2.2)
Regulatory assets/liabilities	(187.9)	82	(227.7)
Postretirement and postemployment benefits	(44.8)	25.6	136
Deferred charges and other noncurrent assets	(1.2)	5.2	3.9
Other noncurrent liabilities	0.5	(30.4)	4.8
Net Operating Activities from Continuing Operations	804.1	1,163.4	761.2
Net Operating Activities from (used for) Discontinued Operations	(0.8)	293.4	558.4
Net Cash Flows from Operating Activities	803.3	1,456.8	1,319.6
Net Cash Provided by (Used in) Investing Activities [Abstract]
Capital expenditures	(1,475.2)	(1,360.7)	(1,282.5)
Restricted cash withdrawals (deposits)	20.1	(4.8)	(17.1)
Cash Contributions from Spin Off	0	3,798.2	0
Cost of removal	(110.1)	(79.2)	(46.5)
Other investing activities	(17.7)	21.5	32.6
Net Investing Activities from (used for) Continuing Operations	(1,582.9)	2,375	(1,313.5)
Net Investing Activities used for Discontinued Operations	0	(430.1)	(803.1)
Net Cash Flows from (used for) Investing Activities	(1,582.9)	1,944.9	(2,116.6)
Net Cash Provided by (Used in) Financing Activities [Abstract]
Cash of CPG at Separation	0	(136.8)	0
Issuance of long-term debt	500	0	748.4
Repayments of long-term debt and capital lease obligations	(434.6)	(2,092.2)	(521)
Premiums and other debt related costs	(3.7)	(93.5)	(8.7)
Change in short-term borrowings, net	920.6	(936.4)	878.1
Issuance of common stock	23.1	22.5	30.3
Acquisition of treasury stock	(9.4)	(20.4)	(10.2)
Dividends paid - common stock	(205.5)	(263.4)	(321.3)
Net Financing Activities from (used for) Continuing Operations	790.5	(3,520.2)	795.6
Net Financing Activities from Discontinued Operations	0	108.6	0
Net Cash Flows from (used for) Financing Activities	790.5	(3,411.6)	795.6
Change in cash and cash equivalents from continuing operations	11.7	18.2	243.3
Change in cash and cash equivalents used for discontinued operations	(0.8)	(28.1)	(244.7)
Change in cash included in discontinued operations	0	0.5	(0.2)
Cash and cash equivalents at beginning of period	15.5	24.9	26.5
Cash and cash equivalents at beginning of period	$ 26.4	$ 15.5	$ 24.9

Statements Of Consolidated Comm

Statements Of Consolidated Common Stockholders' Equity - USD ($) $ in Millions		Total	Common Stock	Treasury Stock	Additional Paid-in Capital	Retained Deficit	Accumulated Other Comprehensive Loss
Beginning Balance at Dec. 31, 2013		$ 5,886.6	$ 3.2	$ (48.6)	$ 4,690.1	$ 1,285.5	$ (43.6)
Comprehensive Income (Loss):
Net Income		530	0	0	0	530	0
Other comprehensive loss, net of tax		(7)	0	0	0	0	(7)
Dividends:
Common stock		(321.5)	0	0	0	(321.5)	0
Treasury stock acquired		(10.3)	0	(10.3)	0	0	0
Stock issuances:
Employee stock purchase plan		4.2	0	0	4.2	0	0
Long-term incentive plan		40.2	0	0	40.2	0	0
401(k) and profit sharing		45.3	0	0	45.3	0	0
Dividend reinvestment plan		7.8	0	0	7.8	0	0
Ending Balance at Dec. 31, 2014		6,175.3	3.2	(58.9)	4,787.6	1,494	(50.6)
Comprehensive Income (Loss):
Net Income		286.5	0	0	0	286.5	0
Other comprehensive loss, net of tax		(11)	0	0	0	0	(11)
Allocation of AOCI to Noncontrolling Interest	[1]	2	0	0	0	0	2
Sale of interest in Columbia OpCo to CPPL	[1],[2]	227.1	0	0	227.1	0	0
Dividends:
Common stock		(263.5)	0	0	0	(263.5)	0
Distribution of CPG stock to shareholders		(2,615.8)	0	0	0	(2,640.3)	24.5
Treasury stock acquired		(20.4)	0	(20.4)	0	0	0
Stock issuances:
Employee stock purchase plan		5.1	0	0	5.1	0	0
Long-term incentive plan		4.2	0	0	4.2	0	0
401(k) and profit sharing		46.7	0	0	46.7	0	0
Dividend reinvestment plan		7.3	0	0	7.3	0	0
Ending Balance at Dec. 31, 2015		3,843.5	3.2	(79.3)	5,078	(1,123.3)	(35.1)
Dividends:
Cumulative effect of change in accounting principle		25.3	0	0	0	25.3	0
Net Income		331.5	0	0	0	331.5	0
Other comprehensive loss, net of tax		10	0	0	0	0	10
Common stock		(205.7)	0	0	0	(205.7)	0
Treasury stock acquired		(9.4)	0	(9.4)	0	0	0
Stock issuances:
Common stock		0.1	0.1	0	0	0	0
Employee stock purchase plan		4.7	0	0	4.7	0	0
Long-term incentive plan		20.9	0	0	20.9	0	0
401(k) and profit sharing		41.4	0	0	41.4	0	0
Dividend reinvestment plan		8.9	0	0	8.9	0	0
Ending Balance at Dec. 31, 2016		$ 4,071.2	$ 3.3	$ (88.7)	$ 5,153.9	$ (972.2)	$ (25.1)
[1]	This transaction, which occurred prior to the Separation, was distributed through retained earnings as part of the Separation on July 1, 2015.
[2]	Represents the purchase of an additional 8.4% limited partner interest in Columbia OpCo by an affiliate of CPG, recorded at the historical carrying value of Columbia OpCo's net assets after giving effect to the $1,168.4 million equity contribution from CPPL's IPO completed on February 11, 2015.

Statements Of Consolidated Com9

Statements Of Consolidated Common Stockholders' Equity (Shares) (Parenthetical) - USD ($) shares in Thousands, $ in Millions	Feb. 11, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Beginning Balance		319,110	316,037	313,676
Treasury stock acquired		(433)	(472)	(292)
Issued:
Employee stock purchase plan		201	203	113
Long-term incentive plan		2,103	1,423	1,125
Dividend reinvestment		386	275	206
Retirement savings plan		1,793	1,644	1,209
Ending Balance		323,160	319,110	316,037
Proceeds from Issuance Initial Public Offering	$ 1,168.4
Limited Liability Company (LLC) or Limited Partnership (LP), Members or Limited Partners, Ownership Interest	8.40%
Common Stock, Dividends, Per Share, Declared		$ 0.64	$ 0.83	$ 1.02
Common Stock
Beginning Balance		322,181	318,636	315,983
Issued:
Employee stock purchase plan		201	203	113
Long-term incentive plan		2,103	1,423	1,125
Dividend reinvestment		386	275	206
Retirement savings plan		1,793	1,644	1,209
Ending Balance		326,664	322,181	318,636
Treasury Stock
Beginning Balance		3,071	2,599	2,307
Treasury stock acquired		(433)	(472)	(292)
Issued:
Employee stock purchase plan		0	0	0
Long-term incentive plan		0	0	0
Dividend reinvestment		0	0	0
Retirement savings plan		0	0	0
Ending Balance		3,504	3,071	2,599

Nature of Operations And Summar

Nature of Operations And Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2016
Nature of Operations And Summary of Significant Accounting Policies [Abstract]
Nature of Operations and Summary of Significant Accounting Policies	Nature of Operations and Summary of Significant Accounting Policies A. Company Structure and Principles of Consolidation . NiSource, a Delaware corporation headquartered in Merrillville, Indiana, is an energy holding company whose subsidiaries are fully regulated natural gas and electric utility companies serving approximately 3.9 million customers in seven states. NiSource generates substantially all of its operating income through these rate-regulated businesses. The consolidated financial statements include the accounts of NiSource and its majority-owned subsidiaries after the elimination of all intercompany accounts and transactions. B. Use of Estimates. The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. C. Cash, Cash Equivalents and Restricted Cash . NiSource considers all highly liquid investments with original maturities of three months or less to be cash equivalents. NiSource reports amounts deposited in brokerage accounts for margin requirements as restricted cash. In addition, NiSource has amounts deposited in trust to satisfy requirements for the provision of various property, liability, workers compensation, and long-term disability insurance, which is classified as restricted cash and disclosed as an investing cash flow on the Statements of Consolidated Cash Flows. D. Accounts Receivable and Unbilled Revenue. Accounts receivable on the Consolidated Balance Sheets includes both billed and unbilled amounts. Unbilled amounts of accounts receivable relate to a portion of a customer’s consumption of gas or electricity from the date of the last cycle billing date through the last day of the month (balance sheet date). Factors taken into consideration when estimating unbilled revenue include historical usage, customer rates and weather. Accounts receivable fluctuates from year to year depending in large part on weather impacts and price volatility. NiSource's accounts receivable on the Consolidated Balance Sheets include unbilled revenue, less reserves, in the amounts of $329.7 million and $237.1 million as of December 31, 2016 and 2015, respectively. The reserve for uncollectible receivables is the Company’s best estimate of the amount of probable credit losses in the existing accounts receivable. The Company determined the reserve based on historical experience and in consideration of current market conditions. Account balances are charged against the allowance when it is anticipated the receivable will not be recovered. E. Investments in Debt Securities. NiSource’s investments in debt securities are carried at fair value and are designated as available-for-sale. These investments are included within “Other investments” on the Consolidated Balance Sheets. Unrealized gains and losses, net of deferred income taxes, are reflected as accumulated other comprehensive income (loss). These investments are monitored for other than temporary declines in market value. Realized gains and losses and permanent impairments are reflected in the Statements of Consolidated Income. No material impairment charges were recorded for the years ended December 31, 2016 , 2015 or 2014 . Refer to Note 16, "Fair Value," for additional information. F. Basis of Accounting for Rate-Regulated Subsidiaries . Rate-regulated subsidiaries account for and report assets and liabilities consistent with the economic effect of the way in which regulators establish rates, if the rates established are designed to recover the costs of providing the regulated service and it is probable that such rates can be charged and collected. Certain expenses and credits subject to utility regulation or rate determination normally reflected in income are deferred on the Consolidated Balance Sheets and are recognized in income as the related amounts are included in customer rates and recovered from or refunded to customers. In the event that regulation significantly changes the opportunity for NiSource to recover its costs in the future, all or a portion of NiSource’s regulated operations may no longer meet the criteria for regulatory accounting. In such an event, a write-down of all or a portion of NiSource’s existing regulatory assets and liabilities could result. If transition cost recovery was approved by the appropriate regulatory bodies that would meet the requirements under GAAP for continued accounting as regulatory assets and liabilities during such recovery period, the regulatory assets and liabilities would be reported at the recoverable amounts. If unable to continue to apply the provisions of regulatory accounting, NiSource would be required to apply the provisions of ASC 980-20, Discontinuation of Rate-Regulated Accounting . In management’s opinion, NiSource’s regulated subsidiaries will be subject to regulatory accounting for the foreseeable future. Refer to Note 8, "Regulatory Matters," for additional information. G. Plant and Other Property and Related Depreciation and Maintenance . Property, plant and equipment (principally utility plant) is stated at cost. The rate-regulated subsidiaries record depreciation using composite rates on a straight-line basis over the remaining service lives of the electric, gas and common properties as approved by the appropriate regulators. Non-utility property is generally depreciated on a straight-line basis over the life of the associated asset. Refer to Note 5, "Property, Plant and Equipment," for additional information related to depreciation expense at Units 7 and 8 at Bailly Generating Station. For rate-regulated companies, AFUDC is capitalized on all classes of property except organization costs, land, autos, office equipment, tools and other general property purchases. The allowance is applied to construction costs for that period of time between the date of the expenditure and the date on which such project is placed in service. The pre-tax rate for AFUDC was 4.5% in 2016 , 4.7% in 2015 and 4.5% in 2014 . Generally, NiSource’s subsidiaries follow the practice of charging maintenance and repairs, including the cost of removal of minor items of property, to expense as incurred. When NiSource’s subsidiaries retire regulated property, plant and equipment, original cost plus the cost of retirement, less salvage value, is charged to accumulated depreciation. However, when it becomes probable a regulated asset will be retired substantially in advance of its original expected useful life or is abandoned, the cost of the asset and the corresponding accumulated depreciation is recognized as a separate asset. If the asset is still in operation, the net amount is classified as "Other property, at cost, less accumulated depreciation" on the Consolidated Balance Sheets. If the asset is no longer operating, the net amount is classified in "Regulatory assets" on the Consolidated Balance Sheets. If NiSource is able to recover a full return on investment, the carrying value of the asset is based on historical cost. If NiSource is not able to recover a full return on investment, a loss on impairment is recognized to the extent the net book value of the asset exceeds the present value of future revenues discounted at the incremental borrowing rate. When NiSource’s subsidiaries sell entire regulated operating units, or retire or sell nonregulated properties, the original cost and accumulated depreciation and amortization balances are removed from "Property, Plant and Equipment" on the Consolidated Balance Sheets. Any gain or loss is recorded in earnings, unless otherwise required by the applicable regulatory body. Refer to Note 5, "Property, Plant and Equipment," for further information. External and internal costs associated with computer software developed for internal use are capitalized. Capitalization of such costs commences upon the completion of the preliminary stage of each project. Once the installed software is ready for its intended use, such capitalized costs are amortized on a straight-line basis generally over a period of five years, except for certain significant enterprise-wide technology investments which are amortized over a ten-year period. H. Goodwill and Other Intangible Assets. Substantially all of NiSource's goodwill relates to the excess of cost over the fair value of the net assets acquired in the Columbia acquisition on November 1, 2000. NiSource tests its goodwill for impairment annually as of May 1st, or more frequently if events and circumstances indicate that goodwill might be impaired. Fair value of NiSource's reporting units is determined using a combination of income and market approaches. NiSource has other intangible assets consisting primarily of franchise rights apart from goodwill that were identified as part of the purchase price allocations associated with the acquisition of Columbia of Massachusetts which is being amortized on a straight-line basis over forty years from the date of acquisition. See Note 6, "Goodwill and Other Intangible Assets," for additional information. I. Revenue Recognition. Revenue is recorded as products and services are delivered. Utility revenues are billed to customers monthly on a cycle basis. Revenues are recorded on the accrual basis and also include estimates for electricity and gas delivered but not billed. The accruals for unbilled revenues are reversed in the subsequent accounting period when meters are actually read and customers are billed. On occasion, NiSource's regulated subsidiaries are permitted to implement new rates that have not been formally approved by their state regulatory commissions, which are subject to refund. As permitted by accounting principles generally accepted in the United States, each regulated subsidiary recognizes this revenue and establishes a reserve for amounts that could be refunded based on its experience for the jurisdiction in which the rates were implemented. In connection with such revenues, estimated rate refund liabilities are recorded which reflect management’s current judgment of the ultimate outcomes of the proceedings. No provisions are made when, in the opinion of management, the facts and circumstances preclude a reasonable estimate of the outcome. J. Accounts Receivable Transfer Program. Certain of NiSource’s subsidiaries have agreements with third parties to sell certain accounts receivable without recourse. These transfers of accounts receivable are accounted for as secured borrowings. The entire gross receivables balance remains on the December 31, 2016 and 2015 Consolidated Balance Sheets and short-term debt is recorded in the amount of proceeds received from the purchasers involved in the transactions. Refer to Note 17, "Transfers of Financial Assets," for further information. K. Gas Cost and Fuel Adjustment Clause. NiSource’s regulated subsidiaries defer most differences between gas and fuel purchase costs and the recovery of such costs in revenues, and adjust future billings for such deferrals on a basis consistent with applicable state-approved tariff provisions. These deferred balances are recorded as regulatory assets or regulatory liabilities, as appropriate, on the Consolidated Balance Sheets. Refer to Note 8, "Regulatory Matters," for additional information. L. Inventory. Both the LIFO inventory methodology and the weighted average cost methodology are used to value natural gas in storage, as approved by regulators for all of NiSource’s regulated subsidiaries. Inventory valued using LIFO was $46.1 million and $50.2 million at December 31, 2016 and 2015 , respectively. Based on the average cost of gas using the LIFO method, the estimated replacement cost of gas in storage was less than the stated LIFO cost by $9.4 million and $27.2 million at December 31, 2016 and 2015 , respectively. Gas inventory valued using the weighted average cost methodology was $233.8 million at December 31, 2016 and $293.3 million at December 31, 2015 . Electric production fuel is valued using the weighted average cost inventory methodology, as approved by NIPSCO's regulator. Electric production fuel balances were $112.8 million at December 31, 2016 and $106.3 million at December 31, 2015 . Materials and supplies are valued using the weighted average cost inventory methodology. Materials and supplies balances were $101.7 million at December 31, 2016 and $86.8 million at December 31, 2015 . M. Accounting for Exchange and Balancing Arrangements of Natural Gas. NiSource’s Gas Distribution Operations segment enters into balancing and exchange arrangements of natural gas as part of its operations and off-system sales programs. NiSource records a receivable or payable for any of its respective cumulative gas imbalances, as well as for any gas inventory borrowed or lent under a Gas Distributions Operations exchange agreement. These receivables and payables are recorded as “Exchange gas receivable” or “Exchange gas payable” on NiSource’s Consolidated Balance Sheets, as appropriate. N. Accounting for Risk Management Activities. NiSource accounts for its derivatives and hedging activities in accordance with ASC 815. NiSource recognizes all derivatives as either assets or liabilities on the Consolidated Balance Sheets at fair value, unless such contracts are exempted as a normal purchase normal sale under the provisions of the standard. The accounting for changes in the fair value of a derivative depends on the intended use of the derivative and resulting designation. NiSource has elected not to net fair value amounts for any of its derivative instruments or the fair value amounts recognized for its right to receive cash collateral or obligation to pay cash collateral arising from those derivative instruments recognized at fair value, which are executed with the same counterparty under a master netting arrangement. See Note 9, "Risk Management Activities," for additional information. O. Income Taxes and Investment Tax Credits. NiSource records income taxes to recognize full interperiod tax allocations. Under the asset and liability method, deferred income taxes are provided for the tax consequences of temporary differences by applying enacted statutory tax rates applicable to future years to differences between the financial statement carrying amount and the tax basis of existing assets and liabilities. Previously recorded investment tax credits of the regulated subsidiaries were deferred on the balance sheet and are being amortized to book income over the regulatory life of the related properties to conform to regulatory policy. To the extent certain deferred income taxes of the regulated companies are recoverable or payable through future rates, regulatory assets and liabilities have been established. Regulatory assets for income taxes are primarily attributable to property-related tax timing differences for which deferred taxes had not been provided in the past, when regulators did not recognize such taxes as costs in the ratemaking process. Regulatory liabilities for income taxes are primarily attributable to the regulated companies’ obligation to refund to ratepayers deferred income taxes provided at rates higher than the current Federal income tax rate. Such amounts are credited to ratepayers using either the average rate assumption method or the reverse South Georgia method. Pursuant to the U.S. Internal Revenue Code and relevant state taxing authorities, NiSource and its subsidiaries file consolidated income tax returns for Federal and certain state jurisdictions. NiSource and its subsidiaries are parties to an agreement (the “Intercompany Income Tax Allocation Agreement”) that provides for the allocation of consolidated tax liabilities. The Intercompany Income Tax Allocation Agreement generally provides that each party is allocated an amount of tax similar to that which would be owed had the party been separately subject to tax. P. Environmental Expenditures. NiSource accrues for costs associated with environmental remediation obligations when the incurrence of such costs is probable and the amounts can be reasonably estimated, regardless of when the expenditures are actually made. The undiscounted estimated future expenditures are based on currently enacted laws and regulations, existing technology and estimated site-specific costs where assumptions may be made about the nature and extent of site contamination, the extent of cleanup efforts, costs of alternative cleanup methods and other variables. The liability is adjusted as further information is discovered or circumstances change. The reserves for estimated environmental expenditures are recorded on the Consolidated Balance Sheets in “Legal and environmental” for short-term portions of these liabilities and “Other noncurrent liabilities” for the respective long-term portions of these liabilities. Rate-regulated subsidiaries applying regulatory accounting establish regulatory assets on the Consolidated Balance Sheets to the extent that future recovery of environmental remediation costs is probable through the regulatory process. Refer to Note 18, "Other Commitments and Contingencies," for further information. Q. Excise Taxes. NiSource accounts for excise taxes that are customer liabilities by separately stating on its invoices the tax to its customers and recording amounts invoiced as liabilities payable to the applicable taxing jurisdiction. Such balances are presented within "Other accruals" on the Consolidated Balance Sheets. These types of taxes collected from customers, comprised largely of sales taxes, are presented on a net basis affecting neither revenues nor cost of sales. NiSource accounts for excise taxes for which it is liable by recording a liability for the expected tax with a corresponding charge to “Other taxes” expense on the Statements of Consolidated Income. R. Accrued Insurance Liabilities. NiSource accrues for insurance costs related to workers compensation, automobile, property, general and employment practices liabilities based on the most probable value of each claim. Claim values are determined by professional, licensed loss adjusters who consider the facts of the claim, anticipated indemnification and legal expenses, and respective state rules. Claims are reviewed by NiSource at least quarterly and an adjustment is made to the accrual based on the most current information. NiSource’s actual exposure to liability is minimal due to coverage from its wholly-owned captive insurer who then re-insures risk to third party insurance providers for the majority of costs paid to claimants above NiSource's deductible.

Recent Accounting Pronouncement

Recent Accounting Pronouncements	12 Months Ended
	Dec. 31, 2016
Recent Accounting Pronouncements [Abstract]
Recent Accounting Pronouncements	Recent Accounting Pronouncements Recently Issued Accounting Pronouncements NiSource is currently evaluating the impact of certain ASUs on its Consolidated Financial Statements or Notes to Consolidated Financial Statements, which are described below: Standard Description Effective date Effect on the financial statements or other significant matters ASU 2017-04, Intangibles - Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment The pronouncement simplifies the calculation of goodwill impairment charges by eliminating the the requirement to perform the "Step 2" analysis when the "Step 1" test is failed. Annual periods beginning after December 15, 2019, including interim periods therein. Early adoption is permitted for annual or interim periods beginning after January 1, 2017. NiSource elected to adopt this ASU effective January 1, 2017. The adoption of this standard did not have a material impact on the Consolidated Financial Statements or Notes to Consolidated Financial Statements. ASU 2016-18, Statement of Cash Flows (Topic 230): Restricted Cash (a consensus of the FASB Emerging Issues Task Force) The pronouncement provides clarification on the classification and presentation of restricted cash in the Statements of Consolidated Cash Flows. Annual periods beginning after December 15, 2017, including interim periods therein. Early adoption is permitted. Upon adoption, restricted cash on the Statements of Consolidated Cash Flows will no longer be presented as an investing activity and will instead be included as a component of beginning and ending cash. NiSource expects to adopt this ASU effective January 1, 2018. ASU 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments (a consensus of the Emerging Issues Task Force) The pronouncement provides specific guidance on eight cash flow classification issues to reduce the diversity in practice. Annual periods beginning after December 15, 2017, including interim periods therein. Early adoption is permitted. NiSource does not anticipate the adoption of this standard will have a material impact on the Consolidated Financial Statements or Notes to Consolidated Financial Statements. NiSource expects to adopt this ASU effective January 1, 2018. Standard Description Effective date Effect on the financial statements or other significant matters ASU 2016-13, Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments The pronouncement changes the impairment model for most financial assets, replacing the current "incurred loss" model. ASU 2016-13 will require the use of an "expected loss" model for instruments measured at amortized cost and will also require entities to record allowances for available-for-sale debt securities rather than reduce the carrying amount. Annual periods beginning after December 15, 2019, including interim periods therein. Early adoption is permitted for annual or interim periods beginning after December 15, 2018. NiSource is currently evaluating the impact of adoption, if any, on the Consolidated Financial Statements and Notes to Consolidated Financial Statements. ASU 2016-12, Revenue from Contracts with Customers (Topic 606): Narrow-Scope Improvements and Practical Expedients The pronouncement clarifies implementation guidance in ASU 2014-09 on assessing collectability, noncash consideration and the presentation of sales and other similar taxes collected from customers. Annual periods beginning after December 15, 2017, including interim periods therein. Early adoption is permitted for annual or interim periods beginning after December 15, 2016. NiSource has formed an internal stakeholder group to promote information sharing and communication of the new requirements. Additionally, NiSource participates in an informal forum of industry peers where questions can be asked and interpretations of the new standard can be shared. NiSource has separated its various revenue streams into high-level categories, which will serve as the basis for accounting analysis and documentation as it relates to the pronouncement's impact on NiSource's revenues. Substantially all of NiSource’s revenues are tariff based, which NiSource believes will be in scope of ASC 606. NiSource expects to adopt this ASU effective January 1, 2018. As of December 31, 2016, NiSource has not concluded on a method of adoption. ASU 2016-08, Revenue from Contracts with Customers (Topic 606): Principal versus Agent Considerations The pronouncement clarifies the principal versus agent guidance in ASU 2014-09. The amendment clarifies how an entity should identify the unit of accounting for the principal versus agent evaluation, and how it should apply the control principle to certain types of arrangements. ASU 2014-09, Revenue from Contracts with Customers (Topic 606) The pronouncement 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. ASU 2016-02, Leases (Topic 842) The pronouncement introduces a lessee model that brings most leases on the balance sheet. The standard requires that lessees recognize the following for all leases (with the exception of short-term leases, as that term is defined in the standard) at the lease commencement date: (1) a lease liability, which is a lessee’s obligation to make lease payments arising from a lease, measured on a discounted basis; and (2) a right-of-use asset, which is an asset that represents the lessee’s right to use, or control the use of, a specified asset for the lease term. Annual periods beginning after December 15, 2018, including interim periods therein. Early adoption is permitted. NiSource has formed an internal stakeholder group that meets periodically to share information and gather data related to leasing activity at NiSource. This includes compiling a list of all contracts that could meet the definition of a lease under the new standard and evaluating the accounting for these contracts under the new standard to determine the ultimate impact the new standard will have on NiSource’s financial statements. Also this procedure has identified process improvements to ensure data from newly initiated leases is captured to comply with the new standard. This work is ongoing with the assistance of a third-party advisory firm. As of December 31, 2016, no conclusion has been reached as to when NiSource will adopt this standard. ASU 2016-01, Financial Instruments (Topic 825): Recognition and Measurement of Financial Assets and Financial Liabilities The pronouncement makes limited amendments to the guidance in GAAP on the classification and measurement of financial instruments. The standard requires entities to measure equity investments that do not result in consolidation and are not accounted for under the equity method at fair value and recognize any changes in fair value in net income unless the investments qualify for the new practicability exception. Annual periods beginning after December 15, 2017, including interim periods therein. Early adoption is permitted. NiSource is currently evaluating the impact of adoption, if any, on the Consolidated Financial Statements and Notes to Consolidated Financial Statements. Recently Adopted Accounting Pronouncements The table below includes ASUs NiSource adopted during 2016: Standard Adoption ASU 2016-09, Compensation-Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting NiSource elected to adopt this pronouncement during the third quarter of 2016. Upon adoption, NiSource elected to begin accounting for forfeitures of share-based awards as they occur. The impact of this change was not material. Additionally, NiSource recorded a $25.3 million credit to beginning retained deficit. This adjustment represents excess tax benefits generated in years prior to 2016 that were previously not recognized in stockholders' equity due to NOLs in those years. Both of these adjustments were adopted on a modified retrospective basis. Lastly, NiSource recorded income tax benefits of $7.2 million related to excess tax benefits generated in 2016. This provision was adopted on a prospective basis. However, because NiSource adopted the standard during an interim period, the standard required this $7.2 million benefit be reflected as though it was adopted as of January 1, 2016.

Discontinued Operations

Discontinued Operations	12 Months Ended
	Dec. 31, 2016
Discontinued Operations and Disposal Groups [Abstract]
Discontinued Operations	Discontinued Operations On July 1, 2015, NiSource completed the Separation through a special pro rata stock dividend, distributing one share of CPG common stock for every one share of NiSource common stock held by any NiSource stockholder on June 19, 2015, the record date. The Separation resulted in two stand-alone energy infrastructure companies: NiSource, a fully regulated natural gas and electric utilities company, and CPG, a natural gas pipeline, midstream and storage company. As a stand-alone company, on the date of the Separation, CPG's operations consisted of NiSource's Columbia Pipeline Group Operations segment prior to the Separation. Following the Separation, NiSource retained no ownership interest in CPG. On the date of the Separation, CPG consisted of approximately $9.2 billion of assets, $5.6 billion of liabilities and $3.6 billion of equity. The results of operations and cash flows for the former Columbia Pipeline Group Operations segment have been reported as discontinued operations for all periods presented. Additionally, the assets and liabilities of the former Columbia Pipeline Group Operations segment were reclassified as assets and liabilities of discontinued operations for all prior periods. During 2016, NiSource recorded a $3.6 million tax benefit resulting from favorable estimate-to-actual adjustments related to non-deductible costs from the Separation. There were no other material results from discontinued operations during 2016. Results from discontinued operations are provided in the following table. These results are primarily from NiSource's former Columbia Pipeline Group Operations segment. Year Ended December 31, 2015 (in millions) Columbia Pipeline Group Operations Corporate and Other Total Net Revenues Transportation and storage revenues $ 561.4 $ — $ 561.4 Other revenues 94.3 — 94.3 Total Sales Revenues 655.7 — 655.7 Less: Cost of sales (excluding depreciation and amortization) 0.2 — 0.2 Net Revenues 655.5 — 655.5 Operating Expenses Operation and maintenance 375.8 (1) — 375.8 Depreciation and amortization 66.4 — 66.4 Gain on sale of assets (13.6 ) — (13.6 ) Other taxes 38.0 — 38.0 Total Operating Expenses 466.6 — 466.6 Equity Earnings in Unconsolidated Affiliates 29.1 — 29.1 Operating Income from Discontinued Operations 218.0 — 218.0 Other Income (Deductions) Interest expense, net (37.1 ) — (37.1 ) Other, net 7.8 0.4 8.2 Total Other Income (Deductions) (29.3 ) 0.4 (28.9 ) Income from Discontinued Operations before Income Taxes 188.7 0.4 189.1 Income Taxes 84.7 0.9 85.6 Income (Loss) from Discontinued Operations - net of taxes $ 104.0 $ (0.5 ) $ 103.5 (1) Includes approximately $55.4 million of transaction costs related to the Separation. Year Ended December 31, 2014 (in millions) Columbia Pipeline Group Operations Corporate and Other Total Net Revenues Transportation and storage revenues $ 1,034.3 $ — $ 1,034.3 Other revenues 312.9 — 312.9 Total Sales Revenues 1,347.2 — 1,347.2 Less: Cost of sales (excluding depreciation and amortization) 0.3 — 0.3 Net Revenues 1,346.9 — 1,346.9 Operating Expenses Operation and maintenance 769.1 (1) — 769.1 Depreciation and amortization 118.6 — 118.6 Gain on sale of assets (34.5 ) — (34.5 ) Other taxes 67.1 — 67.1 Total Operating Expenses 920.3 — 920.3 Equity Earnings in Unconsolidated Affiliates 46.6 — 46.6 Operating Income from Discontinued Operations 473.2 — 473.2 Other Income (Deductions) Interest expense, net (64.1 ) — (64.1 ) Other, net 8.9 (1.0 ) 7.9 Total Other Income (Deductions) (55.2 ) (1.0 ) (56.2 ) Income (Loss) from Discontinued Operations before Income Taxes 418.0 (1.0 ) 417.0 Income Taxes 143.5 (0.3 ) 143.2 Income (Loss) from Discontinued Operations - net of taxes $ 274.5 $ (0.7 ) $ 273.8 (1) Includes approximately $23.7 million of transaction costs related to the Separation. CPG’s financing requirements prior to the private placement of senior notes on May 22, 2015 were satisfied through borrowings from NiSource Finance. Interest expense from discontinued operations primarily represents net interest charged to CPG from NiSource Finance, less AFUDC. Subsequent to May 22, 2015, interest expense from discontinued operations also includes interest incurred on CPG’s private placement of $2,750.0 million of senior notes. Continuing Involvement Natural gas transportation and storage services provided to NiSource by CPG were $ 150.5 million , $147.6 million and $146.2 million for the years ended December 31, 2016, 2015 and 2014, respectively. Prior to July 1, 2015, these costs were eliminated in consolidation. Beginning July 1, 2015, these costs and associated cash flows represent third-party transactions with CPG and are not eliminated in consolidation, as such services have continued subsequent to the Separation and are expected to continue for the foreseeable future. As a result of the Separation, NiSource and CPG entered into Transition Services Agreements ("TSAs"). NiSource expects the TSAs to terminate within 24 months from the date of the Separation. The TSAs set forth the terms and conditions for NiSource and CPG to provide certain transition services to one another. Under the TSAs, NiSource provides CPG certain information technology, financial and accounting, human resource and other specified services. For the period July 1, 2015 to December 31, 2015 and for the year ended December 31, 2016, the amounts NiSource billed CPG for these services were immaterial. There were no material assets and liabilities of discontinued operations on the Consolidated Balance Sheets at December 31, 2016 and 2015.

Earnings Per Share

Earnings Per Share	12 Months Ended
	Dec. 31, 2016
Earnings Per Share [Abstract]
Earnings Per Share	Earnings Per Share Basic EPS is computed by dividing net income attributable to NiSource 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 computation of diluted average common shares is as follows: Year Ended December 31, (in thousands) 2016 2015 2014 Denominator Basic average common shares outstanding 321,805 317,746 315,120 Dilutive potential common shares: Nonqualified stock options — — 6 Shares contingently issuable under employee stock plans 165 — 1,066 Shares restricted under stock plans 1,554 2,090 444 Diluted Average Common Shares 323,524 319,836 316,636

Property, Plant And Equipment

Property, Plant And Equipment	12 Months Ended
	Dec. 31, 2016
Property, Plant and Equipment [Abstract]
Property, Plant And Equipment	Property, Plant and Equipment NiSource’s property, plant and equipment on the Consolidated Balance Sheets are classified as follows: At December 31, (in millions) 2016 2015 Property Plant and Equipment Gas Distribution Utility (1) $ 11,556.6 $ 10,620.4 Electric Utility (1)(2) 7,043.3 7,765.7 Corporate 105.0 107.2 Construction Work in Process 663.1 453.6 Non-Utility and Other (2) 681.7 41.2 Total Property, Plant and Equipment $ 20,049.7 $ 18,988.1 Accumulated Depreciation and Amortization Gas Distribution Utility (1) $ (3,119.2 ) $ (3,029.0 ) Electric Utility (1)(2) (3,442.0 ) (3,767.7 ) Corporate (52.5 ) (56.7 ) Non-Utility and Other (2) (368.0 ) (23.2 ) Total Accumulated Depreciation and Amortization $ (6,981.7 ) $ (6,876.6 ) Net Property, Plant and Equipment $ 13,068.0 $ 12,111.5 (1) NIPSCO’s common utility plant and associated accumulated depreciation and amortization are allocated between Gas Distribution Utility and Electric Utility Property, Plant and Equipment. (2) Non-Utility and Other in 2016 primarily consists of Bailly Generating Station (Units 7 and 8) which were reclassified from Electric Utility in the fourth quarter of 2016. Depreciation expense for the remaining net book value will continue to be recorded at the composite depreciation rate most recently approved by the IURC. See Note 18-E, "Other Matters," for additional information. The weighted average depreciation provisions for utility plant, as a percentage of the original cost, for the periods ended December 31, 2016 , 2015 and 2014 were as follows: 2016 2015 2014 Electric Operations 3.3 % 3.1 % 3.0 % Gas Distribution Operations 2.1 % 2.0 % 2.1 % Amortization of Software Costs. NiSource amortized $41.4 million in 2016 , $41.1 million in 2015 and $33.7 million in 2014 related to software costs. NiSource’s unamortized software balance was $156.4 million and $167.1 million at December 31, 2016 and 2015 , respectively.

Goodwill And Other Intangible A

Goodwill And Other Intangible Assets	12 Months Ended
	Dec. 31, 2016
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill And Other Intangible Assets	Goodwill and Other Intangible Assets Goodwill. Substantially all of NiSource's goodwill relates to the excess of cost over the fair value of the net assets acquired in the Columbia acquisition on November 1, 2000. The following presents NiSource's goodwill balance allocated by segment as of December 31, 2016 : (in millions) Gas Distribution Operations Electric Operations Corporate and Other Total Goodwill $ 1,690.7 $ — $ — $ 1,690.7 NiSource completed a quantitative ("step 1") fair value measurement of its reporting units during the May 1, 2016 goodwill test. The test indicated that the fair value of each of the reporting units that are allocated goodwill exceeded their carrying values, indicating that no impairment was necessary. Intangible Assets. NiSource's intangible assets, apart from goodwill, consist of franchise rights. Franchise rights were identified as part of the purchase price allocations associated with the acquisition in February 1999 of Columbia of Massachusetts. These amounts were $242.7 million and $253.7 million , net of accumulated amortization of $199.5 million and $188.5 million , at December 31, 2016 and 2015 , respectively, and are being amortized on a straight-line basis over forty years from the date of acquisition through 2039. NiSource recorded amortization expense of $11.0 million in 2016 , 2015 , and 2014 related to its franchise right intangible asset.

Asset Retirement Obligations

Asset Retirement Obligations	12 Months Ended
	Dec. 31, 2016
Asset Retirement Obligation [Abstract]
Asset Retirement Obligations	Asset Retirement Obligations NiSource has recognized asset retirement obligations associated with various legal obligations including costs to remove and dispose of certain construction materials located within many of NiSource’s facilities, certain costs to retire pipeline, removal costs for certain underground storage tanks, removal of certain pipelines known to contain PCB contamination, closure costs for certain sites including ash ponds, solid waste management units and a landfill, as well as some other nominal asset retirement obligations. NiSource has a significant obligation associated with the decommissioning of its two hydro facilities located in Indiana. These hydro facilities have an indeterminate life, and as such, no asset retirement obligation has been recorded. Changes in NiSource’s liability for asset retirement obligations for the years 2016 and 2015 are presented in the table below: (in millions) 2016 2015 Beginning Balance $ 254.0 $ 136.2 Accretion recorded as a regulatory asset/liability 9.2 8.6 Additions — 6.5 Settlements (7.5 ) (7.0 ) Change in estimated cash flows 6.9 (1) 109.7 (2) Ending Balance $ 262.6 $ 254.0 (1) The change in estimated cash flows for 2016 is primarily attributed to the changes in estimated costs for retirement of gas mains partially offset by revisions to estimated costs associated with the EPA's final rule for regulation of CCRs and changes to cost estimates for certain solid waste management units. See Note 18-D, "Environmental Matters," for additional information on CCRs. (2) The change in estimated cash flows for 2015 primarily represents estimated costs associated with the EPA's final rule for regulation of CCRs and changes to cost estimates for certain solid waste management units. See Note 18-D, "Environmental Matters," for additional information on CCRs. Certain non-legal costs of removal that have been, and continue to be, included in depreciation rates and collected in the customer rates of the rate-regulated subsidiaries are classified as "Regulatory liabilities" on the Consolidated Balance Sheets.

Regulatory Matters

Regulatory Matters	12 Months Ended
	Dec. 31, 2016
Regulatory Assets and Liabilities Disclosure [Abstract]
Regulatory Matters	Regulatory Matters Regulatory Assets and Liabilities NiSource follows the accounting and reporting requirements of ASC Topic 980, which provides that regulated entities account for and report assets and liabilities consistent with the economic effect of regulatory rate-making procedures if the rates established are designed to recover the costs of providing the regulated service and it is probable that such rates can be charged and collected. Certain expenses and credits subject to utility regulation or rate determination normally reflected in income or expense are deferred on the balance sheet and are recognized in the income statement as the related amounts are included in customer rates and recovered from or refunded to customers. Regulatory assets were comprised of the following items: At December 31, (in millions) 2016 2015 Regulatory Assets Unrecognized pension benefit and other postretirement benefit costs (see Note 11) $ 847.5 $ 928.7 Other postretirement costs (see Note 11) 59.6 47.0 Environmental costs (see Note 18-D) 62.6 62.2 Regulatory effects of accounting for income taxes (see Note 1-O and Note 10) 238.4 234.1 Underrecovered gas and fuel costs (see Note 1-K) 73.5 34.8 Depreciation 136.8 124.5 Uncollectible accounts receivable deferred for future recovery 7.3 17.0 Post-in-service carrying charges 134.9 107.2 EERM operation and maintenance and depreciation deferral 54.1 48.1 Sugar Creek carrying charges and deferred depreciation 16.8 28.2 TDSIC 15.9 6.7 Safety Activity Costs 41.5 19.6 DSM Program 48.4 35.6 Other 148.1 113.0 Total Regulatory Assets $ 1,885.4 $ 1,806.7 Regulatory liabilities were comprised of the following items: At December 31, (in millions) 2016 2015 Regulatory Liabilities Overrecovered gas and fuel costs (see Note 1-K) $ 54.8 $ 148.1 Cost of removal (see Note 7) 1,174.5 1,261.5 Regulatory effects of accounting for income taxes (see Note 1-O and Note 10) 30.0 34.2 Other postretirement costs (see Note 11) 41.2 38.8 Other 81.3 99.2 Total Regulatory Liabilities $ 1,381.8 $ 1,581.8 Regulatory assets, including underrecovered gas and fuel cost, of approximately $1,708.2 million as of December 31, 2016 are not earning a return on investment. Regulatory assets of approximately $1,561.9 million include expenses that are recovered as components of the cost of service and are covered by regulatory orders. These costs are recovered over a remaining life of up to 41 years. Regulatory assets of approximately $323.5 million at December 31, 2016 , require specific rate action. As noted below, regulatory assets for which costs have been incurred are included (or expected to be included, for costs incurred subsequent to the most recently approved rate case) in certain companies’ rate base, thereby providing a return on invested costs. Certain regulatory assets do not result from cash expenditures and therefore do not represent investments included in rate base or have offsetting liabilities that reduce rate base. Assets: Unrecognized pension benefit and other postretirement benefit costs – In 2007, NiSource adopted certain updates of ASC 715 which required, among other things, the recognition in other comprehensive income or loss of the actuarial gains or losses and the prior service costs or credits that arise during the period but that are not immediately recognized as components of net periodic benefit costs. Certain subsidiaries defer these gains or losses as a regulatory asset in accordance with regulatory orders or as a result of regulatory precedent, to be recovered through base rates. Other postretirement costs – Primarily relates to the difference between postretirement expense recorded by certain subsidiaries due to regulatory orders and the postretirement expense recorded in accordance with GAAP. These costs are expected to be collected through future base rates, revenue riders or tracking mechanisms. Environmental costs – Includes certain recoverable costs of investigating, testing, remediating and other costs related to gas plant sites, disposal sites or other sites onto which material may have migrated. Certain companies defer the costs as a regulatory asset in accordance with regulatory orders, to be recovered in future base rates, billing riders or tracking mechanisms. Regulatory effects of accounting for income taxes – Represents the deferral and under collection of deferred taxes in the rate making process. In prior years, NiSource has lowered customer rates in certain jurisdictions for the benefits of accelerated tax deductions. Amounts are expensed for financial reporting purposes as NiSource recovers deferred taxes in the rate making process. Underrecovered gas and fuel costs – Represents the difference between the costs of gas and fuel and the recovery of such costs in revenue and is used to adjust future billings for such deferrals on a basis consistent with applicable state-approved tariff provisions. Recovery of these costs is achieved through tracking mechanisms. Depreciation – Primarily relates to the difference between the depreciation expense recorded by Columbia of Ohio due to a regulatory order and the depreciation expense recorded in accordance with GAAP. The regulatory asset is currently being amortized over the life of the assets. Also included is depreciation associated with the Columbia of Ohio IRP and capital expenditure program. Recovery of these costs is achieved through base rates and rider mechanisms. In 2005, the PUCO authorized Columbia of Ohio to revise its depreciation accrual rates for the period beginning January 1, 2005. The revised depreciation rates are now higher than those which would have been utilized if Columbia of Ohio were not subject to regulation. The amount of depreciation that would have been recorded for 2005 through 2016 had Columbia of Ohio not been subject to rate regulation is a combined $638.0 million , $74.1 million less than the $712.1 million reflected in rates. The regulatory asset was $57.6 million and $65.3 million as of December 31, 2016 and 2015 , respectively. The amount of depreciation that would have been recorded for 2016 had Columbia of Ohio not been subject to rate regulation is $78.2 million , $7.7 million less than the $85.9 million reflected in rates. Columbia of Ohio also has PUCO approval to defer depreciation associated with its IRP and capital expenditure program. As of December 31, 2016 , depreciation of $23.4 million and $31.8 million was deferred for the respective programs. Recovery of the IRP depreciation is approved annually through the IRP rider. The equivalent of annual depreciation expense, based on the average life of the related assets, is included in the calculation of the IRP rider approved by the PUCO and billed to customers. Deferred depreciation expense is recognized as the IRP rider is billed to customers. The recovery mechanism for depreciation associated with the capital expenditure program will be addressed in a separate rate proceeding. Uncollectible accounts receivable deferred for future recovery – Represents the difference between certain uncollectible expenses and the recovery of such costs to be collected through cost tracking mechanisms in accordance with regulatory orders. Post-in-service carrying charges – Columbia of Ohio has approval from the PUCO by regulatory order to defer debt-based carrying charges as a regulatory asset for future recovery. Columbia of Ohio defers this carrying charge on eligible property, plant and equipment from the time it is placed into utility service until recovery of the property, plant and equipment is included in customer rates in base rates or through a rider mechanism. Inclusion in customer rates generally occurs when Columbia of Ohio files its next rate proceeding following the in-service date of the property, plant and equipment. EERM operation and maintenance and depreciation deferral – NIPSCO obtained approval from the IURC to recover certain environmental related costs including operation and maintenance and depreciation expense once the environmental facilities become operational. Recovery of these costs will continue until such assets are included in rate base through an electric base rate case. The EERM deferred charges represent expenses that will be recovered from customers through an annual EERM Cost Tracker which authorizes the collection of deferred balances over a six month period. Sugar Creek carrying charges and deferred depreciation – The IURC approved the deferral of debt-based carrying charges and the deferral of depreciation expense for the Sugar Creek assets. Balances are being amortized over seven years with new rates implemented on October 1, 2016. TDSIC - NIPSCO obtained approval from the IURC to recover costs for certain system modernization projects outside of a base rate proceeding. Eighty percent of the related costs, including depreciation, property taxes, and debt and equity based carrying charges are recovered through a semi-annual recovery mechanism. Recovery of these costs will continue until such assets are included in rate base through a gas or electric rate case, respectively. The remaining twenty percent of the costs are deferred until the next rate case which includes a twenty percent deferral of the return on capital. Equity based carrying charges and the equity component of return on capital are not reflected in the regulatory asset balance at December 31, 2016. Safety Activity Costs - Represents the difference between costs incurred in eligible safety programs in excess of those being recovered in rates. The eligible cost deferrals represent necessary business expenses incurred in compliance with PHMSA regulations and are targeted to enhance the safety of the pipeline systems. Certain subsidiaries defer the excess costs as a regulatory asset in accordance with regulatory orders and recovery of these costs will be address in future base rate proceedings. DSM Program - Represents costs associated with Gas Distribution Operations and Electric Operations companies' energy efficiency and conservation programs. Costs are recovered through tracking mechanisms. Liabilities: Overrecovered gas and fuel costs – Represents the difference between the cost of gas and fuel and the recovery of such costs in revenues, and is the basis to adjust future billings for such refunds on a basis consistent with applicable state-approved tariff provisions. Refunding of these revenues is achieved through tracking mechanisms. Cost of removal – Represents anticipated costs of removal that have been, and continue to be, included in depreciation rates and collected in customer rates of the rate-regulated subsidiaries for future costs to be incurred. Regulatory effects of accounting for income taxes – Represents amounts owed to customers for deferred taxes collected at a higher rate than the current statutory rates and liabilities associated with accelerated tax deductions owed to customers that are established during the rate making process. Other postretirement costs – Primarily represents cash contributions in excess of postretirement benefit expense that is deferred as a regulatory liability by certain subsidiaries in accordance with regulatory orders. Gas Distribution Operations Regulatory Matters Cost Recovery and Trackers . 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 those described below. Increases in the expenses that are the subject of trackers result in a corresponding increase in net revenues and therefore have essentially no impact on total operating income results. 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 through 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, and bad debt recovery mechanisms. A portion of the distribution companies' revenue is related to the recovery of gas costs, the review and recovery of which occurs through standard regulatory proceedings. All states in NiSource's operating area 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 of the 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. Columbia of Ohio. On November 28, 2012, the PUCO approved Columbia of Ohio’s application to extend its Infrastructure Replacement Program for an additional five years (2013-2017), allowing Columbia of Ohio to continue to invest and recover on its accelerated main replacements. Columbia of Ohio last filed its application to adjust rates associated with its IRP and DSM Riders on February 26, 2016, which requested authority to increase revenues by $25.9 million . On April 20, 2016, the PUCO issued an order approving Columbia of Ohio’s application with rates going into effect April 30, 2016. On November 28, 2016, Columbia of Ohio filed its notice of intent to file an application to adjust rates associated with its IRP and DSM riders. The notice of intent states that Columbia of Ohio will file an application by February 28, 2017, in which it will request authority to increase revenues by up to $33.5 million . On December 27, 2016, Columbia of Ohio filed its Notice of Intent to file an application that will request authority for Columbia of Ohio to extend its IRP for an additional five years (2018-2022). Columbia of Ohio’s application will be filed in late February 2017. On December 17, 2014, the PUCO approved Columbia of Ohio’s application to establish a regulatory asset and defer the expenditures to be incurred in implementing Columbia of Ohio’s Pipeline Safety Program. Columbia of Ohio requested authority to defer Pipeline Safety Program costs of up to $15 million annually. On March 11, 2016, Columbia of Ohio filed an application to increase the annual deferral authority from $15 million to $25 million . On June 24, 2016, Columbia of Ohio and PUCO staff filed a stipulation that recommended approval of the application in all material respects. On August 26, 2016, the PUCO approved the stipulation to increase the deferral authority to $25 million per year through January 1, 2024. Columbia of Pennsylvania. On March 18, 2016, Columbia of Pennsylvania filed a base rate case with the Pennsylvania PUC, seeking a revenue increase of $55.3 million annually. The case was driven by Columbia of Pennsylvania’s ongoing capital investment program which exceeded $232.0 million in 2016, and is projected to exceed $267.0 million in 2017. This case was also driven by operation and maintenance expenditures related to employee training and compliance with pipeline safety regulations. Columbia of Pennsylvania's request for rate relief included the recovery of costs that will be incurred after the implementation of new rates, as authorized by the Pennsylvania General Assembly with the passage of Act 11 of 2012. On September 2, 2016, the parties to the case filed a joint petition for settlement which provides for an annual revenue increase of $35.0 million . On September 28, 2016, the assigned administrative law judge issued a recommended decision to approve the proposed settlement, without modification. An order approving the settlement was issued from the Pennsylvania PUC on October 27, 2016, and new rates went into effect on December 19, 2016. NIPSCO Gas. On April 30, 2013, then Indiana Governor Pence signed Senate Enrolled Act 560, the TDSIC statute, 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, eighty 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 twenty 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 December 28, 2016, the IURC issued an order on the seven-year plan (2014-2020) within TDSIC-5 approving NIPSCO’s updated estimate of TDSIC-eligible investments of $824 million . The order also included approval to begin recovery of $211.6 million of cumulative net capital spend through June 30, 2016. New rates went into effect on January 1, 2017. Columbia of Massachusetts. On July 7, 2014, the Governor of Massachusetts signed into law Chapter 149 of the Acts of 2014, An Act Relative to Natural Gas Leaks (“the Act”). The Act authorizes natural gas distribution companies to file gas infrastructure replacement plans with the Massachusetts DPU to address the replacement of aging natural gas pipeline infrastructure. In addition, the Act provides that the Massachusetts DPU may, after review of the plans, allow the proposed estimated costs of the plan into rates as of May 1 of the subsequent year. Pursuant to the Act, on October 30, 2015, Columbia of Massachusetts filed its GSEP for the 2016 construction year (“2016 GSEP”). Columbia of Massachusetts proposed to recover an increment of $6.4 million for the costs associated with the replacement of eligible leak-prone infrastructure during the 2016 construction year for a cumulative proposed revenue requirement recovery of $9.0 million . Columbia of Massachusetts subsequently revised the cumulative proposed revenue requirement recovery to $8.2 million . The Massachusetts DPU approved the 2016 GSEP filing on April 29, 2016, with new rates effective May 1, 2016. On October 31, 2016, Columbia of Massachusetts filed its GSEP for the 2017 construction year. Columbia of Massachusetts is proposing to recover an incremental $8.1 million for a cumulative revenue requirement recovery of $16.8 million . An order is expected from the Massachusetts DPU in early 2017, with new rates effective May 1, 2017. On October 30, 2009, the Massachusetts DPU approved Columbia of Massachusetts's revenue decoupling mechanism that was filed in its base rate case. This allows Columbia of Massachusetts to apply annual adjustments to its peak and off-peak rates. On March 16, 2016, Columbia of Massachusetts filed its 2016 off-peak period RDAF in the amount of $3.4 million . On April 28, 2016, the Massachusetts DPU approved the rate, which was effective May 1, 2016. On September 16, 2016, Columbia of Massachusetts filed its 2016-2017 peak period RDAF in the amount of $12.9 million . However, due to the implementation of the revenue cap included in the mechanism, $8.9 million is to be recovered starting November 1, 2016, with the remaining $4.0 million deferred until the 2017-2018 peak period RDAF. On October 31, 2016, the Massachusetts DPU approved the recovery of $8.9 million in rates effective November 1, 2016. On April 16, 2015, Columbia of Massachusetts filed a base rate case with the Massachusetts DPU. The case, which sought increased annual revenues of approximately $49.0 million , was designed to support Columbia of Massachusetts's continued focus on providing safe and reliable service in compliance with increasing state and federal regulations and oversight, and recovery of associated increased operations and maintenance costs. Columbia of Massachusetts arrived at a settlement agreement with the Massachusetts Attorney General in the case which was filed for approval with the Massachusetts DPU on August 19, 2015 and approved on October 7, 2015. The settlement agreement provides for increased annual revenues of $32.8 million beginning November 1, 2015, with an additional $3.6 million annual increase in revenues starting November 1, 2016. The settlement also provides that Columbia of Massachusetts cannot increase base distribution rates to become effective prior to November 1, 2018. Columbia of Virginia. On April 29, 2016, Columbia of Virginia filed a request with the VSCC, seeking an annual revenue increase of $37.0 million . The case is driven by Columbia of Virginia's ongoing capital program to modernize its infrastructure and to expand and upgrade its facilities to meet customer growth, as well as expenditures related to employee training and compliance with pipeline safety regulations. On September 28, 2016, Columbia of Virginia implemented updated interim base rates subject to refund. On January 17, 2017, Columbia of Virginia presented a stipulation and proposed recommendation, representing a settlement by all parties to the proceeding, that included a base revenue increase of $28.5 million . On February 8, 2017, the Hearing Examiner in the case filed a report recommending approval of the stipulation and proposed recommendation. A VSCC decision on the proposed recommendation is expected in the first half of 2017. Columbia of Kentucky. On May 27, 2016, Columbia of Kentucky filed a base rate case with the Kentucky PSC, seeking an annual revenue increase of $25.4 million . This case was driven by Columbia of Kentucky's ongoing initiatives to improve the overall safety and reliability of its gas distribution system. On October 20, 2016, a settlement was reached which included an annual revenue increase of $13.4 million . On December 22, 2016, the Kentucky PSC issued an order modifying the stipulation, resulting in an annual revenue increase of $13.1 million . Columbia of Kentucky accepted this modification, and rates went into effect on December 27, 2016. Columbia of Maryland. On April 15, 2016, Columbia of Maryland filed a base rate case with the MPSC, seeking an annual revenue increase of $6.5 million . The case was driven by Columbia of Maryland’s ongoing capital investment program and by operations and maintenance expenditures related to compliance with pipeline safety regulations. On July 27, 2016, the parties to the case filed a joint petition for approval of a proposed settlement that includes an annual revenue increase of $3.7 million . On September 26, 2016, the assigned public utility law judge issued a proposed order approving the settlement without modification. There were no appeals to the administrative law judge's proposed order. As such, it became the order of the MPSC, and rates went into effect on October 27, 2016. Electric Operations Regulatory Matters Cost Recovery and Trackers . Comparability of Electric Operations line item operating results is impacted by regulatory trackers that allow for the recovery in rates of certain costs such as those described below. Increases in the expenses that are the subject of trackers result in a corresponding increase in net revenues and therefore have essentially no impact on total operating income results. 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 through 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, resource capacity charges, and environmental related costs. A portion of NIPSCO's revenue is related to the recovery of fuel costs to generate power and the fuel costs related to purchased power. These costs are recovered through a FAC, a quarterly, regulatory proceeding in Indiana. 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 and (2) related operation and maintenance and depreciation expenses once the environmental facilities become operational. On October 26, 2016, the IURC issued an order on ECR-28 approving NIPSCO's request to begin earning a return on $267.0 million of cumulative net capital expenditures invested through June 30, 2016. Rates went into effect November 1, 2016. On January 31, 2017, NIPSCO filed ECR-29 which included $261.1 million of net capital expenditures for the period ended December 31, 2016. An order is expected in the second quarter of 2017. On October 1, 2015, NIPSCO filed an electric base rate case with the IURC, seeking a revenue increase of $126.6 million , before certain riders. As part of this filing, NIPSCO proposed to update base rates for previously incurred infrastructure improvements, revised depreciation rates and the inclusion of previously approved environmental and federally mandated compliance costs. On February 19, 2016, a stipulation and settlement agreement was filed with the IURC seeking a revenue increase of $72.5 million , before certain riders. On July 18, 2016, the IURC issued an order approving the settlement agreement as filed with new rates effective October 1, 2016. NIPSCO received a final order from the IURC related to its original TDSIC plan as of January 16, 2016. That order authorized NIPSCO to defer, as a regulatory asset, 100% of all TDSIC costs incurred from March 1, 2014 through December 31, 2015 until such deferral is recovered as part of its next general rate case. As discussed above, the electric general rate case was approved on July 18, 2016, which allows for recovery in base rates of 100% of these previously incurred TDSIC costs. This approval allowed NIPSCO to record a regulatory asset of approximately $7.8 million in the third quarter of 2016. On December 31, 2015, NIPSCO filed a new electric TDSIC seven-year plan of eligible investments for a total of approximately $1.3 billion covering spend in years 2016 through 2022. On March 24, 2016, a stipulation and settlement agreement was filed with the IURC which, among other things, sought approval of a seven-year plan that includes approximately $1.25 billion of investments eligible for ratemaking treatment. On July 12, 2016, the IURC issued an order approving the settlement agreement. Consistent with the terms of the aforementioned electric TDSIC settlement agreement, NIPSCO made a TDSIC rate adjustment mechanism filing on June 30, 2016 seeking recovery and ratemaking relief associated with $45.5 million of cumulative net capital expenditures invested through April 30, 2016. An IURC order approving NIPSCO's filing was received on January 25, 2017. New rates went into effect with the first billing cycle of February 2017. NIPSCO has been participating as one of the MISO transmission owners in defending two separate complaints filed at the FERC which challenge the MISO prescribed 12.38% base ROE for electric transmission investments subject to federal jurisdiction rate regulation. On June 30, 2016, the FERC administrative law judge issued an initial decision in the second complaint which authorized the MISO transmission owners to collect a base ROE of 9.7% for the period of February 12, 2015 through May 11, 2016. This initial decision is subject to approval by the full Commission and is not a final order. On September 28, 2016, FERC issued Opinion No. 551, which largely affirmed the initial decision in the first complaint, which set the base ROE for the MISO Transmission Owners at 10.32% for the period of November 12, 2013 through February 11, 2015. The FERC directed the MISO and the MISO Transmission Owners to submit, within 30 days, a compliance filing with revised rates based on the 10.32% base ROE and to provide refunds with interest for the 15-month refund period for this case. The opinion also establishes the going forward base ROE at 10.32% as of September 28, 2016 until the Commission either issues a final order in the second complaint or a new proceeding is initiated to create a new refund period. Incorporating NIPSCO’s 50-basis point adder for independent RTO membership, NIPSCO’s total ROE is set at 10.82% going forward. NIPSCO has an estimated liability of $6.5 million at December 31, 2016 related to this matter. On November 1, 2016, NIPSCO filed a petition with the IURC for relief regarding the construction of additional environmental projects required to comply with the final rules for regulation of CCRs and the ELG. Refer to Note 18-D, “Environmental Matters,” for more information.

Risk Management Activities

Risk Management Activities	12 Months Ended
	Dec. 31, 2016
Risk Management Activities [Abstract]
Risk Management Activities	Risk Management Activities NiSource is exposed to certain risks relating to its ongoing business operations; namely commodity price risk and interest rate risk. NiSource recognizes that the prudent and selective use of derivatives may help to lower its cost of debt capital, manage its interest rate exposure and limit volatility in the price of natural gas. Risk management assets and liabilities on NiSource’s derivatives are presented on the Consolidated Balance Sheets as shown below: (in millions) 2016 2015 Risk Management Assets - Current (1) Interest rate risk programs $ 17.0 $ — Commodity price risk programs 7.4 0.1 Total $ 24.4 $ 0.1 Risk Management Assets - Noncurrent (2) Interest rate risk programs $ 17.1 $ — Commodity price risk programs 7.5 — Total $ 24.6 $ — Risk Management Liabilities - Current (3) Interest rate risk programs $ 15.3 $ — Commodity price risk programs 1.5 9.3 Total $ 16.8 $ 9.3 Risk Management Liabilities - Noncurrent Interest rate risk programs $ 24.5 $ 17.4 Commodity price risk programs 20.0 5.2 Total $ 44.5 $ 22.6 (1) Presented in "Prepayments and other" on the Consolidated Balance Sheets. (2) Presented in "Deferred charges and other" on the Consolidated Balance Sheets. (3) Presented in "Other accruals" on the Consolidated Balance Sheets. Commodity Price Risk Management NiSource and NiSource’s utility customers are exposed to variability in cash flows associated with natural gas purchases and volatility in natural gas prices. NiSource purchases natural gas for sale and delivery to its retail, commercial and industrial customers, and for most customers the variability in the market price of gas is passed through in their rates. Some of NiSource’s utility subsidiaries offer programs where variability in the market price of gas is assumed by the respective utility. The objective of NiSource’s commodity price risk programs is to mitigate the gas cost variability, for NiSource or on behalf of its customers, associated with natural gas purchases or sales by economically hedging the various gas cost components using a combination of futures, options, forwards or other derivative contracts. In September 2016, NIPSCO received IURC approval to lock in a fixed price for its natural gas customers using long-term forward purchase instruments. The term of these instruments may range from five to ten years and is limited to ten percent of NIPSCO’s average annual GCA purchase volume. Gains and losses on these derivative contracts will be deferred as regulatory liabilities or assets and will be remitted to or collected from customers through NIPSCO’s quarterly GCA mechanism. These instruments are not designated as accounting hedges. Interest Rate Risk Management In 2015, NiSource Finance entered into forward-starting interest rate swap agreements with an aggregate notional value of $1.0 billion to hedge the variability in cash flows attributable to changes in the benchmark interest rate during the periods from the effective dates of the swaps to the anticipated dates of forecasted debt issuances which extend into 2018 . In June 2016, NiSource Finance entered into additional forward-starting interest rate swap agreements with an aggregate notional value of $500.0 million to hedge the variability in cash flows attributable to changes in the benchmark interest rate during the periods from the effective dates of the swaps to the anticipated dates of forecasted debt issuances, which are expected to take place by the end of 2018. As of December 31, 2016, NiSource Finance has forward-starting interest rate swaps with an aggregate notional value totaling $1.5 billion . These interest rate swaps are designated as cash flow hedges. The effective portions of the gains and losses related to these swaps are recorded to AOCI and are recognized in earnings concurrent with the recognition of interest expense on the associated debt, once issued. If it becomes probable that a hedged forecasted transaction will no longer occur, the accumulated gains or losses on the derivative will be recognized currently in earnings. Earnings may also be impacted if the anticipated dates of forecasted debt issuances differ from the dates originally contemplated at hedge inception. Realized gains and losses from NiSource’s interest rate cash flow hedges are presented in “Interest expense, net” on the Statements of Consolidated Income. There was no material income statement recognition of gains or losses relating to an ineffective portion of NiSource's hedges, nor were there amounts excluded from effectiveness testing for derivatives in cash flow hedging relationships for the years ended December 31, 2016, 2015 and 2014. NiSource’s derivative instruments measured at fair value as of December 31, 2016 and 2015 do not contain any credit-risk-related contingent features.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The components of income tax expense (benefit) were as follows: Year Ended December 31, (in millions) 2016 2015 2014 Income Taxes Current Federal $ — $ — $ — State (0.1 ) 6.0 5.4 Total Current (0.1 ) 6.0 5.4 Deferred Federal 165.6 124.1 129.5 State 18.0 13.6 35.4 Total Deferred 183.6 137.7 164.9 Deferred Investment Credits (1.4 ) (2.4 ) (3.5 ) Income Taxes from Continuing Operations $ 182.1 $ 141.3 $ 166.8 Total income taxes from continuing operations were different from the amount that would be computed by applying the statutory federal income tax rate to book income before income tax. The major reasons for this difference were as follows: Year Ended December 31, (in millions) 2016 2015 2014 Book income from Continuing Operations before income taxes $ 510.2 $ 339.9 $ 423.0 Tax expense at statutory Federal income tax rate 178.6 35.0 % 118.9 35.0 % 148.1 35.0 % Increases (reductions) in taxes resulting from: State income taxes, net of Federal income tax benefit 11.3 2.2 14.8 4.4 15.7 3.7 Regulatory treatment of depreciation differences 2.1 0.4 4.3 1.3 0.7 0.2 Amortization of deferred investment tax credits (1.4 ) (0.3 ) (2.4 ) (0.7 ) (3.5 ) (0.8 ) Nondeductible expenses 1.9 0.4 2.1 0.6 0.8 0.2 Employee stock ownership plan dividends (2.3 ) (0.5 ) (2.9 ) (0.9 ) (3.8 ) (0.9 ) AFUDC equity (2.2 ) (0.4 ) (3.5 ) (1.0 ) (3.5 ) (0.8 ) Charitable contribution carryforward adjustment 2.8 0.5 17.8 5.2 — — Federal tax benefits on stock compensation (7.2 ) (1.4 ) — — — — Tax accrual adjustments and other, net (1.5 ) (0.2 ) (7.8 ) (2.3 ) 12.3 2.8 Income Taxes from Continuing Operations $ 182.1 35.7 % $ 141.3 41.6 % $ 166.8 39.4 % The effective income tax rates were 35.7% , 41.6% and 39.4% in 2016 , 2015 and 2014 , respectively. The 5.9% decrease in the overall effective tax rate in 2016 versus 2015 was primarily the result of a $7.2 million decrease in income taxes related to Federal tax benefits on stock compensation and the absence of $15.0 million of lost Federal tax benefit primarily related to charitable contribution carryforward adjustments recorded in the prior year. Both of these items are discussed in further detail below. The 2.2% increase in the overall effective tax rate in 2015 versus 2014 was primarily a result of a $17.8 million increase in federal income tax associated with write downs of charitable contribution carryforwards, offset by a $10.5 million decrease in income tax expense related to state apportionment changes and permanent items as a result of remeasurement after the Separation. In March 2016, the FASB issued ASU 2016-09, Compensation-Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting. Among other provisions, the standard requires that all income tax effects of awards are recognized in the income statement when the awards vest and are distributed. NiSource elected to adopt ASU 2016-09 during the third quarter of 2016. Refer to Note 2, “Recent Accounting Pronouncements,” for additional information. On December 18, 2015, the President signed into law the PATH. PATH, among other provisions, extended and modified bonus depreciation through 2019. In general, 50% bonus depreciation is available for property placed in service before January 1, 2018, 40% bonus depreciation is available for property placed in service before January 1, 2019 and 30% bonus depreciation is available for property placed in service before January 1, 2020. NiSource recorded the effects of PATH in the fourth quarter of 2015. As a result of PATH and 50% bonus depreciation being extended, NiSource recorded tax expense of $5.8 million in 2015 for the expiration of unused charitable contribution carryforwards which expired due to the 5 year carryover limitation. NiSource also recorded a valuation allowance for an additional $12.0 million of charitable contribution carryforwards that are set to expire in 2016-2019 in the event that NiSource does not have sufficient taxable income to utilize the carryforward amounts. As a result of a Pennsylvania PUC Order dated December 3, 2015, Columbia of Pennsylvania adjusted the flow through in rates of tax benefits so that the unamortized balance of a change in accounting method for certain capitalized costs of approximately $2.0 million at December 31, 2014 would be amortized through December 2016. The amortization of excess tax benefits was $0.7 million in 2016, $1.4 million in 2015 and $4.1 million in 2014 . On a prospective basis, Columbia of Pennsylvania will recognize deferred tax expense, rather than flow through in rates, the tax benefits resulting from the method change. On March 25, 2014, the governor of Indiana signed into law Senate Bill I, 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, 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. Deferred income taxes result from temporary differences between the financial statement carrying amounts and the tax basis of existing assets and liabilities. The principal components of NiSource’s net deferred tax liability were as follows: At December 31, (in millions) 2016 2015 Deferred tax liabilities Accelerated depreciation and other property-related differences $ 3,825.7 $ 3,510.8 Unrecovered gas and fuel costs 25.9 11.2 Other regulatory assets 449.2 403.3 Premiums and discounts associated with long-term debt 1.5 9.9 Total Deferred Tax Liabilities 4,302.3 3,935.2 Deferred tax assets Other regulatory liabilities (93.1 ) (74.4 ) Cost of removal (502.2 ) (519.4 ) Pension and other postretirement/postemployment benefits (261.7 ) (243.8 ) Environmental liabilities (47.0 ) (45.9 ) Net operating loss carryforward and Alternative Minimum Tax credit carryforward (646.2 ) (437.4 ) Other accrued liabilities (45.5 ) (89.0 ) Other, net (178.6 ) (160.0 ) Total Deferred Tax Assets (1,774.3 ) (1,569.9 ) Net Deferred Tax Liabilities $ 2,528.0 $ 2,365.3 State income tax net operating loss benefits are recorded at their realizable value. NiSource anticipates it is more likely than not that it will realize $43.6 million and $34.7 million of these tax benefits as of December 31, 2016 and 2015 , respectively, prior to their expiration. These tax benefits are primarily related to Indiana and Pennsylvania. The carryforward periods for these tax benefits expire in various tax years from 2028 to 2036 . The remaining net operating loss carryforward tax benefit represents a Federal carryforward of $600.9 million that will expire in 2030 and an Alternative Minimum Tax credit of $1.7 million that will carry forward indefinitely. A reconciliation of the beginning and ending amounts of unrecognized tax benefits is as follows: Reconciliation of Unrecognized Tax Benefits (in millions) 2016 2015 2014 Unrecognized Tax Benefits - Opening Balance $ 0.9 $ 24.4 $ 23.7 Gross increases - tax positions in prior period 2.6 0.4 — Gross decreases - tax positions in prior period (0.9 ) (23.9 ) (1.0 ) Gross increases - current period tax positions — — 1.7 Unrecognized Tax Benefits - Ending Balance $ 2.6 $ 0.9 $ 24.4 Offset for net operating loss carryforwards — (0.9 ) (24.2 ) Balance - Less Net Operating Loss Carryforwards $ 2.6 $ — $ 0.2 In 2016, NiSource resolved prior unrecognized tax benefits of $0.9 million and established new unrecognized tax benefits related to State matters of $2.6 million . The IRS issued Revenue Procedure 2013-24 on April 30, 2013, which provided guidance for repairs related to generation property. Among other things, the Revenue Procedure listed units of property and material components of units of property for purposes of analyzing repair versus capitalization issues. NiSource adopted this Revenue Procedure for income tax filings for 2014. NiSource evaluated and recorded the effect of this change in method enabled by this Revenue Procedure as of December 31, 2013. As a result of the findings received in 2015 for the 2011-2014 audit, NiSource reversed its previously recorded unrecognized tax benefits related to the requested change in tax accounting method in 2015. The reversal of the unrecognized tax benefits did not materially affect tax expense or net income. In 2015, offsetting the liability for unrecognized tax benefits are $0.9 million of related outstanding tax receivables and net operating loss carryforwards resulting in a net balance of zero , including interest, related to the tax method change issues. The total amount of unrecognized tax benefits at December 31, 2016 , 2015 and 2014 that, if recognized, would affect the effective tax rate is $1.7 million , $0.9 million and $4.1 million , respectively. As of December 31, 2016 , it is reasonably possible that a $1.7 million decrease in unrecorded tax benefits could occur in 2017 due primarily to the conclusion of state appeals. NiSource recognizes accrued interest on unrecognized tax benefits, accrued interest on other income tax liabilities and tax penalties in income tax expense. Interest expense recorded on unrecognized tax benefits and other income tax liabilities was immaterial for all periods presented. There were no accruals for penalties recorded in the Statements of Consolidated Income for the years ended December 31, 2016 , 2015 and 2014 , and there were no balances for accrued penalties recorded on the Consolidated Balance Sheets as of December 31, 2016 and 2015 . NiSource is subject to income taxation in the United States and various state jurisdictions, primarily Indiana, Pennsylvania, Kentucky, Massachusetts, Maryland, New York and Virginia. Because NiSource is part of the IRS’s Large and Mid-Size Business program, each year’s federal income tax return is typically audited by the IRS. As of December 31, 2016 , tax years through 2015 have been audited and are effectively closed to further assessment. The audit of tax year 2016 under the CAP program is expected to be completed in 2017. NiSource has been accepted into the program for the audit of tax year 2017. The statute of limitations in each of the state jurisdictions in which NiSource operates remain open until the years are settled for federal income tax purposes, at which time amended state income tax returns reflecting all federal income tax adjustments are filed. As of December 31, 2016 , there were no state income tax audits in progress that would have a material impact on the consolidated financial statements.

Pension And Other Postretiremen

Pension And Other Postretirement Benefits	12 Months Ended
	Dec. 31, 2016
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 certain of 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. In connection with the Separation, NiSource entered into an Employees Matters Agreement with CPG, which provides that employees of CPG no longer participate in benefit plans sponsored by NiSource as of the Separation date. Upon the completion of the Separation, the NiSource pension and other postretirement benefit plans transferred assets and obligations to the CPG plans resulting in a net decrease in the pension plans underfunded status of $48.0 million and a net increase in the other postretirement benefit plans underfunded status of $115.9 million . Refer to Note 3, "Discontinued Operations," for additional information. NiSource Pension and Other Postretirement Benefit Plans’ Asset Management . NiSource employs a liability-driven investing strategy for the pension plan, as noted below. While the majority of assets continue in a total return investment approach, a glide path has been implemented. A mix of equities and fixed income investments are used to maximize the long-term return of plan assets and hedge the liabilities at a prudent level of risk. NiSource utilizes a total return investment approach for the other postretirement benefit plans. Risk tolerance is established through careful consideration of plan liabilities, plan funded status, and asset class volatility. The investment portfolio contains a diversified blend of equity and fixed income investments. Furthermore, equity investments are diversified across U.S. and non-U.S. stocks, as well as growth, value, small and large capitalizations. Other assets such as private equity funds are used judiciously to enhance long-term returns while improving portfolio diversification. Derivatives may be used to gain market exposure in an efficient and timely manner; however, derivatives may not be used to leverage the portfolio beyond the market value of the underlying assets. Investment risk is measured and monitored on an ongoing basis through quarterly investment portfolio reviews, annual liability measurements, and periodic asset/liability studies. NiSource utilizes a building block approach with proper consideration of diversification and rebalancing in determining the long-term rate of return for plan assets. Historical markets are studied and long-term historical relationships between equities and fixed income are analyzed to ensure that they are consistent with the widely accepted capital market principle that assets with higher volatility generate greater return over the long run. Current market factors, such as inflation and interest rates, are evaluated before long-term capital market assumptions are determined. Peer data and historical returns are reviewed to check for reasonability and appropriateness. The most important component of an investment strategy is the portfolio asset mix, or the allocation between the various classes of securities available to the pension and other postretirement benefit plans for investment purposes. The asset mix and acceptable minimum and maximum ranges established for the NiSource plan assets represents a long-term view and are listed in the table below. In 2012, a dynamic asset allocation policy for the pension fund was approved. This policy calls for a gradual reduction in the allocation of return-seeking assets (equities, real estate, private equity and hedge funds) and a corresponding increase in the allocation of liability-hedging assets (fixed income) as the funded status of the plans increase above 90% (as measured by the market value of qualified pension plan assets divided by the projected benefit obligations of the qualified pension plans). In 2016, a study was conducted and approved resulting in the addition of new asset classes in the return-seeking portfolio allocation (i.e. core real estate, diversified credit) and a shift in the hedging allocation (i.e. fixed income). Planned implementation of the new asset classes will begin in 2017. As of December 31, 2016, the asset mix and acceptable minimum and maximum ranges established by the policy for the pension and other postretirement benefit plans are as follows: Asset Mix Policy of Funds: Defined Benefit Pension Plan Postretirement Benefit Plan Asset Category Minimum Maximum Minimum Maximum Domestic Equities 25% 45% 35% 55% International Equities 15% 25% 15% 25% Fixed Income 23% 37% 20% 50% Real Estate/Private Equity/Hedge Funds 0% 15% 0% 0% Short-Term Investments 0% 10% 0% 10% Pension Plan and Postretirement Plan Asset Mix at December 31, 2016 and December 31, 2015 : (in millions) Defined Benefit Pension Assets December 31, Postretirement December 31, Asset Class Asset Value % of Total Assets Asset Value % of Total Assets Domestic Equities $ 755.2 43.1 % $ 97.9 42.3 % International Equities 339.9 19.4 % 41.8 18.0 % Fixed Income 565.8 32.3 % 87.0 37.6 % Real Estate/Private Equity/Hedge Funds 74.8 4.3 % — — Cash/Other 15.2 0.9 % 4.7 2.1 % Total $ 1,750.9 100.0 % $ 231.4 100.0 % (in millions) Defined Benefit Pension Assets December 31, Postretirement Benefit Plan Assets December 31, Asset Class Asset Value % of Total Assets Asset Value % of Total Assets Domestic Equities $ 686.3 39.3 % $ 105.0 46.5 % International Equities 323.2 18.5 % 39.6 17.5 % Fixed Income 619.3 35.5 % 79.1 35.0 % Real Estate/Private Equity/Hedge Funds 96.7 5.5 % — — Cash/Other 21.6 1.2 % 2.2 1.0 % Total $ 1,747.1 100.0 % $ 225.9 100.0 % The categorization of investments into the asset classes in the table above are based on definitions established by the NiSource Benefits Committee. Fair Value Measurements. The following table sets forth, by level within the fair value hierarchy, the Master Trust and other postretirement benefits investment assets at fair value as of December 31, 2016 and 2015 . Assets and liabilities are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. Total Master Trust and other postretirement benefits investment assets at fair value classified within Level 3 were $73.1 million and $95.3 million as of December 31, 2016 and December 31, 2015 , respectively. Such amounts were approximately 4% and 5% of the Master Trust and other postretirement benefits’ total investments as reported on the statement of net assets available for benefits at fair value as of December 31, 2016 and 2015 , respectively. Valuation Techniques Used to Determine Fair Value: Level 1 Measurements Most common and preferred stocks are traded in active markets on national and international securities exchanges and are valued at closing prices on the last business day of each period presented. Cash is stated at cost which approximates fair value, with the exception of cash held in foreign currencies which fluctuates with changes in the exchange rates. Short-term bills and notes are priced based on quoted market values. Level 2 Measurements Most U.S. Government Agency obligations, mortgage/asset-backed securities, and corporate fixed income securities are generally valued by benchmarking model-derived prices to quoted market prices and trade data for identical or comparable securities. To the extent that quoted prices are not available, fair value is determined based on a valuation model that includes inputs such as interest rate yield curves and credit spreads. Securities traded in markets that are not considered active are valued based on quoted market prices, broker or dealer quotations, or alternative pricing sources with reasonable levels of price transparency. Other fixed income includes futures and options which are priced on bid valuation or settlement pricing. Commingled funds that hold underlying investments that have prices which are derived from the quoted prices in active markets are classified as Level 2. The funds' underlying assets are principally marketable equity and fixed income securities. Units held in commingled funds are valued at the unit value as reported by the investment managers. The fair value of the investments in commingled funds has been estimated using the net asset value per share of the investments. Level 3 Measurements Commingled funds that hold underlying investments that have prices which are not derived from the quoted prices in active markets are classified as Level 3. The respective fair values of these investments are determined by reference to the funds' underlying assets, which are principally marketable equity and fixed income securities. Units held in commingled funds are valued at the unit value as reported by the investment managers. These investments are often valued by investment managers on a periodic basis using pricing models that use market, income and cost valuation methods. Private equity investment strategies include buy-out, venture capital, growth equity, distressed debt, and mezzanine debt. Private equity investments are held through limited partnerships. Limited partnerships are valued at estimated fair market value based on their proportionate share of the partnership's fair value as recorded in the partnerships' audited financial statements. Partnership interests represent ownership interests in private equity funds and real estate funds. Real estate partnerships invest in natural resources, commercial real estate and distressed real estate. The fair value of these investments is determined by reference to the funds' underlying assets, which are principally securities, private businesses, and real estate properties. The value of interests held in limited partnerships, other than securities, is determined by the general partner, based upon third-party appraisals of the underlying assets, which include inputs such as cost, operating results, discounted cash flows and market based comparable data. Private equity and real estate limited partnerships typically call capital over a three to five year period and pay out distributions as the underlying investments are liquidated. The typical expected life of these limited partnerships is 10-15 years and these investments typically cannot be redeemed prior to liquidation. For the year ended December 31, 2016 , there were no significant changes to valuation techniques to determine the fair value of NiSource's pension and other postretirement benefits' assets. Fair Value Measurements at December 31, 2016 : (in millions) December 31, Quoted Prices in Active Significant Other Significant Pension plan assets: Cash $ 1.9 $ 1.9 $ — $ — Fixed income securities Government 42.2 — 42.2 — Corporate 104.1 — 104.1 — Other fixed income 0.1 — — 0.1 Mutual Funds U.S. multi-strategy 283.2 283.2 — — International equities 116.6 116.6 — — Fixed income 135.6 135.6 — — Private equity limited partnerships U.S. multi-strategy (1) 34.8 — — 34.8 International multi-strategy (2) 24.9 — — 24.9 Distressed opportunities 4.1 — — 4.1 Real estate 9.2 — — 9.2 Commingled funds Short-term money markets (3) 16.6 U.S. equities (3) 472.0 International equities (3) 223.2 Fixed income (3) 280.7 Pension plan assets subtotal 1,749.2 537.3 146.3 73.1 Other postretirement benefit plan assets: Mutual funds U.S. equities 85.4 85.4 — — International equities 41.8 41.8 — — Fixed income 86.8 86.8 — — Commingled funds Short-term money markets (3) 9.5 U.S. equities (3) 12.5 Other postretirement benefit plan assets subtotal 236.0 214.0 — — Due to brokers, net (4) (5.0 ) Receivables/payables 2.1 Total pension and other postretirement benefit plan assets $ 1,982.3 $ 751.3 $ 146.3 $ 73.1 (1) This class includes limited partnerships/fund of funds that invest in a diverse portfolio of private equity strategies, including buy-outs, venture capital, growth capital, special situations and secondary markets, primarily inside the United States. (2) This class includes limited partnerships/fund of funds that invest in diverse portfolio of private equity strategies, including buy-outs, venture capital, growth capital, special situations and secondary markets, primarily outside the United States. (3) This class of investments is measured at fair value using the net asset value per share and has not been classified in the fair value hierarchy. (4) This class represents pending trades with brokers. The table below sets forth a summary of changes in the fair value of the Plan’s Level 3 assets for the year ended December 31, 2016 : Balance at January 1, 2016 Total gains or losses (unrealized / realized) Purchases (Sales) Transfers into/(out of) level 3 Balance at December 31, 2016 Fixed income securities Other fixed income $ 0.1 $ — $ — $ — $ — $ 0.1 Private equity limited partnerships U.S. multi-strategy 46.4 2.1 0.8 (14.5 ) — 34.8 International multi-strategy 29.3 2.0 1.0 (7.4 ) — 24.9 Distressed opportunities 5.9 (0.4 ) 0.1 (1.5 ) — 4.1 Real estate 13.6 0.1 0.1 (4.6 ) — 9.2 Total $ 95.3 $ 3.8 $ 2.0 $ (28.0 ) $ — $ 73.1 The table below sets forth a summary of unfunded commitments, redemption frequency and redemption notice periods for certain investments that are measured at fair value using the net asset value per share for the year ended December 31, 2016 : (in millions) Fair Value Unfunded Commitments Redemption Frequency Redemption Notice Period Commingled Funds Short-term money markets $ 26.1 $ — Daily 1 day U.S. equities 484.5 — Monthly 3 days International equities 223.2 — Monthly 14-30 days Fixed income 280.7 — Monthly 3 days Total $ 1,014.5 $ — Fair Value Measurements at December 31, 2015 : (in millions) December 31, Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Significant Pension plan assets: Cash $ 7.0 $ 7.0 $ — $ — Equity securities International equities 45.3 45.3 — — Fixed income securities Government 64.6 — 64.6 — Corporate 95.8 — 95.8 — Other fixed income 0.1 — — 0.1 Mutual Funds U.S. multi-strategy 257.1 257.1 — — International equities 64.9 64.9 — — Fixed income 150.5 150.5 — — Private equity limited partnerships U.S. multi-strategy (1) 46.4 — — 46.4 International multi-strategy (2) 29.3 — — 29.3 Distressed opportunities 5.9 — — 5.9 Real Estate 13.6 — — 13.6 Commingled funds Short-term money markets (3) 22.9 U.S. equities (3) 429.2 International equities (3) 210.1 Fixed income (3) 302.5 Pension plan assets subtotal 1,745.2 524.8 160.4 95.3 Other postretirement benefit plan assets: Mutual funds U.S. equities 89.8 89.8 — — International equities 41.4 41.4 — — Fixed income 78.0 78.0 — — Commingled funds Short-term money markets (3) 2.4 U.S. equities (3) 14.3 Other postretirement benefit plan assets subtotal 225.9 209.2 — — Due to brokers, net (4) (0.2 ) Receivables/payables 2.1 Total pension and other postretirement benefit plan assets $ 1,973.0 $ 734.0 $ 160.4 $ 95.3 (1) This class includes limited partnerships/fund of funds that invest in a diverse portfolio of private equity strategies, including buy-outs, venture capital, growth capital, special situations and secondary markets, primarily in the United States. (2) This class includes limited partnerships/fund of funds that invest in a diverse portfolio of private equity strategies, including buy-outs, venture capital, growth capital, special situations and secondary markets, primarily outside the United States. (3) This class of investments is measured at fair value using the net asset value per share and has not been classified in the fair value hierarchy. (4) This class represents pending trades with brokers. The table below sets forth a summary of changes in the fair value of the Plan’s Level 3 assets for the year ended December 31, 2015 : Balance at January 1, 2015 Total gains or losses (unrealized / realized) Purchases (Sales) Transfers into/(out of) level 3 Balance at December 31, 2015 Fixed income securities Other fixed income $ 0.6 $ — $ — $ (0.5 ) $ — $ 0.1 Private equity limited partnerships U.S. multi-strategy 56.2 (3.5 ) 1.1 (7.4 ) — 46.4 International multi-strategy 35.3 (2.3 ) 0.1 (3.8 ) — 29.3 Distress opportunities 7.6 (0.5 ) — (1.2 ) — 5.9 Real estate 17.3 (0.5 ) 0.1 (3.3 ) — 13.6 Total $ 117.0 $ (6.8 ) $ 1.3 $ (16.2 ) $ — $ 95.3 The table below sets forth a summary of unfunded commitments, redemption frequency and redemption notice periods for certain investments that are measured at fair value using the net asset value per share for the year ended December 31, 2015 : (in millions) Fair Value Unfunded Commitments Redemption Frequency Redemption Notice Period Commingled Funds Short-term money markets $ 25.3 $ — Daily 1 day U.S. equities 443.5 — Monthly 3 days International equities 210.1 — Monthly 14-30 days Fixed income 302.5 — Monthly 3 days Total $ 981.4 $ — NiSource Pension and Other Postretirement Benefit Plans’ Funded Status and Related Disclosure . The following table provides a reconciliation of the plans’ funded status and amounts reflected in NiSource’s Consolidated Balance Sheets at December 31 based on a December 31 measurement date: Pension Benefits Other Postretirement Benefits (in millions) 2016 2015 2016 2015 Change in projected benefit obligation (1) Benefit obligation at beginning of year $ 2,206.7 $ 2,751.4 $ 525.8 $ 716.0 Service cost 30.7 34.8 5.0 6.4 Interest cost 89.7 95.9 22.0 24.9 Plan participants’ contributions — — 5.9 7.3 Plan amendments — — 7.5 0.1 Actuarial loss (gain) (2.7 ) (91.7 ) 1.0 (71.5 ) Settlement loss — 0.5 — — Benefits paid (158.6 ) (171.8 ) (38.9 ) (43.7 ) Estimated benefits paid by incurred subsidy — — 0.7 0.8 Separation of CPG (Note 3) — (412.4 ) — (114.5 ) Projected benefit obligation at end of year $ 2,165.8 $ 2,206.7 $ 529.0 $ 525.8 Change in plan assets Fair value of plan assets at beginning of year $ 1,747.1 $ 2,330.3 $ 225.9 $ 465.0 Actual return on plan assets 159.1 (49.7 ) 13.0 1.9 Employer contributions 3.3 2.7 25.5 25.8 Plan participants’ contributions — — 5.9 7.3 Benefits paid (158.6 ) (171.8 ) (38.9 ) (43.7 ) Separation of CPG (Note 3) — (364.4 ) — (230.4 ) Fair value of plan assets at end of year $ 1,750.9 $ 1,747.1 $ 231.4 $ 225.9 Funded Status at end of year $ (414.9 ) $ (459.6 ) $ (297.6 ) $ (299.9 ) Amounts recognized in the statement of financial position consist of: Current liabilities (2.9 ) (3.0 ) (0.7 ) (0.6 ) Noncurrent liabilities (412.0 ) (456.6 ) (296.9 ) (299.3 ) Net amount recognized at end of year (2) $ (414.9 ) $ (459.6 ) $ (297.6 ) $ (299.9 ) Amounts recognized in accumulated other comprehensive income or regulatory asset/liability (3) Unrecognized prior service credit $ 1.0 $ 0.7 $ (29.2 ) $ (41.6 ) Unrecognized actuarial loss 835.5 925.6 68.3 66.1 Net amount recognized at end of year $ 836.5 $ 926.3 $ 39.1 $ 24.5 (1) The change in benefit obligation for Pension Benefits represents the change in Projected Benefit Obligation while the change in benefit obligation for Other Postretirement Benefits represents the change in Accumulated Postretirement Benefit Obligation. (2) NiSource recognizes in its Consolidated Balance Sheets the underfunded and overfunded status of its various defined benefit postretirement plans, measured as the difference between the fair value of the plan assets and the benefit obligation. (3) NiSource determined that for certain rate-regulated subsidiaries the future recovery of pension and other postretirement benefits costs is probable. These rate-regulated subsidiaries recorded regulatory assets and liabilities of $847.5 million and $0.3 million , respectively, as of December 31, 2016 , and $928.7 million and $8.1 million , respectively, as of December 31, 2015 that would otherwise have been recorded to accumulated other comprehensive loss. NiSource’s accumulated benefit obligation for its pension plans was $2,148.9 million and $2,190.5 million as of December 31, 2016 and 2015 , respectively. The accumulated benefit obligation as of a date is the actuarial present value of benefits attributed by the pension benefit formula to employee service rendered prior to that date and based on current and past compensation levels. The accumulated benefit obligation differs from the projected benefit obligation disclosed in the table above in that it includes no assumptions about future compensation levels. NiSource pension plans were underfunded by $414.9 million at December 31, 2016 compared to being underfunded at December 31, 2015 by $459.6 million . The improvement in the funded status was due primarily to favorable asset returns offset by a decrease in discount rates. NiSource contributed $3.3 million and $2.7 million to its pension plans in 2016 and 2015 , respectively. NiSource’s other postretirement benefit plans were underfunded by $297.6 million at December 31, 2016 compared to being underfunded at December 31, 2015 by $299.9 million . The improvement in funded status was primarily due to favorable asset returns offset by a decrease in discount rates. NiSource contributed approximately $25.5 million and $25.8 million to its other postretirement benefit plans in 2016 and 2015 , respectively. No amounts of NiSource’s pension or other postretirement benefit plans’ assets are expected to be returned to NiSource or any of its subsidiaries in 2016. The following table provides the key assumptions that were used to calculate the pension and other postretirement benefits obligations for NiSource’s various plans as of December 31: Pension Benefits Other Postretirement Benefits 2016 2015 2016 2015 Weighted-average assumptions to Determine Benefit Obligation Discount Rate 4.03 % 4.24 % 4.12 % 4.33 % Rate of Compensation Increases 4.00 % 4.00 % — — Health Care Trend Rates Trend for Next Year — — 8.43 % 8.41 % Ultimate Trend — — 4.50 % 4.50 % Year Ultimate Trend Reached — — 2024 2022 Assumed health care cost trend rates have a significant effect on the amounts reported for the health care plans. A one-percentage-point change in assumed health care cost trend rates would have the following effects: (in millions) 1% point increase 1% point decrease Effect on service and interest components of net periodic cost $ 1.3 $ (1.1 ) Effect on accumulated postretirement benefit obligation 27.2 (23.8 ) NiSource expects to make contributions of approximately $9.1 million to its pension plans and approximately $25.3 million to its postretirement medical and life plans in 2017 . The following table provides benefits expected to be paid in each of the next five fiscal years, and in the aggregate for the five fiscal years thereafter. The expected benefits are estimated based on the same assumptions used to measure NiSource’s benefit obligation at the end of the year and includes benefits attributable to the estimated future service of employees: (in millions) Pension Benefits Other Federal Year(s) 2017 $ 171.9 $ 34.1 $ 0.7 2018 172.5 34.9 0.7 2019 171.1 35.8 0.7 2020 171.2 36.5 0.7 2021 172.2 37.2 0.7 2022-2026 816.8 180.9 2.9 The following table provides the components of the plans’ net periodic benefits cost for each of the three years ended December 31, 2016 , 2015 and 2014 : Pension Benefits Other Postretirement Benefits (in millions) 2016 2015 2014 2016 2015 2014 Components of Net Periodic Benefit Cost (Income) Service cost $ 30.7 $ 34.8 $ 34.8 $ 5.0 $ 6.4 $ 8.5 Interest cost 89.7 95.9 109.0 22.0 24.9 30.1 Expected return on assets (132.9 ) (167.2 ) (181.1 ) (17.2 ) (28.2 ) (36.8 ) Amortization of prior service cost (credit) (0.2 ) 0.1 0.2 (4.9 ) (5.2 ) (4.3 ) Recognized actuarial loss 61.2 59.3 47.5 3.1 3.4 0.4 Net Periodic Benefit Costs (Income) 48.5 22.9 10.4 8.0 1.3 (2.1 ) Additional loss recognized due to: Settlement loss — 2.5 — — — — Total Net Periodic Benefits Cost (Income) $ 48.5 $ 25.4 $ 10.4 $ 8.0 $ 1.3 $ (2.1 ) The following table provides the key assumptions that were used to calculate the net periodic benefits cost for NiSource’s various plans: Pension Benefits Other Postretirement Benefits 2016 2015 2014 2016 2015 2014 Weighted-average Assumptions to Determine Net Periodic Benefit Cost Discount Rate 4.24 % 3.81 % 4.50 % 4.33 % 3.94 % 4.75 % Expected Long-Term Rate of Return on Plan Assets 8.00 % 8.30 % 8.30 % 7.85 % 8.15 % 8.14 % Rate of Compensation Increases 4.00 % 4.00 % 4.00 % — — — NiSource believes it is appropriate to assume an 8.00% and 7.85% rate of return on pension and other postretirement plan assets, respectively, for its calculation of 2016 pension benefits cost. These rates are primarily based on asset mix and historical rates of return and were adjusted in the current year due to anticipated changes in asset allocation and projected market returns. Beginning January 1, 2017, NiSource will change the method used to estimate the service and interest components of net periodic benefit cost for pension and other postretirement benefits. This change, compared to the previous method, is expected to result in a decrease in the actuarially-determined service and interest cost components. Historically, NiSource estimated service and interest costs utilizing a single weighted-average discount rate derived from the yield curve used to measure the benefit obligation at the beginning of the period. For fiscal 2017 and beyond, NiSource elected to utilize a full yield curve approach to estimate these components by applying the specific spot rates along the yield curve used in the determination of the benefit obligation to the relevant projected cash flows. NiSource believes the new approach provides a more precise measurement of service and interest costs by aligning the timing of the plan’s liability cash flows to the corresponding spot rates on the yield curve. The benefit obligations measured under this approach are unchanged. NiSource will account for this change as a change in accounting estimate and accordingly will account for this prospectively. The following table provides other changes in plan assets and projected benefit obligations recognized in other comprehensive income or regulatory asset or liability: Pension Benefits Other Postretirement Benefits (in millions) 2016 2015 2016 2015 Other Changes in Plan Assets and Projected Benefit Obligations Recognized in Other Comprehensive Income or Regulatory Asset or Liability Net prior service cost $ — $ — $ 7.5 $ 0.1 Net actuarial loss (gain) (28.9 ) 125.7 5.3 (45.2 ) Settlements — (2.5 ) — — Less: amortization of prior service cost (credit) 0.2 (0.1 ) 4.9 5.2 Less: amortization of net actuarial gain (61.2 ) (59.3 ) (3.1 ) (3.4 ) Less: Separation of CPG (Note 3) — (143.8 ) — 21.5 Total Recognized in Other Comprehensive Income or Regulatory Asset or Liability $ (89.9 ) $ (80.0 ) $ 14.6 $ (21.8 ) Amount Recognized in Net Periodic Benefits Cost and Other Comprehensive Income or Regulatory Asset or Liability $ (41.4 ) $ (54.6 ) $ 22.6 $ (20.5 ) Based on a December 31 measurement date, the net unrecognized actuarial loss, unrecognized prior service cost (credit), and unrecognized transition obligation that will be amortized into net periodic benefit cost during 2017 for the pension plans are $53.6 million , $(0.7) million and zero , respectively, and for other postretirement benefit plans are $3.0 million , $(4.4) million and zero , respectively.

Common Stock

Common Stock	12 Months Ended
	Dec. 31, 2016
Common Stock, Number of Shares, Par Value and Other Disclosures [Abstract]
Common Stock	Common Stock As of December 31, 2016 , NiSource had 400,000,000 authorized shares of common stock with a $0.01 par value. Common Stock Dividend. Holders of shares of NiSource’s common stock are entitled to receive dividends when, as and if declared by the Board out of funds legally available. The policy of the Board has been to declare cash dividends on a quarterly basis payable on or about the 20th day of February, May, August and November. NiSource has paid quarterly common dividends totaling $0.64 , $0.83 and $1.02 per share for the years ended December 31, 2016 , 2015 and 2014 , respectively. At its January 27, 2017 meeting, the Board declared a quarterly common dividend of $0.175 per share, payable on February 17, 2017 to holders of record on February 10, 2017 . NiSource has certain debt covenants which could potentially limit the amount of dividends the Company could pay in order to maintain compliance with these covenants. Refer to Note 14, "Long-Term Debt," for more information. As of December 31, 2016 , these covenants did not restrict the amount of dividends that were available to be paid. Dividend Reinvestment and Stock Purchase Plan. NiSource offers a Dividend Reinvestment and Stock Purchase Plan which allows participants to reinvest dividends and make voluntary cash payments to purchase additional shares of common stock on the open market.

Share-Based Compensation

Share-Based Compensation	12 Months Ended
	Dec. 31, 2016
Share-based Compensation [Abstract]
Share-Based Compensation	Share-Based Compensation The NiSource stockholders originally approved and adopted the NiSource Inc. 2010 Omnibus Incentive Plan (“Omnibus Plan”) at the Annual Meeting of Stockholders held on May 11, 2010. Stockholders re-approved the Omnibus Plan as amended at the Annual Meeting of Stockholders held on May 12, 2015. The Omnibus Plan provides for awards to employees and non-employee directors of incentive and nonqualified stock options, stock appreciation rights, restricted stock, restricted stock units, performance shares, performance units, cash-based awards and other stock-based awards and supersedes the long-term incentive plan approved by stockholders on April 13, 1994 (“1994 Plan”) and the Director Stock Incentive Plan (“Director Plan”). 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 that expire or terminate for any reason that were granted under either the 1994 Plan or the Director Plan, plus the number of shares that were awarded as a result of the Separation-related adjustments. At December 31, 2016 , there were 4,992,782 shares reserved for future awards under the Omnibus Plan. NiSource recognized stock-based employee compensation expense of $15.1 million , $18.8 million and $29.8 million , during 2016 , 2015 and 2014 , respectively, as well as related tax benefits of $5.8 million , $7.2 million and $11.8 million , respectively. Additionally, NiSource adopted ASU 2016-09 in the third quarter of 2016 and recognized excess tax benefits from the distribution of vested share-based employee compensation in 2016. For the twelve months ended December 31, 2016 , $7.2 million of such benefits were recorded. Refer to Note 2, "Recent Accounting Pronouncements," and Note 10, "Income Taxes," for additional information. As of December 31, 2016 , the total remaining unrecognized compensation cost related to non-vested awards amounted to $16.3 million , which will be amortized over the weighted-average remaining requisite service period of 1.7 years. Separation-related Adjustments . In connection with the Separation, NiSource and CPG entered into an Employee Matters Agreement, effective July 1, 2015. Under the terms of the Employee Matters Agreement, and pursuant to the terms of the Omnibus Plan, the Compensation Committee of the Board of NiSource approved an adjustment to outstanding awards granted under the Omnibus Plan in order to preserve the intrinsic aggregate value of such awards before the Separation (the “Valuation Adjustment”). The Separation-related adjustments did not have a material impact on either compensation expense or the potentially dilutive securities to be considered in the calculation of diluted earnings per share of common stock. Former NiSource employees transferred to CPG as a result of the Separation surrendered their outstanding unvested NiSource awards effective July 1, 2015. Restricted Stock Units and Restricted Stock . In 2016 , NiSource granted 65,418 restricted stock units and shares of restricted stock, subject to service conditions. The total grant date fair value of the shares of restricted stock units and shares of restricted stock was $1.4 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 over the vesting period which is generally three years. As of December 31, 2016 , all 65,418 non-vested restricted stock units and shares of restricted stock granted in 2016 were outstanding. In 2015 , NiSource granted 660,230 restricted stock units and shares of restricted stock, subject to service conditions. The total grant date fair value of the restricted stock units and shares of restricted stock was $23.9 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 over the vesting period which is generally three years. Including the effect of the Valuation Adjustment, 750,708 non-vested restricted stock units and shares of restricted stock granted in 2015 were outstanding as of December 31, 2016 . In 2014 , NiSource granted 158,633 restricted stock units and shares of restricted stock, subject to service conditions. The total grant date fair value of the restricted stock units and shares of restricted stock was $5.2 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 over the vesting period which is generally three years. Including the effect of the Valuation Adjustment, 46,810 non-vested restricted stock units and shares of restricted stock granted in 2014 were outstanding as of December 31, 2016 . As a result of the Separation, restricted stock units were substituted for outstanding performance shares awarded in 2014, as adjusted based on a modified performance period and modified performance goals, and were subject to the same service based vesting conditions as the performance share awards they replaced. These converted restricted stock unit awards were also subject to the Valuation Adjustment. As of December 31, 2016 , 736,911 of these restricted stock units remained outstanding. If an employee terminates employment before the service conditions lapse under the 2014 , 2015 or 2016 awards due to (1) Retirement or Disability (as defined in the award agreement), or (2) death, the service conditions will lapse on the date of such termination with respect to a pro rata portion of the restricted stock units and shares of restricted stock based upon the percentage of the service period satisfied between the grant date and the date of the termination of employment. In the event of a Change-in-Control (as defined in the award agreement), all unvested shares of restricted stock and restricted stock units awarded prior to 2014 will immediately vest and all unvested shares of restricted stock and restricted stock units awarded in 2014, 2015 and 2016 will immediately vest upon termination of employment occurring in connection with a Change-in-Control. Termination due to any other reason will result in all unvested shares of restricted stock and restricted stock units awarded being forfeited effective on the employee’s date of termination. (shares) Restricted Stock Units Weighted Average Grant Date Fair Value Per Unit ($) Nonvested at December 31, 2015 3,142,473 8.55 Granted 65,418 21.49 Forfeited (46,447 ) 11.71 Vested (1,519,414 ) 5.21 Nonvested at December 31, 2016 1,642,030 12.05 Performance Shares . In 2016 , NiSource granted 647,305 performance shares subject to service, performance and market conditions. The grant date fair value of the awards was $12.6 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 over the three year requisite service period. The performance conditions are based on achievement of certain non-GAAP financial measures: cumulative net operating earnings per share, a non-GAAP financial measure that NiSource defines as income from continuing operations adjusted for certain items, for the three-year period ending December 31, 2018; and relative total shareholder return, a non-GAAP market measure that NiSource defines as the annualized growth in dividends and share price of a share of NiSource's common stock (calculated using a 20 trading day average of NiSource's closing price beginning on December 31, 2015 and ending on December 31, 2018) compared to the total shareholder return performance of a predetermined peer group of companies. A Monte Carlo analysis was used to value the portion of these awards dependent on market conditions. As of December 31, 2016 , all 647,305 non-vested performance shares granted were outstanding. The service conditions for these awards lapse on February 28, 2019. In 2015 , NiSource did not grant any performance shares subject to performance and service conditions. In 2014 , NiSource granted 535,037 performance shares subject to performance and service conditions. The grant date fair-value of the awards was $16.6 million , based on the average market price of NiSource’s common stock at the date of each grant less the present value of dividends not received during the vesting period which will be expensed over the three year requisite service period. The performance conditions are based on achievement of certain non-GAAP financial measures: cumulative net operating earnings, which NiSource defines as income from continuing operations adjusted for certain items; and cumulative funds from operations, which NiSource defines as net operating cash flows provided by continuing operations, in each case for the three-year period ended December 31, 2016; and relative total shareholder return, a non-GAAP market measure that NiSource defines as the annualized growth in the dividends and share price of a share of NiSource’s common stock (calculated using a 20 trading day average of NiSource’s closing price beginning December 31, 2013 and ending on December 31, 2016) compared to the total shareholder return performance of a predetermined peer group of companies. The service conditions for these awards lapse on February 28, 2017. (shares) Performance Awards Weighted Average Grant Date Fair Value Per Unit ($) Nonvested at December 31, 2015 — — Granted 647,305 19.50 Forfeited — — Vested — — Nonvested at December 31, 2016 647,305 19.50 Non-employee Director Awards . As of May 11, 2010, awards to non-employee directors may be made only under the Omnibus Plan. Currently, restricted stock units are granted annually to non-employee directors, subject to a non-employee director’s election to defer receipt of such restricted stock unit award. The non-employee director’s restricted stock units vest on the last day of the non-employee director’s annual term corresponding to the year the restricted stock units were awarded subject to special pro-rata vesting rules in the event of Retirement or Disability (as defined in the award agreement), or death. The vested restricted stock units are payable as soon as practicable following vesting except as otherwise provided pursuant to the non-employee director’s election to defer. Certain restricted stock units remain outstanding from the Director Plan. All such awards are fully vested and shall be distributed to the directors upon their separation from the Board. As of December 31, 2016 , 218,581 restricted stock units are outstanding to non-employee directors under either the Omnibus Plan or the Director Plan. Of this amount, 40,932 restricted stock units are nonvested and expected to vest. 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 NiSource common stock. NiSource also has a retirement savings plan that provides for discretionary profit sharing contributions payable in shares of NiSource common stock to eligible employees based on earnings results; and eligible employees hired after January 1, 2010 receive a non-elective company contribution of 3% of eligible pay payable in shares of NiSource common stock. For the years ended December 31, 2016 , 2015 and 2014 , NiSource recognized 401(k) match, profit sharing and non-elective contribution expense of $32.3 million , $27.4 million and $28.1 million , respectively.

Long-Term Debt

Long-Term Debt	12 Months Ended
	Dec. 31, 2016
Long-term Debt, Current and Noncurrent [Abstract]
Long-Term Debt	Long-Term Debt NiSource long-term debt as of December 31, 2016 and 2015 is as follows: Long-term debt type Maturity Weighted average interest rate (%) Outstanding balance as of December 31, (in millions) 2016 2015 Senior notes: NiSource Finance March 2016 10.75 % $ — $ 201.5 NiSource Finance November 2016 5.41 % — 90.0 NiSource Finance September 2017 5.25 % 210.4 210.4 NiSource Finance March 2018 6.40 % 476.0 476.0 NiSource Finance January 2019 6.80 % 500.0 500.0 NiSource Finance March 2019 Variable (1) 500.0 — NiSource Finance September 2020 5.45 % 550.0 550.0 NiSource Finance December 2021 4.45 % 63.6 63.6 NiSource Finance March 2022 6.13 % 500.0 500.0 NiSource Finance February 2023 3.85 % 250.0 250.0 NiSource Finance November 2025 5.89 % 265.0 265.0 NiSource Finance December 2040 6.25 % 250.0 250.0 NiSource Finance June 2041 5.95 % 400.0 400.0 NiSource Finance February 2042 5.80 % 250.0 250.0 NiSource Finance February 2043 5.25 % 500.0 500.0 NiSource Finance February 2044 4.80 % 750.0 750.0 NiSource Finance February 2045 5.65 % 500.0 500.0 Capital Markets December 2027 6.78 % 3.0 3.0 Total senior notes $ 5,968.0 $ 5,759.5 Medium term notes: Columbia of Massachusetts December 2025 to February 2028 6.30 % $ 40.0 $ 40.0 Capital Markets March 2017 to May 2027 7.92 % 106.0 106.0 NIPSCO June 2017 to August 2027 7.57 % 95.5 95.5 Total medium term notes $ 241.5 $ 241.5 Capital leases: NiSource Corporate Services October 2019 to April 2021 2.92 % $ 3.5 $ 3.7 NIPSCO May 2018 3.95 % 12.7 52.8 Columbia of Ohio October 2021 to June 2038 6.53 % 80.1 79.8 Columbia of Massachusetts December 2033 to July 2036 5.33 % 23.7 24.1 Columbia of Virginia August 2024 to July 2029 12.27 % 5.5 5.8 Columbia of Pennsylvania August 2027 to June 2036 5.45 % 31.9 32.4 Total capital leases 157.4 198.6 Pollution control bonds - NIPSCO July 2017 to April 2019 5.76 % 96.0 226.0 Notes payable - NiSource Development Company July 2041 5.56 % — 2.1 Unamortized issuance costs and discounts (41.6 ) $ (45.5 ) Total Long-Term Debt 6,421.3 $ 6,382.2 (1) Rate of one month Libor plus 95 basis points. NiSource Finance is a 100% owned, consolidated finance subsidiary of NiSource that engages in financing activities to raise funds for the business operations of NiSource and its subsidiaries. NiSource Finance was incorporated in March 2000 under the laws of the state of Indiana. Prior to 2000, the function of NiSource Finance was performed by Capital Markets. NiSource Finance obligations are fully and unconditionally guaranteed by NiSource. Consequently, no separate financial statements for NiSource Finance are required to be reported. No NiSource subsidiaries guarantee debt. During 2016, NiSource Finance redeemed $291.5 million of fixed-rate long-term debt at maturity, entered into a $500 million term loan agreement and entered into forward starting swap-lock transactions with notional values totaling $500.0 million , while NIPSCO redeemed a total of $130.0 million of pollution control bonds. These transactions are detailed as follows: • On March 15, 2016, NiSource Finance redeemed $201.5 million of 10.75% senior unsecured notes at maturity. • On March 31, 2016, NiSource Finance entered into a $500 million term loan agreement with a syndicate of banks. The term loan matures March 29, 2019, at which point any and all outstanding borrowings under the agreement are due. Interest charged on borrowings depends on the variable rate structure elected by NiSource Finance at the time of each borrowing. The available variable rate structures from which NiSource Finance may choose are defined in the term loan agreement. As of December 31, 2016, NiSource Finance had $500.0 million of outstanding borrowings under the term loan agreement. • In June 2016, NiSource Finance entered into forward-starting interest rate swaps with an aggregate notional amount of $500.0 million to hedge the variability in cash flows attributable to changes in the benchmark interest rate during the period from the effective date of the swaps to the anticipated date of forecasted debt issuances, expected to take place by the end of 2018. The forward-starting interest rate swaps were designated as cash flow hedges at the time the agreements were executed, whereby any gain or loss recognized from the effective date of the swaps to the date the associated debt is issued for the effective portion of the hedge is recorded net of tax in AOCI and amortized as a component of interest expense over the life of the designated debt. If some portion of the hedges becomes ineffective, the associated gain or loss will be recognized in earnings. As of December 31, 2016, no ineffectiveness has been recorded. • On November 1, 2016, NIPSCO redeemed $130.0 million of 5.60% pollution control bonds at maturity. • On November 28, 2016, NiSource Finance redeemed $90.0 million of 5.41% senior unsecured notes at maturity. During 2015, NiSource Finance executed a $750.0 million tender offer on fixed-rate long-term debt, redeemed $230.0 million fixed-rate long-term debt at maturity, settled $1,075.0 million term loans, and entered into two forward starting swap-lock transactions with notional values totaling $1,000.0 million . These transactions are detailed as follows: • Prior to the Separation, CPG closed its placement of $2,750.0 million in aggregate principal amount of its senior notes. Using the proceeds from this offering, CPG made cash payments to NiSource representing the settlement of inter-company borrowings and the payment of a one-time special dividend. In May 2015, using proceeds from the cash payments from CPG, NiSource Finance settled its two bank term loans in the amount of $1,075.0 million and executed a tender offer for $750.0 million consisting of a combination of its 5.25% notes due 2017 , 6.40% notes due 2018 and 4.45% notes due 2021 . In conjunction with the debt retired, NiSource Finance recorded a $97.2 million loss on early extinguishment of long-term debt, primarily attributable to early redemption premiums. • On November 28, 2015, NiSource Finance redeemed $230.0 million of 5.36% senior unsecured notes at maturity. • In December 2015, NiSource Finance entered into forward starting interest rate swaps, with an aggregate notional amount of $1.0 billion , to hedge the variability in cash flows attributable to changes in the benchmark interest rate during the period from the effective date of the swap to the anticipated date of forecasted debt issuances by the end of 2018. The forward starting interest rate swaps were designated as cash flow hedges at the time the agreements were executed. See Note 18-A, "Contractual Obligations," for the outstanding long-term debt maturities at December 31, 2016 . Unamortized debt expense, premium and discount on long-term debt applicable to outstanding bonds are being amortized over the life of such bonds. NiSource is subject to a financial covenant under its revolving credit facility which requires NiSource to maintain a debt to capitalization ratio that does not exceed 70% . A similar covenant in a 2005 private placement note purchase agreement requires NiSource to maintain a debt to capitalization ratio that does not exceed 75% . As of December 31, 2016 , the ratio was 66% . NiSource is also subject to certain other non-financial covenants under the revolving credit facility. Such covenants include a limitation on the creation or existence of new liens on NiSource’s assets, generally exempting liens on utility assets, purchase money security interests, preexisting security interests and an additional subset of assets equal to $150 million . An asset sale covenant generally restricts the sale, conveyance, lease, transfer or other disposition of NiSource’s assets to those dispositions that are for a price not materially less than fair market of such assets, that would not materially impair the ability of NiSource and NiSource Finance to perform obligations under the revolving credit facility, and that together with all other such dispositions, would not have a material adverse effect. The covenant also restricts dispositions to no more than 10% of NiSource's consolidated total assets on December 31, 2015. The revolving credit facility also includes a cross-default provision, which triggers an event of default under the credit facility in the event of an uncured payment default relating to any indebtedness of NiSource or any of its subsidiaries in a principal amount of $50.0 million or more. NiSource’s indentures generally do not contain any financial maintenance covenants. However, NiSource’s indentures are generally subject to cross-default provisions ranging from uncured payment defaults of $5 million to $50 million , and limitations on the incurrence of liens on NiSource’s assets, generally exempting liens on utility assets, purchase money security interests, preexisting security interests and an additional subset of assets capped at 10% of NiSource’s consolidated net tangible assets.

Short-Term Borrowings

Short-Term Borrowings	12 Months Ended
	Dec. 31, 2016
Short-term Debt [Abstract]
Short-Term Borrowings	Short-Term Borrowings NiSource generates short-term borrowings from its revolving credit facility, commercial paper program, letter of credit issuances and accounts receivable transfer programs. Each of these borrowing sources is described further below. NiSource Finance maintains a revolving credit facility to fund ongoing working capital requirements including the provision of liquidity support for its $1.5 billion commercial paper program, provide for issuance of letters of credit and also for general corporate purposes. On November 28, 2016, NiSource Finance amended its existing revolving credit facility with a syndicate of banks led by Barclays Bank to increase the aggregate commitments from $1.5 billion to $1.85 billion and extend the termination date to November 28, 2021 . At December 31, 2016 and 2015, 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 and Wells Fargo. At December 31, 2016 , NiSource had $1,178.0 million of commercial paper outstanding. At December 31, 2015, NiSource had $321.4 million of commercial paper outstanding. As of December 31, 2016 and 2015, NiSource had $14.7 million of stand-by letters of credit outstanding all of which 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 Consolidated Balance Sheets in the amount of $310.0 million and $246.0 million as of December 31, 2016 and 2015 , respectively. Refer to Note 17, "Transfers of Financial Assets," for additional information. Short-term borrowings were as follows: At December 31, (in millions) 2016 2015 Commercial Paper weighted average interest rate of 1.24 % and 1.00% at December 31, 2016 and 2015, respectively. $ 1,178.0 $ 321.4 Accounts receivable securitization facility borrowings 310.0 246.0 Total Short-Term Borrowings $ 1,488.0 $ 567.4 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 Statements of Consolidated Cash Flows.

Fair Value

Fair Value	12 Months Ended
	Dec. 31, 2016
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 Consolidated Balance Sheets on a recurring basis and their level within the fair value hierarchy as of December 31, 2016 and December 31, 2015 : Recurring Fair Value Measurements December 31, 2016 ( in millions ) Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Balance as of December 31, 2016 Assets Risk management assets $ 5.4 $ 43.6 $ — $ 49.0 Available-for-sale securities — 131.5 — 131.5 Total $ 5.4 $ 175.1 $ — $ 180.5 Liabilities Risk management liabilities $ 1.2 $ 58.9 $ 1.2 $ 61.3 Total $ 1.2 $ 58.9 $ 1.2 $ 61.3 Recurring Fair Value Measurements December 31, 2015 ( in millions ) Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Balance as of December 31, 2015 Assets Risk management assets $ 0.1 $ — $ — $ 0.1 Available-for-sale securities — 128.7 — 128.7 Total $ 0.1 $ 128.7 $ — $ 128.8 Liabilities Risk management liabilities $ 14.3 $ 17.4 $ 0.2 $ 31.9 Total $ 14.3 $ 17.4 $ 0.2 $ 31.9 Risk management assets and liabilities include interest rate swaps, exchange-traded NYMEX futures and NYMEX options and non-exchange-based forward purchase 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 within 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 within 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 December 31, 2016 and 2015 , 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. NiSource Finance has entered into forward-starting interest rate swaps to hedge the interest rate risk on coupon payments of forecasted issuances of long-term debt. These swaps are designated as cash flow hedges. Credit risk is considered in the fair value calculation of each interest rate swap. As they are based on observable data and valuations of similar instruments, the interest rate swaps are categorized within Level 2 of the fair value hierarchy. There was no exchange of premium at the initial date of the swaps, and NiSource can settle the swaps at any time. For additional information see Note 9, "Risk Management Activities." 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 Consolidated Balance Sheets. NiSource values U.S. Treasury, corporate and mortgage-backed securities using a matrix pricing model that incorporates market-based information. These securities trade less frequently and are classified within Level 2. Total unrealized 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 securities at December 31, 2016 and 2015 were: December 31, 2016 (in millions) Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Available-for-sale securities U.S. Treasury debt securities $ 35.0 $ 0.1 $ (0.6 ) $ 34.5 Corporate/Other debt securities 98.7 0.3 (2.0 ) 97.0 Total $ 133.7 $ 0.4 $ (2.6 ) $ 131.5 December 31, 2015 (in millions) Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Available-for-sale securities U.S. Treasury debt securities $ 33.7 $ 0.1 $ (0.3 ) $ 33.5 Corporate/Other debt securities 95.7 0.3 (0.8 ) 95.2 Total $ 129.4 $ 0.4 $ (1.1 ) $ 128.7 For the years ended December 31, 2016 , 2015 , and 2014 , the realized gain on sale of available for sale U.S. Treasury debt securities was zero , $ 0.2 million and $ 0.1 million , respectively. For the years ended December 31, 2016 , 2015 , and 2014 , the realized gain on sale of available for sale Corporate/Other debt securities was $ 0.2 million , $ 0.2 million , and $ 0.4 million , respectively. The cost of maturities sold is based upon specific identification. At December 31, 2016 , approximately $0.5 million of U.S. Treasury securities have maturities of less than a year while the remaining securities have maturities of greater than one year. At December 31, 2016 , approximately $ 15.2 million of Corporate/Other debt securities 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 years ended December 31, 2016 and 2015 . Non-recurring Fair Value Measurements . There were no significant non-recurring fair value measurements recorded during the twelve months ended December 31, 2016 . 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 securities. 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 years ended December 31, 2016 and 2015 , there were no changes in the method or significant assumptions used to estimate the fair value of the financial instruments. The carrying amount and estimated fair values of financial instruments were as follows: At December 31, (in millions) Carrying Amount 2016 Estimated Fair Value 2016 Carrying Amount 2015 Estimated Fair Value 2015 Long-term debt (including current portion) $ 6,421.3 $ 7,064.1 $ 6,382.2 $ 6,975.7

Transfers Of Financial Assets

Transfers Of Financial Assets	12 Months Ended
	Dec. 31, 2016
Transfers and Servicing [Abstract]
Transfers Of Financial Assets	Transfers of Financial Assets 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 BTMU and a commercial paper conduit sponsored by BNS. T his agreement was last renewed on October 14, 2016; the current agreement expires on October 13, 2017, and can be further renewed if mutually agreed to by all parties. The maximum seasonal program limit under the terms of the current agreement is $240 million . As of December 31, 2016 , $100.0 million of accounts receivable had been transferred by CGORC. CGORC is a separate corporate entity from NiSource and Columbia of Ohio, with 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 PNC and Mizuho. This agreement was last renewed on August 24, 2016; the current agreement expires on August 23, 2017, and can be further renewed if mutually agreed to by all parties. The maximum seasonal program limit under the terms of the current agreement is $200 million . As of December 31, 2016 , $175.0 million of accounts receivable had been transferred by NARC. NARC is a separate corporate entity from NiSource and NIPSCO, with 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 agreement with BTMU was last renewed on March 9, 2016; the current agreement expires on March 8, 2017, and can be further renewed if mutually agreed to by both parties. The maximum seasonal program limit under the terms of the agreement is $75 million . As of December 31, 2016 , $35.0 million of accounts receivable had been transferred by CPRC. CPRC is a separate corporate entity from NiSource and Columbia of Pennsylvania, with 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. All accounts receivables sold to the purchasers 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. Transfers of accounts receivable are accounted for as secured borrowings resulting in the recognition of short-term borrowings on the Consolidated Balance Sheets. As of December 31, 2016 , the maximum amount of debt that can be recognized related to NiSource’s accounts receivable programs is $310.0 million . The following table reflects the gross and net receivables transferred as well as short-term borrowings related to the securitization transactions as of December 31, 2016 and 2015 for Columbia of Ohio, NIPSCO and Columbia of Pennsylvania: (in millions) December 31, December 31, Gross Receivables $ 618.3 $ 450.8 Less: Receivables not transferred 308.3 204.8 Net receivables transferred $ 310.0 $ 246.0 Short-term debt due to asset securitization $ 310.0 $ 246.0 During 2016 and 2015, $64.0 million and $38.3 million was recorded as cash flows from financing activities related to the change in short-term borrowings due to securitization transactions. Fees associated with the securitization transactions were $2.3 million , $2.5 million and $2.9 million for the years ended December 31, 2016 , 2015 and 2014, respectively. 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.

Other Commitments And Contingen

Other Commitments And Contingencies	12 Months Ended
	Dec. 31, 2016
Commitments and Contingencies Disclosure [Abstract]
Other Commitments And Contingencies	Other Commitments and Contingencies A. Contractual Obligations . NiSource has certain contractual obligations requiring payments at specified periods. The obligations include long-term debt, lease obligations, energy commodity contracts and obligations for various services including pipeline capacity and IBM outsourcing. The total contractual obligations in existence at December 31, 2016 and their maturities were: (in millions) Total 2017 2018 2019 2020 2021 After Long-term debt (1) $ 6,305.5 $ 349.9 $ 476.0 $ 1,041.0 $ 550.0 $ 63.6 $ 3,825.0 Capital leases (2) 250.0 22.7 18.5 14.2 13.5 13.4 167.7 Interest payments on long-term debt 4,611.2 337.9 305.3 265.2 244.9 214.9 3,243.0 Operating leases (3) 54.6 15.4 9.4 7.5 4.8 4.1 13.4 Energy commodity contracts (4) 312.1 108.5 67.7 67.3 68.0 0.6 — Service obligations: Pipeline service obligations 2,002.1 532.7 382.7 293.1 176.0 139.2 478.4 IBM service obligations 325.0 84.1 81.2 80.0 79.7 — — Other service obligations 77.7 58.1 17.4 1.9 0.3 — — Other liabilities 34.4 34.4 — — — — — Total contractual obligations $ 13,972.6 $ 1,543.7 $ 1,358.2 $ 1,770.2 $ 1,137.2 $ 435.8 $ 7,727.5 (1) Long-term debt balance excludes unamortized issuance costs and discounts of $41.6 million. (2) Capital lease payments shown above are inclusive of interest totaling $92.6 million. (3) Operating lease balances do not include amounts for fleet leases that can be renewed beyond the initial lease term. The Company anticipates renewing the leases beyond the initial term, but the anticipated payments associated with the renewals do not meet the definition of expected minimum lease payments and therefore are not included above. Expected payments are $31.1 million in 2017, $32.9 million in 2018, $26.1 million in 2019, $17.5 million in 2020, $8.0 million in 2021 and $2.0 million thereafter. (4) In January 2017, NIPSCO signed new coal contract commitments of $24.2 million and $10.1 million for 2017 and 2018, respectively. These contracts are not included above. Operating and Capital Lease Commitments. NiSource leases assets in several areas of its operations. Payments made in connection with operating leases were $ 52.0 million in 2016 , $ 47.5 million in 2015 and $ 59.8 million in 2014 , and are primarily charged to operation and maintenance expense as incurred. Capital lease assets and related accumulated depreciation included in the Consolidated Balance Sheets were $ 167.0 million and $ 20.6 million at December 31, 2016 , and $ 236.2 million and $ 44.0 million at December 31, 2015 , respectively. Included in capital leases are the adjusted payments for the NIPSCO service agreement with Pure Air. Refer to section E, "Other Matters," below for additional information. Purchase and Service Obligations. NiSource has entered into various purchase and service agreements whereby NiSource is contractually obligated to make certain minimum payments in future periods. NiSource’s purchase obligations are for the purchase of physical quantities of natural gas, electricity and coal. NiSource’s service agreements encompass a broad range of business support and maintenance functions which are generally described below. NiSource’s subsidiaries have entered into various energy commodity contracts to purchase physical quantities of natural gas, electricity and coal. These amounts represent minimum quantities of these commodities NiSource is obligated to purchase at both fixed and variable prices. In July 2008, the IURC issued an order approving NIPSCO’s purchase power agreements with subsidiaries of Iberdrola Renewables, Buffalo Ridge I LLC and Barton Windpower LLC. These agreements provide NIPSCO the opportunity and obligation to purchase up to 100 mw of wind power generated commencing in early 2009. The contracts extend 15 and 20 years, representing 50 mw of wind power each. No minimum quantities are specified within these agreements due to the variability of electricity generation from wind, so no amounts related to these contracts are included in the table above. Upon any termination of the agreements by NIPSCO for any reason (other than material breach by Buffalo Ridge I LLC or Barton Windpower LLC), NIPSCO may be required to pay a termination charge that could be material depending on the events giving rise to termination and the timing of the termination. NIPSCO began purchasing wind power in April 2009. NiSource has pipeline service agreements that provide for pipeline capacity, transportation and storage services. These agreements, which have expiration dates ranging from 2017 to 2045 , require NiSource to pay fixed monthly charges. NIPSCO has contracts with three major rail operators providing for coal transportation services for which there are certain minimum payments. These service contracts extend for various periods through 2018 . On December 31, 2013, NiSource Corporate Services signed a seven-year agreement with IBM to continue to provide business process and support functions to NiSource under a combination of fixed or variable charges, with the variable charges fluctuating based on the actual need for such services. The agreement was effective January 1, 2014 with a commencement date of April 1, 2014 and includes some targeted service enhancements as well as continued existing information technology support services and a few additional support services. NiSource has initiated a process to evaluate its future IT business process and support model, which included the issuance of a request for proposal from several service providers, including IBM. Upon any termination of the agreement by NiSource for any reason (other than material breach by IBM), NiSource may be required to pay IBM a termination charge that could include a breakage fee, repayment of IBM's capital investments not yet recovered and IBM's wind-down expense. This termination fee could be material depending on the events giving rise to the termination and the timing of the termination. B. 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. At December 31, 2016 , NiSource had issued stand-by letters of credit of $14.7 million for the benefit of third parties. C. Legal Proceedings . The Company is party to certain claims and legal proceedings arising in the ordinary course of business, none of which is deemed to be individually material at this time. Due to the inherent uncertainty of litigation, there can be no assurance that the resolution of any particular claim or proceeding would not have a material adverse effect on the Company’s results of operations, financial position or liquidity. If one or more of such matters were decided against the Company, the effects could be material to the Company’s results of operations in the period in which the Company would be required to record or adjust the related liability and could also be material to the Company’s cash flows in the periods the Company would be required to pay such liability. D. 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 the environmental regulations currently applicable to 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 December 31, 2016 and 2015 , NiSource had recorded a liability of approximately $111.4 million and $123.2 million , respectively, to cover environmental remediation at various sites. The current portion of this liability is included in "Legal and environmental" in the Consolidated Balance Sheets. The noncurrent portion is included in "Other noncurrent liabilities" in the Consolidated Balance Sheets. NiSource recognizes 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 remediation activities may 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 impact, the method of remediation and the availability of cost recovery. These expenditures are not currently estimable at some sites. NiSource periodically adjusts its liability as information is collected and estimates become more refined. Electric Operations' compliance estimates disclosed below are reflective of NIPSCO's Integrated Resource Plan submitted to the IURC on November 1, 2016. See section E, "Other Matters" below for additional information. 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 . Future legislative and regulatory programs, including implementation of the EPA CPP, could significantly limit allowed GHG emissions or impose a cost or tax on GHG emissions. Additionally, rules that increase methane leak detection, require emission reductions or impose additional requirements for natural gas facilities could restrict GHG emissions and impose additional costs. The CPP and other federally enacted or proposed GHG reduction measures are subject to numerous legal challenges that could change the way the programs are implemented, and NiSource will carefully monitor all GHG reduction proposals and regulations. National Ambient Air Quality Standards . The CAA requires the EPA to set NAAQS for six "criteria" air pollutants considered harmful to public health and the environment. Periodically, the EPA imposes new, or modifies existing, NAAQS. States containing areas that do not meet the new or revised standards, or contribute significantly to nonattainment of downwind states, may be required to take steps to achieve and maintain compliance with the standards. These steps could include additional pollution controls on boilers, engines, turbines and other facilities owned by electric generation and gas distribution operations. The following NAAQS were recently added or modified: Ozone. On October 26, 2015, the EPA issued a final rule to lower the 8-hour ozone standard from 75 ppb to 70 ppb. After the EPA proceeds with designations, areas where NiSource operates that are currently designated in attainment with the standards may be reclassified as nonattainment. NiSource will continue to monitor this matter and cannot estimate its impact at this time. Clean Power Plan. On October 23, 2015, the EPA issued a final rule to regulate CO 2 emissions from existing fossil-fuel EGUs under section 111(d) of the CAA. The final rule establishes national CO 2 emission-rate standards that are applied to each state’s mix of affected EGUs to establish state-specific emission-rate and mass-emission limits. The final rule requires each state to submit a plan indicating how the state will meet the EPA's emission-rate or mass-emission limit, including possibly imposing reduction obligations on specific units. If a state does not submit a satisfactory plan, the EPA will impose a federal plan on that state. On February 9, 2016, the U.S. Supreme Court stayed implementation of the CPP until litigation is decided on its merits. The cost to comply with this rule will depend on a number of factors, including the outcome of CPP litigation, the requirements of the state plan or final federal plan, and the level of NIPSCO's required CO 2 emission 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. NIPSCO will continue to monitor this matter and cannot estimate its impact at this time. Should costs be incurred to comply with the CPP, NIPSCO believes such costs will be eligible for recovery through customer rates. Waste CERCLA. NiSource subsidiaries are potentially responsible parties at waste disposal sites under the CERCLA (commonly known as Superfund) and similar state laws. Additionally, NiSource affiliates have retained environmental liabilities, including remediation liabilities, associated with certain former operations. MGP. 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 64 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 future remediation costs were noted as a result of the refresh completed as of June 30, 2016. The total estimated liability at NiSource related to the facilities subject to remediation was $105.5 million and $110.4 million at December 31, 2016 and 2015 , 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. CCRs. On April 17, 2015, the EPA issued a final rule for regulation of CCRs. The rule regulates CCRs under the RCRA Subtitle D, which determines them to be nonhazardous. The rule is implemented in phases and requires increased groundwater monitoring, reporting, record keeping and posting of related information to the Internet. The rule also establishes requirements related to CCR management and disposal. The rule will allow NIPSCO to continue its byproduct beneficial use program. The publication of the CCR rule resulted in revisions to previously recorded legal obligations associated with the retirement of certain NIPSCO facilities. The actual asset retirement costs related to the CCR rule may vary substantially from the estimates used to record the increased asset retirement obligation due to the uncertainty about the compliance strategies that will be used and the preliminary nature of available data used to estimate costs. Refer to Note 7, "Asset Retirement Obligations," for further information. In addition, to comply with the rule, NIPSCO will be required to incur future capital expenditures to modify its infrastructure and manage CCRs. Based upon a preliminary engineering study, capital compliance costs are currently expected to cost approximately $230 million . As allowed by the EPA, NIPSCO will continue to collect data over time to determine the specific compliance solutions and associated costs and, as a result, the actual costs may vary. NIPSCO has filed a petition with the IURC seeking approval of the projects and to recover the costs associated with CCR compliance. Water ELG. On November 3, 2015, the EPA issued a final rule to amend the ELG and standards for the Steam Electric Power Generating category. The final rule became effective January 4, 2016. The rule imposes new water treatment and discharge requirements on NIPSCO's electric generating facilities to be applied between 2018 and 2023. Based upon a preliminary engineering study, capital compliance costs are currently expected to cost approximately $170 million . NIPSCO has filed a petition with the IURC seeking approval of the projects and to recover the costs associated with ELG compliance. E. 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 agreed to reimburse NIPSCO for the total cost to construct transmission upgrades and place them into service, multiplied by a rate of 1.71 ("the multiplier"). On June 10, 2014, certain upgrade sponsors for both TUAs filed a complaint at the 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. On December 8, 2014, the FERC issued an order in response to the complaint finding that it is appropriate for NIPSCO to recover, through the multiplier, substantiated costs of ownership related to the TUAs. On August 10, 2016, NIPSCO reached settlement with all remaining parties to the complaint and filed with the FERC for approval. An order from the FERC approving the settlement was received on January 31, 2017. Receipt of the FERC order did not result in a material impact to the Consolidated Financial Statements. At the time the TUAs were executed, it was assumed the proceeds received from the upgrade sponsors would be taxable to NIPSCO. Accordingly, the multiplier included a provision for such taxes. On June 10, 2016, the U.S. Treasury Department issued a notice regarding transfers of property to regulated utilities by electric generators, stating that transfers within the scope of the notice will not be treated as taxable. In response to this notice, NIPSCO recorded a liability of $8.6 million to reflect the estimated amount owed to the upgrade sponsors for the portion of the multiplier previously collected for taxes. This activity is recorded within "Other, net" in the Statements of Consolidated Income (Loss). PHMSA Transmission. On March 17, 2016, PHMSA issued a proposed rule that would, if adopted, add new assessment and data requirements to existing transmission facilities that would necessitate expanded investigation and repair/replace activity on these facilities over the next 15 years. The comment period for the proposed rule closed on July 7, 2016. If adopted as proposed, this rule may require NiSource to incur significant incremental capital and operation and maintenance expenditures to achieve compliance. NiSource will continue to monitor this matter, and cannot reasonably estimate its impact at this time. PHMSA EFV. On October 14, 2016, PHMSA issued a final rule that expands safety requirements for EFVs. Among the rule's provisions is a requirement for utilities to notify customers whose service lines are not currently equipped with an EFV of their right to request installation of an EFV. The rule takes effect April 14, 2017. NiSource is evaluating potential impacts of this regulation on its operations and cannot reasonably estimate its impact at this time. NIPSCO 2016 Integrated Resource Plan. Environmental, regulatory and economic factors, including low natural gas prices and aging coal-fired units, have led NIPSCO to consider modifying its current electric generation supply mix to include less coal-fired generation. Due to enacted CCR and ELG legislation, NIPSCO would expect to incur over $1 billion in operating, maintenance, environmental and other costs over the next seven years if the current fleet of coal-fired generating units remain operational. On November 1, 2016, NIPSCO submitted its 2016 Integrated Resource Plan with the IURC. The plan evaluates demand-side and supply-side resource alternatives to reliably and cost effectively meet NIPSCO customers' future energy requirements over the next twenty years. The 2016 Integrated Resource Plan indicates that the most viable option for customers and NIPSCO involves the retirement of Bailly Generating Station (Units 7 and 8) as soon as mid-2018 and two units (Units 17 and 18) at the R.M. Schahfer Generating Station by the end of 2023. It is projected over the long term that the cost to customers to retire these units at these dates will be lower than maintaining and upgrading them for continuing generation. NiSource and NIPSCO committed to the retirement of the Bailly Generating Station units in connection with the filing of the 2016 Integrated Resource Plan. However, retirement of these units is subject to the approval of the MISO, which is responsible for coordinating, controlling and monitoring the use of the electric transmission system by utilities, generators and marketers across parts of 15 U.S. states and the Canadian province of Manitoba. In the fourth quarter of 2016, the MISO approved NIPSCO's plan to retire the Bailly Generating Station units by May 31, 2018. In accordance with ASC 980-360, the remaining net book value of the Bailly Generating Station units was reclassified from "Net utility plant" to "Other property, at cost, less accumulated depreciation" on the Consolidated Balance Sheets. Refer to Note 5, "Property, Plant and Equipment" for further information. In connection with the MISO's approval of NIPSCO's planned retirement of the Bailly Generating Station units, NiSource recorded $22.1 million of plant retirement-related charges in the fourth quarter of 2016. These charges were comprised of contract termination charges related to NIPSCO's capital lease with Pure Air (discussed further below), voluntary employee severance benefits, and write downs of certain materials and supplies inventory balances. These charges are presented within "Operation and maintenance" on the Statements of Consolidated Income. NIPSCO Pure Air. 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. Services under this contract commenced on July 1, 1992 and expired on June 30, 2012. The agreement was renewed effective July 1, 2012 for ten years requiring NIPSCO to pay for the services under a combination of fixed and variable charges. 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 $ 21.7 million and $ 19.5 million for the years ended December 31, 2016 and 2015 , respectively. In accordance with GAAP, the renewed agreement was evaluated to determine whether the arrangement qualifies as a lease. Based on the terms of the agreement, the arrangement qualified for capital lease accounting. As the effective date of the new agreement was July 1, 2012, NiSource capitalized this lease beginning in the third quarter of 2012. As further discussed above in this Note 18 under the heading "NIPSCO 2016 Integrated Resource Plan," NIPSCO plans to retire the generation station units serviced by Pure Air by May 31, 2018. In December 2016, as allowed by the provisions of the service agreement, NIPSCO provided Pure Air formal notice of intent to terminate the service agreement, effective May 31, 2018. Providing this notice to Pure Air triggered a contract termination liability of $16 million which was recorded in fourth quarter of 2016. This expense was included as part of the plant retirement-related charges discussed above. Payment of this liability is not due until NIPSCO ceases use of the scrubber services. The liability is presented in "Other noncurrent liabilities" on the Consolidated Balance Sheets. In addition, NIPSCO remeasured the remaining capital lease asset and obligation to reflect the change in estimated remaining minimum lease payments. This remeasurement was a non-cash transaction that had no impact on the Statements of Consolidated Income.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Loss	12 Months Ended
	Dec. 31, 2016
Components of Accumulated Other Comprehensive Income (Loss) [Abstract]
Accumulated Other Comprehensive Loss	Accumulated Other Comprehensive Loss The following table displays the activity of Accumulated Other Comprehensive Loss, net of tax: (in millions) Gains and Losses on 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 (loss) before reclassifications 0.9 (0.3 ) (10.2 ) (9.6 ) Amounts reclassified from accumulated other comprehensive loss (0.3 ) 2.5 0.4 2.6 Net current-period other comprehensive income (loss) 0.6 2.2 (9.8 ) (7.0 ) Balance as of December 31, 2014 $ 0.3 $ (23.6 ) $ (27.3 ) $ (50.6 ) Other comprehensive loss before reclassifications (0.5 ) (11.0 ) (5.0 ) (16.5 ) Amounts reclassified from accumulated other comprehensive loss (0.3 ) 3.2 2.6 5.5 Net current-period other comprehensive loss (0.8 ) (7.8 ) (2.4 ) (11.0 ) Allocation of AOCI to noncontrolling interest — 2.0 — 2.0 Distribution of CPG to shareholders (Refer to Note 3, "Discontinued Operations") — 13.9 10.6 24.5 Balance as of December 31, 2015 $ (0.5 ) $ (15.5 ) $ (19.1 ) $ (35.1 ) Other comprehensive income before reclassifications — 7.1 0.5 7.6 Amounts reclassified from accumulated other comprehensive loss (0.1 ) 1.5 1.0 2.4 Net current-period other comprehensive income (loss) (0.1 ) 8.6 1.5 10.0 Balance as of December 31, 2016 $ (0.6 ) $ (6.9 ) $ (17.6 ) $ (25.1 ) (1) All amounts are net of tax. Amounts in parentheses indicate debits.

Other, Net

Other, Net	12 Months Ended
	Dec. 31, 2016
Other Nonoperating Income (Expense) [Abstract]
Other, Net	Other, Net Year Ended December 31, (in millions) 2016 2015 2014 Interest Income $ 3.4 $ 0.8 $ 3.8 AFUDC Equity 11.6 11.5 10.7 Charitable Contributions (4.5 ) (4.8 ) (11.1 ) Miscellaneous (1) (9.0 ) 9.9 10.0 Total Other, net $ 1.5 $ 17.4 $ 13.4 (1) Miscellaneous in 2016 primarily consists of a TUA-related charge of $8.6 million to reflect the estimated amount owed to the upgrade sponsors for the portion of the multiplier previously collected for taxes. Refer to Note 18-E, "Other Matters," for additional information. In 2015 and 2014, Miscellaneous primarily consisted of TUA income.

Interest Expense, Net

Interest Expense, Net	12 Months Ended
	Dec. 31, 2016
Interest Expense [Abstract]
Interest Expense, Net	Interest Expense, Net Year Ended December 31, (in millions) 2016 2015 2014 Interest on long-term debt $ 352.3 $ 377.5 $ 368.6 Interest on short-term borrowings 9.2 2.2 5.2 Debt discount/cost amortization 7.6 8.7 8.0 Accounts receivable securitization fees 2.3 2.5 2.9 Allowance for borrowed funds used and interest capitalized during construction (5.6 ) (5.4 ) (5.3 ) Other (1) (16.3 ) (5.3 ) 0.1 Total Interest Expense, net $ 349.5 $ 380.2 $ 379.5 (1) The change in Other for 2016 is primarily attributed to increases in Columbia of Ohio's post-in-service carrying charges (PISCC).

Segments Of Business

Segments Of Business	12 Months Ended
	Dec. 31, 2016
Segment Reporting [Abstract]
Segments Of Business	Segments of Business At December 31, 2016 , NiSource’s operations are divided into two primary reportable 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 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. Year Ended December 31, (in millions) 2016 2015 2014 Gross Revenues Gas Distribution Operations Unaffiliated $ 2,818.2 $ 3,068.7 $ 3,593.6 Intersegment 12.4 0.4 0.3 Total 2,830.6 3,069.1 3,593.9 Electric Operations Unaffiliated 1,660.8 1,573.6 1,672.6 Intersegment 0.8 0.8 0.8 Total 1,661.6 1,574.4 1,673.4 Corporate and Other Unaffiliated 13.5 9.5 6.2 Intersegment 413.3 396.4 412.5 Total 426.8 405.9 418.7 Eliminations (426.5 ) (397.6 ) (413.6 ) Consolidated Gross Revenues $ 4,492.5 $ 4,651.8 $ 5,272.4 Year Ended December 31, (in millions) 2016 2015 2014 Operating Income (Loss) Gas Distribution Operations $ 574.0 $ 555.8 $ 537.0 Electric Operations 291.4 264.4 282.7 Corporate and Other (7.2 ) (20.3 ) (30.6 ) Consolidated Operating Income $ 858.2 $ 799.9 $ 789.1 Depreciation and Amortization Gas Distribution Operations $ 252.9 $ 232.6 $ 217.6 Electric Operations 274.5 267.7 244.4 Corporate and Other 19.7 24.1 24.9 Consolidated Depreciation and Amortization $ 547.1 $ 524.4 $ 486.9 Assets Gas Distribution Operations $ 11,096.4 $ 10,094.5 $ 9,443.7 Electric Operations 5,233.3 5,265.3 5,009.9 Corporate and Other (1) 2,362.2 2,132.7 10,136.2 Consolidated Assets $ 18,691.9 $ 17,492.5 $ 24,589.8 Capital Expenditures (2) Gas Distribution Operations $ 1,054.4 $ 917.0 $ 860.3 Electric Operations 420.6 400.3 438.8 Corporate and Other 15.4 50.2 40.5 Consolidated Capital Expenditures $ 1,490.4 $ 1,367.5 $ 1,339.6 (1) Corporate and Other in 2014 includes assets of Discontinued Operations. Refer to Note 3, "Discontinued Operations," for additional information. (2) Amounts differ from those presented on the Statements of Consolidated Cash Flows primarily due to the inclusion of capital expenditures included in current liabilities and AFUDC Equity.

Quarterly Financial Data

Quarterly Financial Data	12 Months Ended
	Dec. 31, 2016
Quarterly Financial Data [Abstract]
Quarterly Financial Data (Unaudited)	Quarterly Financial Data (Unaudited) Quarterly financial data does not always reveal the trend of NiSource’s business operations due to nonrecurring items and seasonal weather patterns, which affect earnings and related components of net revenues and operating income. (in millions, except per share data) First Quarter (1) Second Quarter (1) Third Quarter Fourth Quarter 2016 Gross revenues $ 1,436.6 $ 897.6 $ 861.3 $ 1,297.0 Operating Income 381.4 138.2 113.7 224.9 Income from Continuing Operations 186.6 29.0 23.7 88.8 Results from Discontinued Operations - net of taxes — (0.1 ) 3.5 — Net Income 186.6 28.9 27.2 88.8 Basic Earnings Per Share Continuing Operations 0.58 0.09 0.07 0.28 Discontinued Operations — — 0.01 — Basic Earnings Per Share $ 0.58 $ 0.09 $ 0.08 $ 0.28 Diluted Earnings Per Share Continuing Operations 0.58 0.09 0.07 0.27 Discontinued Operations — — 0.01 — Diluted Earnings Per Share $ 0.58 $ 0.09 $ 0.08 $ 0.27 2015 Gross revenues $ 1,852.2 $ 884.6 $ 817.2 $ 1,097.8 Operating Income 386.3 84.4 109.7 219.5 Income (Loss) from Continuing Operations 192.5 (73.1 ) 14.8 64.4 Results from Discontinued Operations - net of taxes (2) 82.8 45.4 (19.7 ) (5.0 ) Net Income (Loss) 275.3 (27.7 ) (4.9 ) 59.4 Net Income (Loss) attributable to NiSource 268.4 (36.4 ) (4.9 ) 59.4 Basic Earnings (Loss) Per Share Continuing Operations 0.61 (0.23 ) 0.05 0.20 Discontinued Operations 0.24 0.12 (0.07 ) (0.01 ) Basic Earnings (Loss) Per Share $ 0.85 $ (0.11 ) $ (0.02 ) $ 0.19 Diluted Earnings (Loss) Per Share Continuing Operations 0.61 (0.23 ) 0.05 0.20 Discontinued Operations 0.24 0.12 (0.07 ) (0.01 ) Diluted Earnings (Loss) Per Share $ 0.85 $ (0.11 ) $ (0.02 ) $ 0.19 (1) First and second quarter results for 2016 differ from the results presented in the as-filed Form 10-Q for the respective periods as a result of the adoption of ASU 2016-09 in the third quarter of 2016 . Refer to Note 2, "Recent Accounting Pronouncements," for additional information. (2) Includes the results of the former Columbia Pipeline Group segment.

Supplemental Cash Flow Informat

Supplemental Cash Flow Information	12 Months Ended
	Dec. 31, 2016
Supplemental Cash Flow Information [Abstract]
Supplemental Cash Flow Information	Supplemental Cash Flow Information The following tables provide additional information regarding NiSource’s Consolidated Statements of Cash Flows for the years ended December 31, 2016 , 2015 and 2014 : Year Ended December 31, (in millions) 2016 2015 2014 Supplemental Disclosures of Cash Flow Information Non-cash transactions: Capital expenditures included in current liabilities $ 125.3 $ 121.6 $ 127.4 Assets acquired under a capital lease 4.0 47.5 76.7 Schedule of interest and income taxes paid: Cash paid for interest, net of interest capitalized amounts $ 337.8 $ 390.4 $ 429.3 Cash paid for income taxes 8.0 21.3 19.4

Valuation And Qualifying Accoun

Valuation And Qualifying Accounts	12 Months Ended
	Dec. 31, 2016
Valuation and Qualifying Accounts [Abstract]
Schedule of Valuation and Qualifying Accounts Disclosure	NISOURCE INC. SCHEDULE II – VALUATION AND QUALIFYING ACCOUNTS Twelve months ended December 31, 2016 Additions ($ in millions) Balance Jan. 1, 2016 Charged to Costs and Expenses Charged to Other Account (1) Deductions for Purposes for which Reserves were Created Balance Dec. 31, 2016 Reserves Deducted in Consolidated Balance Sheet from Assets to Which They Apply: Reserve for accounts receivable $ 20.3 $ 19.7 $ 48.5 $ 65.2 $ 23.3 Reserve for other investments 3.0 — — — 3.0 Twelve months ended December 31, 2015 Additions ($ in millions) Balance Charged to Costs and Expenses Charged to Other Account (1) Deductions for Purposes for which Reserves were Created Balance Reserves Deducted in Consolidated Balance Sheet from Assets to Which They Apply: Reserve for accounts receivable $ 24.9 $ 22.5 $ 56.7 $ 83.8 $ 20.3 Reserve for other investments 3.0 — — — 3.0 Twelve months ended December 31, 2014 Additions ($ in millions) Balance Charged to Costs and Expenses Charged to Other Account (1) Deductions for Purposes for which Reserves were Created Balance Reserves Deducted in Consolidated Balance Sheet from Assets to Which They Apply: Reserve for accounts receivable $ 23.4 $ 21.8 $ 69.9 $ 90.2 $ 24.9 Reserve for other investments 3.0 — — — 3.0 (1) Charged to Other Accounts reflects the deferral of bad debt expense to a regulatory asset.

Nature Of Operations And Summ35

Nature Of Operations And Summary Of Significant Accounting Policies (Policy)	12 Months Ended
	Dec. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Company Structure And Principles Of Consolidation	Company Structure and Principles of Consolidation . NiSource, a Delaware corporation headquartered in Merrillville, Indiana, is an energy holding company whose subsidiaries are fully regulated natural gas and electric utility companies serving approximately 3.9 million customers in seven states. NiSource generates substantially all of its operating income through these rate-regulated businesses. The consolidated financial statements include the accounts of NiSource and its majority-owned subsidiaries after the elimination of all intercompany accounts and transactions.
Use Of Estimates	Use of Estimates. The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.
Cash, Cash Equivalents, And Restricted Cash	Cash, Cash Equivalents and Restricted Cash . NiSource considers all highly liquid investments with original maturities of three months or less to be cash equivalents. NiSource reports amounts deposited in brokerage accounts for margin requirements as restricted cash. In addition, NiSource has amounts deposited in trust to satisfy requirements for the provision of various property, liability, workers compensation, and long-term disability insurance, which is classified as restricted cash and disclosed as an investing cash flow on the Statements of Consolidated Cash Flows.
Accounts Receivable And Unbilled Revenue	Accounts Receivable and Unbilled Revenue. Accounts receivable on the Consolidated Balance Sheets includes both billed and unbilled amounts. Unbilled amounts of accounts receivable relate to a portion of a customer’s consumption of gas or electricity from the date of the last cycle billing date through the last day of the month (balance sheet date). Factors taken into consideration when estimating unbilled revenue include historical usage, customer rates and weather. Accounts receivable fluctuates from year to year depending in large part on weather impacts and price volatility. NiSource's accounts receivable on the Consolidated Balance Sheets include unbilled revenue, less reserves, in the amounts of $329.7 million and $237.1 million as of December 31, 2016 and 2015, respectively. The reserve for uncollectible receivables is the Company’s best estimate of the amount of probable credit losses in the existing accounts receivable. The Company determined the reserve based on historical experience and in consideration of current market conditions. Account balances are charged against the allowance when it is anticipated the receivable will not be recovered.
Investments In Debt And Equity Securities	Investments in Debt Securities. NiSource’s investments in debt securities are carried at fair value and are designated as available-for-sale. These investments are included within “Other investments” on the Consolidated Balance Sheets. Unrealized gains and losses, net of deferred income taxes, are reflected as accumulated other comprehensive income (loss). These investments are monitored for other than temporary declines in market value. Realized gains and losses and permanent impairments are reflected in the Statements of Consolidated Income. No material impairment charges were recorded for the years ended December 31, 2016 , 2015 or 2014 . Refer to Note 16, "Fair Value," for additional information.
Basis Of Accounting For Rate-Regulated Subsidiaries	Basis of Accounting for Rate-Regulated Subsidiaries . Rate-regulated subsidiaries account for and report assets and liabilities consistent with the economic effect of the way in which regulators establish rates, if the rates established are designed to recover the costs of providing the regulated service and it is probable that such rates can be charged and collected. Certain expenses and credits subject to utility regulation or rate determination normally reflected in income are deferred on the Consolidated Balance Sheets and are recognized in income as the related amounts are included in customer rates and recovered from or refunded to customers. In the event that regulation significantly changes the opportunity for NiSource to recover its costs in the future, all or a portion of NiSource’s regulated operations may no longer meet the criteria for regulatory accounting. In such an event, a write-down of all or a portion of NiSource’s existing regulatory assets and liabilities could result. If transition cost recovery was approved by the appropriate regulatory bodies that would meet the requirements under GAAP for continued accounting as regulatory assets and liabilities during such recovery period, the regulatory assets and liabilities would be reported at the recoverable amounts. If unable to continue to apply the provisions of regulatory accounting, NiSource would be required to apply the provisions of ASC 980-20, Discontinuation of Rate-Regulated Accounting . In management’s opinion, NiSource’s regulated subsidiaries will be subject to regulatory accounting for the foreseeable future. Refer to Note 8, "Regulatory Matters," for additional information.
Utility Plant And Other Property And Related Depreciation And Maintenance	Plant and Other Property and Related Depreciation and Maintenance . Property, plant and equipment (principally utility plant) is stated at cost. The rate-regulated subsidiaries record depreciation using composite rates on a straight-line basis over the remaining service lives of the electric, gas and common properties as approved by the appropriate regulators. Non-utility property is generally depreciated on a straight-line basis over the life of the associated asset. Refer to Note 5, "Property, Plant and Equipment," for additional information related to depreciation expense at Units 7 and 8 at Bailly Generating Station. For rate-regulated companies, AFUDC is capitalized on all classes of property except organization costs, land, autos, office equipment, tools and other general property purchases. The allowance is applied to construction costs for that period of time between the date of the expenditure and the date on which such project is placed in service. The pre-tax rate for AFUDC was 4.5% in 2016 , 4.7% in 2015 and 4.5% in 2014 . Generally, NiSource’s subsidiaries follow the practice of charging maintenance and repairs, including the cost of removal of minor items of property, to expense as incurred. When NiSource’s subsidiaries retire regulated property, plant and equipment, original cost plus the cost of retirement, less salvage value, is charged to accumulated depreciation. However, when it becomes probable a regulated asset will be retired substantially in advance of its original expected useful life or is abandoned, the cost of the asset and the corresponding accumulated depreciation is recognized as a separate asset. If the asset is still in operation, the net amount is classified as "Other property, at cost, less accumulated depreciation" on the Consolidated Balance Sheets. If the asset is no longer operating, the net amount is classified in "Regulatory assets" on the Consolidated Balance Sheets. If NiSource is able to recover a full return on investment, the carrying value of the asset is based on historical cost. If NiSource is not able to recover a full return on investment, a loss on impairment is recognized to the extent the net book value of the asset exceeds the present value of future revenues discounted at the incremental borrowing rate. When NiSource’s subsidiaries sell entire regulated operating units, or retire or sell nonregulated properties, the original cost and accumulated depreciation and amortization balances are removed from "Property, Plant and Equipment" on the Consolidated Balance Sheets. Any gain or loss is recorded in earnings, unless otherwise required by the applicable regulatory body. Refer to Note 5, "Property, Plant and Equipment," for further information. External and internal costs associated with computer software developed for internal use are capitalized. Capitalization of such costs commences upon the completion of the preliminary stage of each project. Once the installed software is ready for its intended use, such capitalized costs are amortized on a straight-line basis generally over a period of five years, except for certain significant enterprise-wide technology investments which are amortized over a ten-year period.
Goodwill And Other Intangible Assets	Goodwill and Other Intangible Assets. Substantially all of NiSource's goodwill relates to the excess of cost over the fair value of the net assets acquired in the Columbia acquisition on November 1, 2000. NiSource tests its goodwill for impairment annually as of May 1st, or more frequently if events and circumstances indicate that goodwill might be impaired. Fair value of NiSource's reporting units is determined using a combination of income and market approaches. NiSource has other intangible assets consisting primarily of franchise rights apart from goodwill that were identified as part of the purchase price allocations associated with the acquisition of Columbia of Massachusetts which is being amortized on a straight-line basis over forty years from the date of acquisition. See Note 6, "Goodwill and Other Intangible Assets," for additional information
Revenue Recognition	Revenue Recognition. Revenue is recorded as products and services are delivered. Utility revenues are billed to customers monthly on a cycle basis. Revenues are recorded on the accrual basis and also include estimates for electricity and gas delivered but not billed. The accruals for unbilled revenues are reversed in the subsequent accounting period when meters are actually read and customers are billed. On occasion, NiSource's regulated subsidiaries are permitted to implement new rates that have not been formally approved by their state regulatory commissions, which are subject to refund. As permitted by accounting principles generally accepted in the United States, each regulated subsidiary recognizes this revenue and establishes a reserve for amounts that could be refunded based on its experience for the jurisdiction in which the rates were implemented. In connection with such revenues, estimated rate refund liabilities are recorded which reflect management’s current judgment of the ultimate outcomes of the proceedings. No provisions are made when, in the opinion of management, the facts and circumstances preclude a reasonable estimate of the outcome.
Accounts Receivable Transfer Program	Accounts Receivable Transfer Program. Certain of NiSource’s subsidiaries have agreements with third parties to sell certain accounts receivable without recourse. These transfers of accounts receivable are accounted for as secured borrowings. The entire gross receivables balance remains on the December 31, 2016 and 2015 Consolidated Balance Sheets and short-term debt is recorded in the amount of proceeds received from the purchasers involved in the transactions. Refer to Note 17, "Transfers of Financial Assets," for further information.
Fuel Adjustment Clause	Gas Cost and Fuel Adjustment Clause. NiSource’s regulated subsidiaries defer most differences between gas and fuel purchase costs and the recovery of such costs in revenues, and adjust future billings for such deferrals on a basis consistent with applicable state-approved tariff provisions. These deferred balances are recorded as regulatory assets or regulatory liabilities, as appropriate, on the Consolidated Balance Sheets. Refer to Note 8, "Regulatory Matters," for additional information.
Gas Inventory	Inventory. Both the LIFO inventory methodology and the weighted average cost methodology are used to value natural gas in storage, as approved by regulators for all of NiSource’s regulated subsidiaries. Inventory valued using LIFO was $46.1 million and $50.2 million at December 31, 2016 and 2015 , respectively. Based on the average cost of gas using the LIFO method, the estimated replacement cost of gas in storage was less than the stated LIFO cost by $9.4 million and $27.2 million at December 31, 2016 and 2015 , respectively. Gas inventory valued using the weighted average cost methodology was $233.8 million at December 31, 2016 and $293.3 million at December 31, 2015 . Electric production fuel is valued using the weighted average cost inventory methodology, as approved by NIPSCO's regulator. Electric production fuel balances were $112.8 million at December 31, 2016 and $106.3 million at December 31, 2015 . Materials and supplies are valued using the weighted average cost inventory methodology. Materials and supplies balances were $101.7 million at December 31, 2016 and $86.8 million at December 31, 2015 .
Accounting For Exchange And Balancing Arrangements Of Natural Gas	Accounting for Exchange and Balancing Arrangements of Natural Gas. NiSource’s Gas Distribution Operations segment enters into balancing and exchange arrangements of natural gas as part of its operations and off-system sales programs. NiSource records a receivable or payable for any of its respective cumulative gas imbalances, as well as for any gas inventory borrowed or lent under a Gas Distributions Operations exchange agreement. These receivables and payables are recorded as “Exchange gas receivable” or “Exchange gas payable” on NiSource’s Consolidated Balance Sheets, as appropriate.
Accounting For Risk Management Activities	Accounting for Risk Management Activities. NiSource accounts for its derivatives and hedging activities in accordance with ASC 815. NiSource recognizes all derivatives as either assets or liabilities on the Consolidated Balance Sheets at fair value, unless such contracts are exempted as a normal purchase normal sale under the provisions of the standard. The accounting for changes in the fair value of a derivative depends on the intended use of the derivative and resulting designation. NiSource has elected not to net fair value amounts for any of its derivative instruments or the fair value amounts recognized for its right to receive cash collateral or obligation to pay cash collateral arising from those derivative instruments recognized at fair value, which are executed with the same counterparty under a master netting arrangement. See Note 9, "Risk Management Activities," for additional information.
Income Taxes And Investment Tax Credits	Income Taxes and Investment Tax Credits. NiSource records income taxes to recognize full interperiod tax allocations. Under the asset and liability method, deferred income taxes are provided for the tax consequences of temporary differences by applying enacted statutory tax rates applicable to future years to differences between the financial statement carrying amount and the tax basis of existing assets and liabilities. Previously recorded investment tax credits of the regulated subsidiaries were deferred on the balance sheet and are being amortized to book income over the regulatory life of the related properties to conform to regulatory policy. To the extent certain deferred income taxes of the regulated companies are recoverable or payable through future rates, regulatory assets and liabilities have been established. Regulatory assets for income taxes are primarily attributable to property-related tax timing differences for which deferred taxes had not been provided in the past, when regulators did not recognize such taxes as costs in the ratemaking process. Regulatory liabilities for income taxes are primarily attributable to the regulated companies’ obligation to refund to ratepayers deferred income taxes provided at rates higher than the current Federal income tax rate. Such amounts are credited to ratepayers using either the average rate assumption method or the reverse South Georgia method. Pursuant to the U.S. Internal Revenue Code and relevant state taxing authorities, NiSource and its subsidiaries file consolidated income tax returns for Federal and certain state jurisdictions. NiSource and its subsidiaries are parties to an agreement (the “Intercompany Income Tax Allocation Agreement”) that provides for the allocation of consolidated tax liabilities. The Intercompany Income Tax Allocation Agreement generally provides that each party is allocated an amount of tax similar to that which would be owed had the party been separately subject to tax.
Environmental Expenditures	Environmental Expenditures. NiSource accrues for costs associated with environmental remediation obligations when the incurrence of such costs is probable and the amounts can be reasonably estimated, regardless of when the expenditures are actually made. The undiscounted estimated future expenditures are based on currently enacted laws and regulations, existing technology and estimated site-specific costs where assumptions may be made about the nature and extent of site contamination, the extent of cleanup efforts, costs of alternative cleanup methods and other variables. The liability is adjusted as further information is discovered or circumstances change. The reserves for estimated environmental expenditures are recorded on the Consolidated Balance Sheets in “Legal and environmental” for short-term portions of these liabilities and “Other noncurrent liabilities” for the respective long-term portions of these liabilities. Rate-regulated subsidiaries applying regulatory accounting establish regulatory assets on the Consolidated Balance Sheets to the extent that future recovery of environmental remediation costs is probable through the regulatory process. Refer to Note 18, "Other Commitments and Contingencies," for further information.
Excise Taxes	Excise Taxes. NiSource accounts for excise taxes that are customer liabilities by separately stating on its invoices the tax to its customers and recording amounts invoiced as liabilities payable to the applicable taxing jurisdiction. Such balances are presented within "Other accruals" on the Consolidated Balance Sheets. These types of taxes collected from customers, comprised largely of sales taxes, are presented on a net basis affecting neither revenues nor cost of sales. NiSource accounts for excise taxes for which it is liable by recording a liability for the expected tax with a corresponding charge to “Other taxes” expense on the Statements of Consolidated Income.
Accrued Insurance Liabilities	Accrued Insurance Liabilities. NiSource accrues for insurance costs related to workers compensation, automobile, property, general and employment practices liabilities based on the most probable value of each claim. Claim values are determined by professional, licensed loss adjusters who consider the facts of the claim, anticipated indemnification and legal expenses, and respective state rules. Claims are reviewed by NiSource at least quarterly and an adjustment is made to the accrual based on the most current information. NiSource’s actual exposure to liability is minimal due to coverage from its wholly-owned captive insurer who then re-insures risk to third party insurance providers for the majority of costs paid to claimants above NiSource's deductible.

Recent Accounting Pronounceme36

Recent Accounting Pronouncements (Tables)	12 Months Ended
	Dec. 31, 2016
Recent Accounting Pronouncements [Abstract]
Description of New Accounting Pronouncements Not yet Adopted	NiSource is currently evaluating the impact of certain ASUs on its Consolidated Financial Statements or Notes to Consolidated Financial Statements, which are described below: Standard Description Effective date Effect on the financial statements or other significant matters ASU 2017-04, Intangibles - Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment The pronouncement simplifies the calculation of goodwill impairment charges by eliminating the the requirement to perform the "Step 2" analysis when the "Step 1" test is failed. Annual periods beginning after December 15, 2019, including interim periods therein. Early adoption is permitted for annual or interim periods beginning after January 1, 2017. NiSource elected to adopt this ASU effective January 1, 2017. The adoption of this standard did not have a material impact on the Consolidated Financial Statements or Notes to Consolidated Financial Statements. ASU 2016-18, Statement of Cash Flows (Topic 230): Restricted Cash (a consensus of the FASB Emerging Issues Task Force) The pronouncement provides clarification on the classification and presentation of restricted cash in the Statements of Consolidated Cash Flows. Annual periods beginning after December 15, 2017, including interim periods therein. Early adoption is permitted. Upon adoption, restricted cash on the Statements of Consolidated Cash Flows will no longer be presented as an investing activity and will instead be included as a component of beginning and ending cash. NiSource expects to adopt this ASU effective January 1, 2018. ASU 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments (a consensus of the Emerging Issues Task Force) The pronouncement provides specific guidance on eight cash flow classification issues to reduce the diversity in practice. Annual periods beginning after December 15, 2017, including interim periods therein. Early adoption is permitted. NiSource does not anticipate the adoption of this standard will have a material impact on the Consolidated Financial Statements or Notes to Consolidated Financial Statements. NiSource expects to adopt this ASU effective January 1, 2018. Standard Description Effective date Effect on the financial statements or other significant matters ASU 2016-13, Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments The pronouncement changes the impairment model for most financial assets, replacing the current "incurred loss" model. ASU 2016-13 will require the use of an "expected loss" model for instruments measured at amortized cost and will also require entities to record allowances for available-for-sale debt securities rather than reduce the carrying amount. Annual periods beginning after December 15, 2019, including interim periods therein. Early adoption is permitted for annual or interim periods beginning after December 15, 2018. NiSource is currently evaluating the impact of adoption, if any, on the Consolidated Financial Statements and Notes to Consolidated Financial Statements. ASU 2016-12, Revenue from Contracts with Customers (Topic 606): Narrow-Scope Improvements and Practical Expedients The pronouncement clarifies implementation guidance in ASU 2014-09 on assessing collectability, noncash consideration and the presentation of sales and other similar taxes collected from customers. Annual periods beginning after December 15, 2017, including interim periods therein. Early adoption is permitted for annual or interim periods beginning after December 15, 2016. NiSource has formed an internal stakeholder group to promote information sharing and communication of the new requirements. Additionally, NiSource participates in an informal forum of industry peers where questions can be asked and interpretations of the new standard can be shared. NiSource has separated its various revenue streams into high-level categories, which will serve as the basis for accounting analysis and documentation as it relates to the pronouncement's impact on NiSource's revenues. Substantially all of NiSource’s revenues are tariff based, which NiSource believes will be in scope of ASC 606. NiSource expects to adopt this ASU effective January 1, 2018. As of December 31, 2016, NiSource has not concluded on a method of adoption. ASU 2016-08, Revenue from Contracts with Customers (Topic 606): Principal versus Agent Considerations The pronouncement clarifies the principal versus agent guidance in ASU 2014-09. The amendment clarifies how an entity should identify the unit of accounting for the principal versus agent evaluation, and how it should apply the control principle to certain types of arrangements. ASU 2014-09, Revenue from Contracts with Customers (Topic 606) The pronouncement 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. ASU 2016-02, Leases (Topic 842) The pronouncement introduces a lessee model that brings most leases on the balance sheet. The standard requires that lessees recognize the following for all leases (with the exception of short-term leases, as that term is defined in the standard) at the lease commencement date: (1) a lease liability, which is a lessee’s obligation to make lease payments arising from a lease, measured on a discounted basis; and (2) a right-of-use asset, which is an asset that represents the lessee’s right to use, or control the use of, a specified asset for the lease term. Annual periods beginning after December 15, 2018, including interim periods therein. Early adoption is permitted. NiSource has formed an internal stakeholder group that meets periodically to share information and gather data related to leasing activity at NiSource. This includes compiling a list of all contracts that could meet the definition of a lease under the new standard and evaluating the accounting for these contracts under the new standard to determine the ultimate impact the new standard will have on NiSource’s financial statements. Also this procedure has identified process improvements to ensure data from newly initiated leases is captured to comply with the new standard. This work is ongoing with the assistance of a third-party advisory firm. As of December 31, 2016, no conclusion has been reached as to when NiSource will adopt this standard. ASU 2016-01, Financial Instruments (Topic 825): Recognition and Measurement of Financial Assets and Financial Liabilities The pronouncement makes limited amendments to the guidance in GAAP on the classification and measurement of financial instruments. The standard requires entities to measure equity investments that do not result in consolidation and are not accounted for under the equity method at fair value and recognize any changes in fair value in net income unless the investments qualify for the new practicability exception. Annual periods beginning after December 15, 2017, including interim periods therein. Early adoption is permitted. NiSource is currently evaluating the impact of adoption, if any, on the Consolidated Financial Statements and Notes to Consolidated Financial Statements.
Schedule of New Accounting Pronouncements and Changes in Accounting Principles	The table below includes ASUs NiSource adopted during 2016: Standard Adoption ASU 2016-09, Compensation-Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting NiSource elected to adopt this pronouncement during the third quarter of 2016. Upon adoption, NiSource elected to begin accounting for forfeitures of share-based awards as they occur. The impact of this change was not material. Additionally, NiSource recorded a $25.3 million credit to beginning retained deficit. This adjustment represents excess tax benefits generated in years prior to 2016 that were previously not recognized in stockholders' equity due to NOLs in those years. Both of these adjustments were adopted on a modified retrospective basis. Lastly, NiSource recorded income tax benefits of $7.2 million related to excess tax benefits generated in 2016. This provision was adopted on a prospective basis. However, because NiSource adopted the standard during an interim period, the standard required this $7.2 million benefit be reflected as though it was adopted as of January 1, 2016.

Discontinued Operations (Tables

Discontinued Operations (Tables)	12 Months Ended
	Dec. 31, 2016
Discontinued Operations and Disposal Groups [Abstract]
Schedule of Discontinued Operations	Year Ended December 31, 2015 (in millions) Columbia Pipeline Group Operations Corporate and Other Total Net Revenues Transportation and storage revenues $ 561.4 $ — $ 561.4 Other revenues 94.3 — 94.3 Total Sales Revenues 655.7 — 655.7 Less: Cost of sales (excluding depreciation and amortization) 0.2 — 0.2 Net Revenues 655.5 — 655.5 Operating Expenses Operation and maintenance 375.8 (1) — 375.8 Depreciation and amortization 66.4 — 66.4 Gain on sale of assets (13.6 ) — (13.6 ) Other taxes 38.0 — 38.0 Total Operating Expenses 466.6 — 466.6 Equity Earnings in Unconsolidated Affiliates 29.1 — 29.1 Operating Income from Discontinued Operations 218.0 — 218.0 Other Income (Deductions) Interest expense, net (37.1 ) — (37.1 ) Other, net 7.8 0.4 8.2 Total Other Income (Deductions) (29.3 ) 0.4 (28.9 ) Income from Discontinued Operations before Income Taxes 188.7 0.4 189.1 Income Taxes 84.7 0.9 85.6 Income (Loss) from Discontinued Operations - net of taxes $ 104.0 $ (0.5 ) $ 103.5 (1) Includes approximately $55.4 million of transaction costs related to the Separation. Year Ended December 31, 2014 (in millions) Columbia Pipeline Group Operations Corporate and Other Total Net Revenues Transportation and storage revenues $ 1,034.3 $ — $ 1,034.3 Other revenues 312.9 — 312.9 Total Sales Revenues 1,347.2 — 1,347.2 Less: Cost of sales (excluding depreciation and amortization) 0.3 — 0.3 Net Revenues 1,346.9 — 1,346.9 Operating Expenses Operation and maintenance 769.1 (1) — 769.1 Depreciation and amortization 118.6 — 118.6 Gain on sale of assets (34.5 ) — (34.5 ) Other taxes 67.1 — 67.1 Total Operating Expenses 920.3 — 920.3 Equity Earnings in Unconsolidated Affiliates 46.6 — 46.6 Operating Income from Discontinued Operations 473.2 — 473.2 Other Income (Deductions) Interest expense, net (64.1 ) — (64.1 ) Other, net 8.9 (1.0 ) 7.9 Total Other Income (Deductions) (55.2 ) (1.0 ) (56.2 ) Income (Loss) from Discontinued Operations before Income Taxes 418.0 (1.0 ) 417.0 Income Taxes 143.5 (0.3 ) 143.2 Income (Loss) from Discontinued Operations - net of taxes $ 274.5 $ (0.7 ) $ 273.8 (1) Includes approximately $23.7 million of transaction costs related to the Separation.

Earnings Per Share (Tables)

Earnings Per Share (Tables)	12 Months Ended
	Dec. 31, 2016
Earnings Per Share [Abstract]
Schedule of Weighted Average Number of Shares	The computation of diluted average common shares is as follows: Year Ended December 31, (in thousands) 2016 2015 2014 Denominator Basic average common shares outstanding 321,805 317,746 315,120 Dilutive potential common shares: Nonqualified stock options — — 6 Shares contingently issuable under employee stock plans 165 — 1,066 Shares restricted under stock plans 1,554 2,090 444 Diluted Average Common Shares 323,524 319,836 316,636

Property, Plant And Equipment (

Property, Plant And Equipment (Tables)	12 Months Ended
	Dec. 31, 2016
Property, Plant and Equipment [Abstract]
Schedule Of Property, Plant And Equipment	NiSource’s property, plant and equipment on the Consolidated Balance Sheets are classified as follows: At December 31, (in millions) 2016 2015 Property Plant and Equipment Gas Distribution Utility (1) $ 11,556.6 $ 10,620.4 Electric Utility (1)(2) 7,043.3 7,765.7 Corporate 105.0 107.2 Construction Work in Process 663.1 453.6 Non-Utility and Other (2) 681.7 41.2 Total Property, Plant and Equipment $ 20,049.7 $ 18,988.1 Accumulated Depreciation and Amortization Gas Distribution Utility (1) $ (3,119.2 ) $ (3,029.0 ) Electric Utility (1)(2) (3,442.0 ) (3,767.7 ) Corporate (52.5 ) (56.7 ) Non-Utility and Other (2) (368.0 ) (23.2 ) Total Accumulated Depreciation and Amortization $ (6,981.7 ) $ (6,876.6 ) Net Property, Plant and Equipment $ 13,068.0 $ 12,111.5 (1) NIPSCO’s common utility plant and associated accumulated depreciation and amortization are allocated between Gas Distribution Utility and Electric Utility Property, Plant and Equipment. (2) Non-Utility and Other in 2016 primarily consists of Bailly Generating Station (Units 7 and 8) which were reclassified from Electric Utility in the fourth quarter of 2016. Depreciation expense for the remaining net book value will continue to be recorded at the composite depreciation rate most recently approved by the IURC. See Note 18-E, "Other Matters," for additional information.
Schedule Of Depreciation Provisions For Utility Plant As A Percentage Of The Original Cost	The weighted average depreciation provisions for utility plant, as a percentage of the original cost, for the periods ended December 31, 2016 , 2015 and 2014 were as follows: 2016 2015 2014 Electric Operations 3.3 % 3.1 % 3.0 % Gas Distribution Operations 2.1 % 2.0 % 2.1 %

Goodwill and Other Intangible40

Goodwill and Other Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2016
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Goodwill	The following presents NiSource's goodwill balance allocated by segment as of December 31, 2016 : (in millions) Gas Distribution Operations Electric Operations Corporate and Other Total Goodwill $ 1,690.7 $ — $ — $ 1,690.7

Asset Retirement Obligations (T

Asset Retirement Obligations (Tables)	12 Months Ended
	Dec. 31, 2016
Asset Retirement Obligation [Abstract]
Changes In Liability For Asset Retirement Obligations	Changes in NiSource’s liability for asset retirement obligations for the years 2016 and 2015 are presented in the table below: (in millions) 2016 2015 Beginning Balance $ 254.0 $ 136.2 Accretion recorded as a regulatory asset/liability 9.2 8.6 Additions — 6.5 Settlements (7.5 ) (7.0 ) Change in estimated cash flows 6.9 (1) 109.7 (2) Ending Balance $ 262.6 $ 254.0 (1) The change in estimated cash flows for 2016 is primarily attributed to the changes in estimated costs for retirement of gas mains partially offset by revisions to estimated costs associated with the EPA's final rule for regulation of CCRs and changes to cost estimates for certain solid waste management units. See Note 18-D, "Environmental Matters," for additional information on CCRs. (2) The change in estimated cash flows for 2015 primarily represents estimated costs associated with the EPA's final rule for regulation of CCRs and changes to cost estimates for certain solid waste management units. See Note 18-D, "Environmental Matters," for additional information on CCRs.

Regulatory Matters (Tables)

Regulatory Matters (Tables)	12 Months Ended
	Dec. 31, 2016
Regulatory Assets and Liabilities Disclosure [Abstract]
Regulatory Assets	Regulatory assets were comprised of the following items: At December 31, (in millions) 2016 2015 Regulatory Assets Unrecognized pension benefit and other postretirement benefit costs (see Note 11) $ 847.5 $ 928.7 Other postretirement costs (see Note 11) 59.6 47.0 Environmental costs (see Note 18-D) 62.6 62.2 Regulatory effects of accounting for income taxes (see Note 1-O and Note 10) 238.4 234.1 Underrecovered gas and fuel costs (see Note 1-K) 73.5 34.8 Depreciation 136.8 124.5 Uncollectible accounts receivable deferred for future recovery 7.3 17.0 Post-in-service carrying charges 134.9 107.2 EERM operation and maintenance and depreciation deferral 54.1 48.1 Sugar Creek carrying charges and deferred depreciation 16.8 28.2 TDSIC 15.9 6.7 Safety Activity Costs 41.5 19.6 DSM Program 48.4 35.6 Other 148.1 113.0 Total Regulatory Assets $ 1,885.4 $ 1,806.7
Regulatory Liabilities	Regulatory liabilities were comprised of the following items: At December 31, (in millions) 2016 2015 Regulatory Liabilities Overrecovered gas and fuel costs (see Note 1-K) $ 54.8 $ 148.1 Cost of removal (see Note 7) 1,174.5 1,261.5 Regulatory effects of accounting for income taxes (see Note 1-O and Note 10) 30.0 34.2 Other postretirement costs (see Note 11) 41.2 38.8 Other 81.3 99.2 Total Regulatory Liabilities $ 1,381.8 $ 1,581.8

Risk Management Activities (Tab

Risk Management Activities (Tables)	12 Months Ended
	Dec. 31, 2016
Risk Management Activities [Abstract]
Schedule of Derivative Instruments in Statement of Financial Position, Fair Value	Risk management assets and liabilities on NiSource’s derivatives are presented on the Consolidated Balance Sheets as shown below: (in millions) 2016 2015 Risk Management Assets - Current (1) Interest rate risk programs $ 17.0 $ — Commodity price risk programs 7.4 0.1 Total $ 24.4 $ 0.1 Risk Management Assets - Noncurrent (2) Interest rate risk programs $ 17.1 $ — Commodity price risk programs 7.5 — Total $ 24.6 $ — Risk Management Liabilities - Current (3) Interest rate risk programs $ 15.3 $ — Commodity price risk programs 1.5 9.3 Total $ 16.8 $ 9.3 Risk Management Liabilities - Noncurrent Interest rate risk programs $ 24.5 $ 17.4 Commodity price risk programs 20.0 5.2 Total $ 44.5 $ 22.6 (1) Presented in "Prepayments and other" on the Consolidated Balance Sheets. (2) Presented in "Deferred charges and other" on the Consolidated Balance Sheets. (3) Presented in "Other accruals" on the Consolidated Balance Sheets.

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Schedule Of Components Of Income Tax Expense	The components of income tax expense (benefit) were as follows: Year Ended December 31, (in millions) 2016 2015 2014 Income Taxes Current Federal $ — $ — $ — State (0.1 ) 6.0 5.4 Total Current (0.1 ) 6.0 5.4 Deferred Federal 165.6 124.1 129.5 State 18.0 13.6 35.4 Total Deferred 183.6 137.7 164.9 Deferred Investment Credits (1.4 ) (2.4 ) (3.5 ) Income Taxes from Continuing Operations $ 182.1 $ 141.3 $ 166.8
Schedule Of Reasons Behind Differences In Computation Of Total Income Taxes	Total income taxes from continuing operations were different from the amount that would be computed by applying the statutory federal income tax rate to book income before income tax. The major reasons for this difference were as follows: Year Ended December 31, (in millions) 2016 2015 2014 Book income from Continuing Operations before income taxes $ 510.2 $ 339.9 $ 423.0 Tax expense at statutory Federal income tax rate 178.6 35.0 % 118.9 35.0 % 148.1 35.0 % Increases (reductions) in taxes resulting from: State income taxes, net of Federal income tax benefit 11.3 2.2 14.8 4.4 15.7 3.7 Regulatory treatment of depreciation differences 2.1 0.4 4.3 1.3 0.7 0.2 Amortization of deferred investment tax credits (1.4 ) (0.3 ) (2.4 ) (0.7 ) (3.5 ) (0.8 ) Nondeductible expenses 1.9 0.4 2.1 0.6 0.8 0.2 Employee stock ownership plan dividends (2.3 ) (0.5 ) (2.9 ) (0.9 ) (3.8 ) (0.9 ) AFUDC equity (2.2 ) (0.4 ) (3.5 ) (1.0 ) (3.5 ) (0.8 ) Charitable contribution carryforward adjustment 2.8 0.5 17.8 5.2 — — Federal tax benefits on stock compensation (7.2 ) (1.4 ) — — — — Tax accrual adjustments and other, net (1.5 ) (0.2 ) (7.8 ) (2.3 ) 12.3 2.8 Income Taxes from Continuing Operations $ 182.1 35.7 % $ 141.3 41.6 % $ 166.8 39.4 %
Schedule Of Principal Components Of Net Deferred Tax Liability	Deferred income taxes result from temporary differences between the financial statement carrying amounts and the tax basis of existing assets and liabilities. The principal components of NiSource’s net deferred tax liability were as follows: At December 31, (in millions) 2016 2015 Deferred tax liabilities Accelerated depreciation and other property-related differences $ 3,825.7 $ 3,510.8 Unrecovered gas and fuel costs 25.9 11.2 Other regulatory assets 449.2 403.3 Premiums and discounts associated with long-term debt 1.5 9.9 Total Deferred Tax Liabilities 4,302.3 3,935.2 Deferred tax assets Other regulatory liabilities (93.1 ) (74.4 ) Cost of removal (502.2 ) (519.4 ) Pension and other postretirement/postemployment benefits (261.7 ) (243.8 ) Environmental liabilities (47.0 ) (45.9 ) Net operating loss carryforward and Alternative Minimum Tax credit carryforward (646.2 ) (437.4 ) Other accrued liabilities (45.5 ) (89.0 ) Other, net (178.6 ) (160.0 ) Total Deferred Tax Assets (1,774.3 ) (1,569.9 ) Net Deferred Tax Liabilities $ 2,528.0 $ 2,365.3
Schedule Of Reconciliation Of The Beginning And Ending Amounts Of Unrecognized Tax Benefits	A reconciliation of the beginning and ending amounts of unrecognized tax benefits is as follows: Reconciliation of Unrecognized Tax Benefits (in millions) 2016 2015 2014 Unrecognized Tax Benefits - Opening Balance $ 0.9 $ 24.4 $ 23.7 Gross increases - tax positions in prior period 2.6 0.4 — Gross decreases - tax positions in prior period (0.9 ) (23.9 ) (1.0 ) Gross increases - current period tax positions — — 1.7 Unrecognized Tax Benefits - Ending Balance $ 2.6 $ 0.9 $ 24.4 Offset for net operating loss carryforwards — (0.9 ) (24.2 ) Balance - Less Net Operating Loss Carryforwards $ 2.6 $ — $ 0.2

Pension And Other Postretirem45

Pension And Other Postretirement Benefits (Tables)	12 Months Ended
	Dec. 31, 2016
Pension and Other Postretirement Benefit Expense [Abstract]
Schedule Of Allocation of Plan Assets	Asset Mix Policy of Funds: Defined Benefit Pension Plan Postretirement Benefit Plan Asset Category Minimum Maximum Minimum Maximum Domestic Equities 25% 45% 35% 55% International Equities 15% 25% 15% 25% Fixed Income 23% 37% 20% 50% Real Estate/Private Equity/Hedge Funds 0% 15% 0% 0% Short-Term Investments 0% 10% 0% 10% Pension Plan and Postretirement Plan Asset Mix at December 31, 2016 and December 31, 2015 : (in millions) Defined Benefit Pension Assets December 31, Postretirement December 31, Asset Class Asset Value % of Total Assets Asset Value % of Total Assets Domestic Equities $ 755.2 43.1 % $ 97.9 42.3 % International Equities 339.9 19.4 % 41.8 18.0 % Fixed Income 565.8 32.3 % 87.0 37.6 % Real Estate/Private Equity/Hedge Funds 74.8 4.3 % — — Cash/Other 15.2 0.9 % 4.7 2.1 % Total $ 1,750.9 100.0 % $ 231.4 100.0 % (in millions) Defined Benefit Pension Assets December 31, Postretirement Benefit Plan Assets December 31, Asset Class Asset Value % of Total Assets Asset Value % of Total Assets Domestic Equities $ 686.3 39.3 % $ 105.0 46.5 % International Equities 323.2 18.5 % 39.6 17.5 % Fixed Income 619.3 35.5 % 79.1 35.0 % Real Estate/Private Equity/Hedge Funds 96.7 5.5 % — — Cash/Other 21.6 1.2 % 2.2 1.0 % Total $ 1,747.1 100.0 % $ 225.9 100.0 %
Schedule Of Fair Value and Changes In The Fair Value Of The Plan Assets	Fair Value Measurements at December 31, 2016 : (in millions) December 31, Quoted Prices in Active Significant Other Significant Pension plan assets: Cash $ 1.9 $ 1.9 $ — $ — Fixed income securities Government 42.2 — 42.2 — Corporate 104.1 — 104.1 — Other fixed income 0.1 — — 0.1 Mutual Funds U.S. multi-strategy 283.2 283.2 — — International equities 116.6 116.6 — — Fixed income 135.6 135.6 — — Private equity limited partnerships U.S. multi-strategy (1) 34.8 — — 34.8 International multi-strategy (2) 24.9 — — 24.9 Distressed opportunities 4.1 — — 4.1 Real estate 9.2 — — 9.2 Commingled funds Short-term money markets (3) 16.6 U.S. equities (3) 472.0 International equities (3) 223.2 Fixed income (3) 280.7 Pension plan assets subtotal 1,749.2 537.3 146.3 73.1 Other postretirement benefit plan assets: Mutual funds U.S. equities 85.4 85.4 — — International equities 41.8 41.8 — — Fixed income 86.8 86.8 — — Commingled funds Short-term money markets (3) 9.5 U.S. equities (3) 12.5 Other postretirement benefit plan assets subtotal 236.0 214.0 — — Due to brokers, net (4) (5.0 ) Receivables/payables 2.1 Total pension and other postretirement benefit plan assets $ 1,982.3 $ 751.3 $ 146.3 $ 73.1 (1) This class includes limited partnerships/fund of funds that invest in a diverse portfolio of private equity strategies, including buy-outs, venture capital, growth capital, special situations and secondary markets, primarily inside the United States. (2) This class includes limited partnerships/fund of funds that invest in diverse portfolio of private equity strategies, including buy-outs, venture capital, growth capital, special situations and secondary markets, primarily outside the United States. (3) This class of investments is measured at fair value using the net asset value per share and has not been classified in the fair value hierarchy. (4) This class represents pending trades with brokers. The table below sets forth a summary of changes in the fair value of the Plan’s Level 3 assets for the year ended December 31, 2016 : Balance at January 1, 2016 Total gains or losses (unrealized / realized) Purchases (Sales) Transfers into/(out of) level 3 Balance at December 31, 2016 Fixed income securities Other fixed income $ 0.1 $ — $ — $ — $ — $ 0.1 Private equity limited partnerships U.S. multi-strategy 46.4 2.1 0.8 (14.5 ) — 34.8 International multi-strategy 29.3 2.0 1.0 (7.4 ) — 24.9 Distressed opportunities 5.9 (0.4 ) 0.1 (1.5 ) — 4.1 Real estate 13.6 0.1 0.1 (4.6 ) — 9.2 Total $ 95.3 $ 3.8 $ 2.0 $ (28.0 ) $ — $ 73.1 The table below sets forth a summary of unfunded commitments, redemption frequency and redemption notice periods for certain investments that are measured at fair value using the net asset value per share for the year ended December 31, 2016 : (in millions) Fair Value Unfunded Commitments Redemption Frequency Redemption Notice Period Commingled Funds Short-term money markets $ 26.1 $ — Daily 1 day U.S. equities 484.5 — Monthly 3 days International equities 223.2 — Monthly 14-30 days Fixed income 280.7 — Monthly 3 days Total $ 1,014.5 $ — Fair Value Measurements at December 31, 2015 : (in millions) December 31, Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Significant Pension plan assets: Cash $ 7.0 $ 7.0 $ — $ — Equity securities International equities 45.3 45.3 — — Fixed income securities Government 64.6 — 64.6 — Corporate 95.8 — 95.8 — Other fixed income 0.1 — — 0.1 Mutual Funds U.S. multi-strategy 257.1 257.1 — — International equities 64.9 64.9 — — Fixed income 150.5 150.5 — — Private equity limited partnerships U.S. multi-strategy (1) 46.4 — — 46.4 International multi-strategy (2) 29.3 — — 29.3 Distressed opportunities 5.9 — — 5.9 Real Estate 13.6 — — 13.6 Commingled funds Short-term money markets (3) 22.9 U.S. equities (3) 429.2 International equities (3) 210.1 Fixed income (3) 302.5 Pension plan assets subtotal 1,745.2 524.8 160.4 95.3 Other postretirement benefit plan assets: Mutual funds U.S. equities 89.8 89.8 — — International equities 41.4 41.4 — — Fixed income 78.0 78.0 — — Commingled funds Short-term money markets (3) 2.4 U.S. equities (3) 14.3 Other postretirement benefit plan assets subtotal 225.9 209.2 — — Due to brokers, net (4) (0.2 ) Receivables/payables 2.1 Total pension and other postretirement benefit plan assets $ 1,973.0 $ 734.0 $ 160.4 $ 95.3 (1) This class includes limited partnerships/fund of funds that invest in a diverse portfolio of private equity strategies, including buy-outs, venture capital, growth capital, special situations and secondary markets, primarily in the United States. (2) This class includes limited partnerships/fund of funds that invest in a diverse portfolio of private equity strategies, including buy-outs, venture capital, growth capital, special situations and secondary markets, primarily outside the United States. (3) This class of investments is measured at fair value using the net asset value per share and has not been classified in the fair value hierarchy. (4) This class represents pending trades with brokers. The table below sets forth a summary of changes in the fair value of the Plan’s Level 3 assets for the year ended December 31, 2015 : Balance at January 1, 2015 Total gains or losses (unrealized / realized) Purchases (Sales) Transfers into/(out of) level 3 Balance at December 31, 2015 Fixed income securities Other fixed income $ 0.6 $ — $ — $ (0.5 ) $ — $ 0.1 Private equity limited partnerships U.S. multi-strategy 56.2 (3.5 ) 1.1 (7.4 ) — 46.4 International multi-strategy 35.3 (2.3 ) 0.1 (3.8 ) — 29.3 Distress opportunities 7.6 (0.5 ) — (1.2 ) — 5.9 Real estate 17.3 (0.5 ) 0.1 (3.3 ) — 13.6 Total $ 117.0 $ (6.8 ) $ 1.3 $ (16.2 ) $ — $ 95.3 The table below sets forth a summary of unfunded commitments, redemption frequency and redemption notice periods for certain investments that are measured at fair value using the net asset value per share for the year ended December 31, 2015 : (in millions) Fair Value Unfunded Commitments Redemption Frequency Redemption Notice Period Commingled Funds Short-term money markets $ 25.3 $ — Daily 1 day U.S. equities 443.5 — Monthly 3 days International equities 210.1 — Monthly 14-30 days Fixed income 302.5 — Monthly 3 days Total $ 981.4 $ —
Schedule Of Reconciliation Of The Plan Funded Status	The following table provides a reconciliation of the plans’ funded status and amounts reflected in NiSource’s Consolidated Balance Sheets at December 31 based on a December 31 measurement date: Pension Benefits Other Postretirement Benefits (in millions) 2016 2015 2016 2015 Change in projected benefit obligation (1) Benefit obligation at beginning of year $ 2,206.7 $ 2,751.4 $ 525.8 $ 716.0 Service cost 30.7 34.8 5.0 6.4 Interest cost 89.7 95.9 22.0 24.9 Plan participants’ contributions — — 5.9 7.3 Plan amendments — — 7.5 0.1 Actuarial loss (gain) (2.7 ) (91.7 ) 1.0 (71.5 ) Settlement loss — 0.5 — — Benefits paid (158.6 ) (171.8 ) (38.9 ) (43.7 ) Estimated benefits paid by incurred subsidy — — 0.7 0.8 Separation of CPG (Note 3) — (412.4 ) — (114.5 ) Projected benefit obligation at end of year $ 2,165.8 $ 2,206.7 $ 529.0 $ 525.8 Change in plan assets Fair value of plan assets at beginning of year $ 1,747.1 $ 2,330.3 $ 225.9 $ 465.0 Actual return on plan assets 159.1 (49.7 ) 13.0 1.9 Employer contributions 3.3 2.7 25.5 25.8 Plan participants’ contributions — — 5.9 7.3 Benefits paid (158.6 ) (171.8 ) (38.9 ) (43.7 ) Separation of CPG (Note 3) — (364.4 ) — (230.4 ) Fair value of plan assets at end of year $ 1,750.9 $ 1,747.1 $ 231.4 $ 225.9 Funded Status at end of year $ (414.9 ) $ (459.6 ) $ (297.6 ) $ (299.9 ) Amounts recognized in the statement of financial position consist of: Current liabilities (2.9 ) (3.0 ) (0.7 ) (0.6 ) Noncurrent liabilities (412.0 ) (456.6 ) (296.9 ) (299.3 ) Net amount recognized at end of year (2) $ (414.9 ) $ (459.6 ) $ (297.6 ) $ (299.9 ) Amounts recognized in accumulated other comprehensive income or regulatory asset/liability (3) Unrecognized prior service credit $ 1.0 $ 0.7 $ (29.2 ) $ (41.6 ) Unrecognized actuarial loss 835.5 925.6 68.3 66.1 Net amount recognized at end of year $ 836.5 $ 926.3 $ 39.1 $ 24.5 (1) The change in benefit obligation for Pension Benefits represents the change in Projected Benefit Obligation while the change in benefit obligation for Other Postretirement Benefits represents the change in Accumulated Postretirement Benefit Obligation. (2) NiSource recognizes in its Consolidated Balance Sheets the underfunded and overfunded status of its various defined benefit postretirement plans, measured as the difference between the fair value of the plan assets and the benefit obligation. (3) NiSource determined that for certain rate-regulated subsidiaries the future recovery of pension and other postretirement benefits costs is probable. These rate-regulated subsidiaries recorded regulatory assets and liabilities of $847.5 million and $0.3 million , respectively, as of December 31, 2016 , and $928.7 million and $8.1 million , respectively, as of December 31, 2015 that would otherwise have been recorded to accumulated other comprehensive loss.
Schedule Of Significant Actuarial Assumptions In Determining Funded Status Plan	The following table provides the key assumptions that were used to calculate the pension and other postretirement benefits obligations for NiSource’s various plans as of December 31: Pension Benefits Other Postretirement Benefits 2016 2015 2016 2015 Weighted-average assumptions to Determine Benefit Obligation Discount Rate 4.03 % 4.24 % 4.12 % 4.33 % Rate of Compensation Increases 4.00 % 4.00 % — — Health Care Trend Rates Trend for Next Year — — 8.43 % 8.41 % Ultimate Trend — — 4.50 % 4.50 % Year Ultimate Trend Reached — — 2024 2022
Schedule Of One-Percentage-Point Change In Assumed Health Care Cost Trend Rates	Assumed health care cost trend rates have a significant effect on the amounts reported for the health care plans. A one-percentage-point change in assumed health care cost trend rates would have the following effects: (in millions) 1% point increase 1% point decrease Effect on service and interest components of net periodic cost $ 1.3 $ (1.1 ) Effect on accumulated postretirement benefit obligation 27.2 (23.8 )
Schedule Of Expected Payments To Participants In Pension Plan	The expected benefits are estimated based on the same assumptions used to measure NiSource’s benefit obligation at the end of the year and includes benefits attributable to the estimated future service of employees: (in millions) Pension Benefits Other Federal Year(s) 2017 $ 171.9 $ 34.1 $ 0.7 2018 172.5 34.9 0.7 2019 171.1 35.8 0.7 2020 171.2 36.5 0.7 2021 172.2 37.2 0.7 2022-2026 816.8 180.9 2.9
Components Of The Plans' Net Periodic Benefits Cost	The following table provides the components of the plans’ net periodic benefits cost for each of the three years ended December 31, 2016 , 2015 and 2014 : Pension Benefits Other Postretirement Benefits (in millions) 2016 2015 2014 2016 2015 2014 Components of Net Periodic Benefit Cost (Income) Service cost $ 30.7 $ 34.8 $ 34.8 $ 5.0 $ 6.4 $ 8.5 Interest cost 89.7 95.9 109.0 22.0 24.9 30.1 Expected return on assets (132.9 ) (167.2 ) (181.1 ) (17.2 ) (28.2 ) (36.8 ) Amortization of prior service cost (credit) (0.2 ) 0.1 0.2 (4.9 ) (5.2 ) (4.3 ) Recognized actuarial loss 61.2 59.3 47.5 3.1 3.4 0.4 Net Periodic Benefit Costs (Income) 48.5 22.9 10.4 8.0 1.3 (2.1 ) Additional loss recognized due to: Settlement loss — 2.5 — — — — Total Net Periodic Benefits Cost (Income) $ 48.5 $ 25.4 $ 10.4 $ 8.0 $ 1.3 $ (2.1 )
Schedule Of Key Assumptions That Were Used To Calculate The Net Periodic Benefits Cost	The following table provides the key assumptions that were used to calculate the net periodic benefits cost for NiSource’s various plans: Pension Benefits Other Postretirement Benefits 2016 2015 2014 2016 2015 2014 Weighted-average Assumptions to Determine Net Periodic Benefit Cost Discount Rate 4.24 % 3.81 % 4.50 % 4.33 % 3.94 % 4.75 % Expected Long-Term Rate of Return on Plan Assets 8.00 % 8.30 % 8.30 % 7.85 % 8.15 % 8.14 % Rate of Compensation Increases 4.00 % 4.00 % 4.00 % — — —
Schedule Of Changes In Plan Assets And Projected Benefit Obligations Recognized In Other Comprehensive Income	The following table provides other changes in plan assets and projected benefit obligations recognized in other comprehensive income or regulatory asset or liability: Pension Benefits Other Postretirement Benefits (in millions) 2016 2015 2016 2015 Other Changes in Plan Assets and Projected Benefit Obligations Recognized in Other Comprehensive Income or Regulatory Asset or Liability Net prior service cost $ — $ — $ 7.5 $ 0.1 Net actuarial loss (gain) (28.9 ) 125.7 5.3 (45.2 ) Settlements — (2.5 ) — — Less: amortization of prior service cost (credit) 0.2 (0.1 ) 4.9 5.2 Less: amortization of net actuarial gain (61.2 ) (59.3 ) (3.1 ) (3.4 ) Less: Separation of CPG (Note 3) — (143.8 ) — 21.5 Total Recognized in Other Comprehensive Income or Regulatory Asset or Liability $ (89.9 ) $ (80.0 ) $ 14.6 $ (21.8 ) Amount Recognized in Net Periodic Benefits Cost and Other Comprehensive Income or Regulatory Asset or Liability $ (41.4 ) $ (54.6 ) $ 22.6 $ (20.5 )

Share-Based Compensation (Table

Share-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2016
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Schedule Of Transactions Of Share Based Compensation Other Than Stock Options	(shares) Restricted Stock Units Weighted Average Grant Date Fair Value Per Unit ($) Nonvested at December 31, 2015 3,142,473 8.55 Granted 65,418 21.49 Forfeited (46,447 ) 11.71 Vested (1,519,414 ) 5.21 Nonvested at December 31, 2016 1,642,030 12.05
Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Schedule Of Transactions Of Share Based Compensation Other Than Stock Options	(shares) Performance Awards Weighted Average Grant Date Fair Value Per Unit ($) Nonvested at December 31, 2015 — — Granted 647,305 19.50 Forfeited — — Vested — — Nonvested at December 31, 2016 647,305 19.50

Long-Term Debt (Tables)

Long-Term Debt (Tables)	12 Months Ended
	Dec. 31, 2016
Long-term Debt, Current and Noncurrent [Abstract]
Schedule of Long-Term Debt	NiSource long-term debt as of December 31, 2016 and 2015 is as follows: Long-term debt type Maturity Weighted average interest rate (%) Outstanding balance as of December 31, (in millions) 2016 2015 Senior notes: NiSource Finance March 2016 10.75 % $ — $ 201.5 NiSource Finance November 2016 5.41 % — 90.0 NiSource Finance September 2017 5.25 % 210.4 210.4 NiSource Finance March 2018 6.40 % 476.0 476.0 NiSource Finance January 2019 6.80 % 500.0 500.0 NiSource Finance March 2019 Variable (1) 500.0 — NiSource Finance September 2020 5.45 % 550.0 550.0 NiSource Finance December 2021 4.45 % 63.6 63.6 NiSource Finance March 2022 6.13 % 500.0 500.0 NiSource Finance February 2023 3.85 % 250.0 250.0 NiSource Finance November 2025 5.89 % 265.0 265.0 NiSource Finance December 2040 6.25 % 250.0 250.0 NiSource Finance June 2041 5.95 % 400.0 400.0 NiSource Finance February 2042 5.80 % 250.0 250.0 NiSource Finance February 2043 5.25 % 500.0 500.0 NiSource Finance February 2044 4.80 % 750.0 750.0 NiSource Finance February 2045 5.65 % 500.0 500.0 Capital Markets December 2027 6.78 % 3.0 3.0 Total senior notes $ 5,968.0 $ 5,759.5 Medium term notes: Columbia of Massachusetts December 2025 to February 2028 6.30 % $ 40.0 $ 40.0 Capital Markets March 2017 to May 2027 7.92 % 106.0 106.0 NIPSCO June 2017 to August 2027 7.57 % 95.5 95.5 Total medium term notes $ 241.5 $ 241.5 Capital leases: NiSource Corporate Services October 2019 to April 2021 2.92 % $ 3.5 $ 3.7 NIPSCO May 2018 3.95 % 12.7 52.8 Columbia of Ohio October 2021 to June 2038 6.53 % 80.1 79.8 Columbia of Massachusetts December 2033 to July 2036 5.33 % 23.7 24.1 Columbia of Virginia August 2024 to July 2029 12.27 % 5.5 5.8 Columbia of Pennsylvania August 2027 to June 2036 5.45 % 31.9 32.4 Total capital leases 157.4 198.6 Pollution control bonds - NIPSCO July 2017 to April 2019 5.76 % 96.0 226.0 Notes payable - NiSource Development Company July 2041 5.56 % — 2.1 Unamortized issuance costs and discounts (41.6 ) $ (45.5 ) Total Long-Term Debt 6,421.3 $ 6,382.2 (1) Rate of one month Libor plus 95 basis points.

Short-Term Borrowings (Tables)

Short-Term Borrowings (Tables)	12 Months Ended
	Dec. 31, 2016
Short-term Debt [Abstract]
Schedule Of Short-Term Borrowings	Short-term borrowings were as follows: At December 31, (in millions) 2016 2015 Commercial Paper weighted average interest rate of 1.24 % and 1.00% at December 31, 2016 and 2015, respectively. $ 1,178.0 $ 321.4 Accounts receivable securitization facility borrowings 310.0 246.0 Total Short-Term Borrowings $ 1,488.0 $ 567.4

Fair Value (Tables)

Fair Value (Tables)	12 Months Ended
	Dec. 31, 2016
Fair Value Disclosures [Abstract]
Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis	The following tables present financial assets and liabilities measured and recorded at fair value on NiSource’s Consolidated Balance Sheets on a recurring basis and their level within the fair value hierarchy as of December 31, 2016 and December 31, 2015 : Recurring Fair Value Measurements December 31, 2016 ( in millions ) Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Balance as of December 31, 2016 Assets Risk management assets $ 5.4 $ 43.6 $ — $ 49.0 Available-for-sale securities — 131.5 — 131.5 Total $ 5.4 $ 175.1 $ — $ 180.5 Liabilities Risk management liabilities $ 1.2 $ 58.9 $ 1.2 $ 61.3 Total $ 1.2 $ 58.9 $ 1.2 $ 61.3 Recurring Fair Value Measurements December 31, 2015 ( in millions ) Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Balance as of December 31, 2015 Assets Risk management assets $ 0.1 $ — $ — $ 0.1 Available-for-sale securities — 128.7 — 128.7 Total $ 0.1 $ 128.7 $ — $ 128.8 Liabilities Risk management liabilities $ 14.3 $ 17.4 $ 0.2 $ 31.9 Total $ 14.3 $ 17.4 $ 0.2 $ 31.9
Available-For-Sale Debt Securities	The amortized cost, gross unrealized gains and losses and fair value of available-for-sale securities at December 31, 2016 and 2015 were: December 31, 2016 (in millions) Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Available-for-sale securities U.S. Treasury debt securities $ 35.0 $ 0.1 $ (0.6 ) $ 34.5 Corporate/Other debt securities 98.7 0.3 (2.0 ) 97.0 Total $ 133.7 $ 0.4 $ (2.6 ) $ 131.5 December 31, 2015 (in millions) Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Available-for-sale securities U.S. Treasury debt securities $ 33.7 $ 0.1 $ (0.3 ) $ 33.5 Corporate/Other debt securities 95.7 0.3 (0.8 ) 95.2 Total $ 129.4 $ 0.4 $ (1.1 ) $ 128.7
Carrying Amount And Estimated Fair Values Of Financial Instruments	The carrying amount and estimated fair values of financial instruments were as follows: At December 31, (in millions) Carrying Amount 2016 Estimated Fair Value 2016 Carrying Amount 2015 Estimated Fair Value 2015 Long-term debt (including current portion) $ 6,421.3 $ 7,064.1 $ 6,382.2 $ 6,975.7

Transfers Of Financial Assets (

Transfers Of Financial Assets (Tables)	12 Months Ended
	Dec. 31, 2016
Transfers and Servicing [Abstract]
Schedule of Assets and Associated Liabilities Accounted for as Secured Borrowings	The following table reflects the gross and net receivables transferred as well as short-term borrowings related to the securitization transactions as of December 31, 2016 and 2015 for Columbia of Ohio, NIPSCO and Columbia of Pennsylvania: (in millions) December 31, December 31, Gross Receivables $ 618.3 $ 450.8 Less: Receivables not transferred 308.3 204.8 Net receivables transferred $ 310.0 $ 246.0 Short-term debt due to asset securitization $ 310.0 $ 246.0

Other Commitments And Conting51

Other Commitments And Contingencies (Tables)	12 Months Ended
	Dec. 31, 2016
Commitments and Contingencies Disclosure [Abstract]
Contractual Obligation, Fiscal Year Maturity Schedule [Table Text Block]	Contractual Obligations . NiSource has certain contractual obligations requiring payments at specified periods. The obligations include long-term debt, lease obligations, energy commodity contracts and obligations for various services including pipeline capacity and IBM outsourcing. The total contractual obligations in existence at December 31, 2016 and their maturities were: (in millions) Total 2017 2018 2019 2020 2021 After Long-term debt (1) $ 6,305.5 $ 349.9 $ 476.0 $ 1,041.0 $ 550.0 $ 63.6 $ 3,825.0 Capital leases (2) 250.0 22.7 18.5 14.2 13.5 13.4 167.7 Interest payments on long-term debt 4,611.2 337.9 305.3 265.2 244.9 214.9 3,243.0 Operating leases (3) 54.6 15.4 9.4 7.5 4.8 4.1 13.4 Energy commodity contracts (4) 312.1 108.5 67.7 67.3 68.0 0.6 — Service obligations: Pipeline service obligations 2,002.1 532.7 382.7 293.1 176.0 139.2 478.4 IBM service obligations 325.0 84.1 81.2 80.0 79.7 — — Other service obligations 77.7 58.1 17.4 1.9 0.3 — — Other liabilities 34.4 34.4 — — — — — Total contractual obligations $ 13,972.6 $ 1,543.7 $ 1,358.2 $ 1,770.2 $ 1,137.2 $ 435.8 $ 7,727.5 (1) Long-term debt balance excludes unamortized issuance costs and discounts of $41.6 million. (2) Capital lease payments shown above are inclusive of interest totaling $92.6 million. (3) Operating lease balances do not include amounts for fleet leases that can be renewed beyond the initial lease term. The Company anticipates renewing the leases beyond the initial term, but the anticipated payments associated with the renewals do not meet the definition of expected minimum lease payments and therefore are not included above. Expected payments are $31.1 million in 2017, $32.9 million in 2018, $26.1 million in 2019, $17.5 million in 2020, $8.0 million in 2021 and $2.0 million thereafter. (4) In January 2017, NIPSCO signed new coal contract commitments of $24.2 million and $10.1 million for 2017 and 2018, respectively. These contracts are not included above.

Accumulated Other Comprehensi52

Accumulated Other Comprehensive Loss (Tables)	12 Months Ended
	Dec. 31, 2016
Components of Accumulated Other Comprehensive Income (Loss) [Abstract]
Schedule of Accumulated Other Comprehensive Income (Loss)	The following table displays the activity of Accumulated Other Comprehensive Loss, net of tax: (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 (loss) before reclassifications 0.9 (0.3 ) (10.2 ) (9.6 ) Amounts reclassified from accumulated other comprehensive loss (0.3 ) 2.5 0.4 2.6 Net current-period other comprehensive income (loss) 0.6 2.2 (9.8 ) (7.0 ) Balance as of December 31, 2014 $ 0.3 $ (23.6 ) $ (27.3 ) $ (50.6 ) Other comprehensive loss before reclassifications (0.5 ) (11.0 ) (5.0 ) (16.5 ) Amounts reclassified from accumulated other comprehensive loss (0.3 ) 3.2 2.6 5.5 Net current-period other comprehensive loss (0.8 ) (7.8 ) (2.4 ) (11.0 ) Allocation of AOCI to noncontrolling interest — 2.0 — 2.0 Distribution of CPG to shareholders (Refer to Note 3, "Discontinued Operations") — 13.9 10.6 24.5 Balance as of December 31, 2015 $ (0.5 ) $ (15.5 ) $ (19.1 ) $ (35.1 ) Other comprehensive income before reclassifications — 7.1 0.5 7.6 Amounts reclassified from accumulated other comprehensive loss (0.1 ) 1.5 1.0 2.4 Net current-period other comprehensive income (loss) (0.1 ) 8.6 1.5 10.0 Balance as of December 31, 2016 $ (0.6 ) $ (6.9 ) $ (17.6 ) $ (25.1 ) (1) All amounts are net of tax. Amounts in parentheses indicate debits.

Other, Net (Tables)

Other, Net (Tables)	12 Months Ended
	Dec. 31, 2016
Other Nonoperating Income (Expense) [Abstract]
Schedule Of Other, Net	Year Ended December 31, (in millions) 2016 2015 2014 Interest Income $ 3.4 $ 0.8 $ 3.8 AFUDC Equity 11.6 11.5 10.7 Charitable Contributions (4.5 ) (4.8 ) (11.1 ) Miscellaneous (1) (9.0 ) 9.9 10.0 Total Other, net $ 1.5 $ 17.4 $ 13.4 (1) Miscellaneous in 2016 primarily consists of a TUA-related charge of $8.6 million to reflect the estimated amount owed to the upgrade sponsors for the portion of the multiplier previously collected for taxes. Refer to Note 18-E, "Other Matters," for additional information. In 2015 and 2014, Miscellaneous primarily consisted of TUA income.

Interest Expense, Net (Tables)

Interest Expense, Net (Tables)	12 Months Ended
	Dec. 31, 2016
Interest Expense [Abstract]
Schedule Of Interest Expense, Net	Year Ended December 31, (in millions) 2016 2015 2014 Interest on long-term debt $ 352.3 $ 377.5 $ 368.6 Interest on short-term borrowings 9.2 2.2 5.2 Debt discount/cost amortization 7.6 8.7 8.0 Accounts receivable securitization fees 2.3 2.5 2.9 Allowance for borrowed funds used and interest capitalized during construction (5.6 ) (5.4 ) (5.3 ) Other (1) (16.3 ) (5.3 ) 0.1 Total Interest Expense, net $ 349.5 $ 380.2 $ 379.5 (1) The change in Other for 2016 is primarily attributed to increases in Columbia of Ohio's post-in-service carrying charges (PISCC).

Segments Of Business (Tables)

Segments Of Business (Tables)	12 Months Ended
	Dec. 31, 2016
Segment Reporting [Abstract]
Schedule Of Operating Income Derived From Revenues And Expenses By Segment	Year Ended December 31, (in millions) 2016 2015 2014 Gross Revenues Gas Distribution Operations Unaffiliated $ 2,818.2 $ 3,068.7 $ 3,593.6 Intersegment 12.4 0.4 0.3 Total 2,830.6 3,069.1 3,593.9 Electric Operations Unaffiliated 1,660.8 1,573.6 1,672.6 Intersegment 0.8 0.8 0.8 Total 1,661.6 1,574.4 1,673.4 Corporate and Other Unaffiliated 13.5 9.5 6.2 Intersegment 413.3 396.4 412.5 Total 426.8 405.9 418.7 Eliminations (426.5 ) (397.6 ) (413.6 ) Consolidated Gross Revenues $ 4,492.5 $ 4,651.8 $ 5,272.4 Year Ended December 31, (in millions) 2016 2015 2014 Operating Income (Loss) Gas Distribution Operations $ 574.0 $ 555.8 $ 537.0 Electric Operations 291.4 264.4 282.7 Corporate and Other (7.2 ) (20.3 ) (30.6 ) Consolidated Operating Income $ 858.2 $ 799.9 $ 789.1 Depreciation and Amortization Gas Distribution Operations $ 252.9 $ 232.6 $ 217.6 Electric Operations 274.5 267.7 244.4 Corporate and Other 19.7 24.1 24.9 Consolidated Depreciation and Amortization $ 547.1 $ 524.4 $ 486.9 Assets Gas Distribution Operations $ 11,096.4 $ 10,094.5 $ 9,443.7 Electric Operations 5,233.3 5,265.3 5,009.9 Corporate and Other (1) 2,362.2 2,132.7 10,136.2 Consolidated Assets $ 18,691.9 $ 17,492.5 $ 24,589.8 Capital Expenditures (2) Gas Distribution Operations $ 1,054.4 $ 917.0 $ 860.3 Electric Operations 420.6 400.3 438.8 Corporate and Other 15.4 50.2 40.5 Consolidated Capital Expenditures $ 1,490.4 $ 1,367.5 $ 1,339.6 (1) Corporate and Other in 2014 includes assets of Discontinued Operations. Refer to Note 3, "Discontinued Operations," for additional information. (2) Amounts differ from those presented on the Statements of Consolidated Cash Flows primarily due to the inclusion of capital expenditures included in current liabilities and AFUDC Equity.

Quarterly Financial Data (Table

Quarterly Financial Data (Tables)	12 Months Ended
	Dec. 31, 2016
Quarterly Financial Data [Abstract]
Schedule Of Quarterly Financial Data	(in millions, except per share data) First Quarter (1) Second Quarter (1) Third Quarter Fourth Quarter 2016 Gross revenues $ 1,436.6 $ 897.6 $ 861.3 $ 1,297.0 Operating Income 381.4 138.2 113.7 224.9 Income from Continuing Operations 186.6 29.0 23.7 88.8 Results from Discontinued Operations - net of taxes — (0.1 ) 3.5 — Net Income 186.6 28.9 27.2 88.8 Basic Earnings Per Share Continuing Operations 0.58 0.09 0.07 0.28 Discontinued Operations — — 0.01 — Basic Earnings Per Share $ 0.58 $ 0.09 $ 0.08 $ 0.28 Diluted Earnings Per Share Continuing Operations 0.58 0.09 0.07 0.27 Discontinued Operations — — 0.01 — Diluted Earnings Per Share $ 0.58 $ 0.09 $ 0.08 $ 0.27 2015 Gross revenues $ 1,852.2 $ 884.6 $ 817.2 $ 1,097.8 Operating Income 386.3 84.4 109.7 219.5 Income (Loss) from Continuing Operations 192.5 (73.1 ) 14.8 64.4 Results from Discontinued Operations - net of taxes (2) 82.8 45.4 (19.7 ) (5.0 ) Net Income (Loss) 275.3 (27.7 ) (4.9 ) 59.4 Net Income (Loss) attributable to NiSource 268.4 (36.4 ) (4.9 ) 59.4 Basic Earnings (Loss) Per Share Continuing Operations 0.61 (0.23 ) 0.05 0.20 Discontinued Operations 0.24 0.12 (0.07 ) (0.01 ) Basic Earnings (Loss) Per Share $ 0.85 $ (0.11 ) $ (0.02 ) $ 0.19 Diluted Earnings (Loss) Per Share Continuing Operations 0.61 (0.23 ) 0.05 0.20 Discontinued Operations 0.24 0.12 (0.07 ) (0.01 ) Diluted Earnings (Loss) Per Share $ 0.85 $ (0.11 ) $ (0.02 ) $ 0.19 (1) First and second quarter results for 2016 differ from the results presented in the as-filed Form 10-Q for the respective periods as a result of the adoption of ASU 2016-09 in the third quarter of 2016 . Refer to Note 2, "Recent Accounting Pronouncements," for additional information. (2) Includes the results of the former Columbia Pipeline Group segment.

Supplemental Cash Flow Inform57

Supplemental Cash Flow Information (Tables)	12 Months Ended
	Dec. 31, 2016
Supplemental Cash Flow Information [Abstract]
Schedule of Cash Flow, Supplemental Disclosures	The following tables provide additional information regarding NiSource’s Consolidated Statements of Cash Flows for the years ended December 31, 2016 , 2015 and 2014 : Year Ended December 31, (in millions) 2016 2015 2014 Supplemental Disclosures of Cash Flow Information Non-cash transactions: Capital expenditures included in current liabilities $ 125.3 $ 121.6 $ 127.4 Assets acquired under a capital lease 4.0 47.5 76.7 Schedule of interest and income taxes paid: Cash paid for interest, net of interest capitalized amounts $ 337.8 $ 390.4 $ 429.3 Cash paid for income taxes 8.0 21.3 19.4

Valuation and Qualifying Acco58

Valuation and Qualifying Accounts (Tables)	12 Months Ended
	Dec. 31, 2016
Valuation and Qualifying Accounts [Abstract]
Schedule of Valuation and Qualifying Accounts Disclosure	NISOURCE INC. SCHEDULE II – VALUATION AND QUALIFYING ACCOUNTS Twelve months ended December 31, 2016 Additions ($ in millions) Balance Jan. 1, 2016 Charged to Costs and Expenses Charged to Other Account (1) Deductions for Purposes for which Reserves were Created Balance Dec. 31, 2016 Reserves Deducted in Consolidated Balance Sheet from Assets to Which They Apply: Reserve for accounts receivable $ 20.3 $ 19.7 $ 48.5 $ 65.2 $ 23.3 Reserve for other investments 3.0 — — — 3.0 Twelve months ended December 31, 2015 Additions ($ in millions) Balance Charged to Costs and Expenses Charged to Other Account (1) Deductions for Purposes for which Reserves were Created Balance Reserves Deducted in Consolidated Balance Sheet from Assets to Which They Apply: Reserve for accounts receivable $ 24.9 $ 22.5 $ 56.7 $ 83.8 $ 20.3 Reserve for other investments 3.0 — — — 3.0 Twelve months ended December 31, 2014 Additions ($ in millions) Balance Charged to Costs and Expenses Charged to Other Account (1) Deductions for Purposes for which Reserves were Created Balance Reserves Deducted in Consolidated Balance Sheet from Assets to Which They Apply: Reserve for accounts receivable $ 23.4 $ 21.8 $ 69.9 $ 90.2 $ 24.9 Reserve for other investments 3.0 — — — 3.0 (1) Charged to Other Accounts reflects the deferral of bad debt expense to a regulatory asset.

Nature Of Operations And Summ59

Nature Of Operations And Summary Of Significant Accounting Policies (Narrative) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2016USD ($)shares	Dec. 31, 2015USD ($)shares	Dec. 31, 2014USD ($)shares
Basis Of Accounting Presentation [Line Items]
Number of customers	3,900,000
Unbilled revenue, less reserves	$ 329.7	$ 237.1
Other than Temporary Impairment Losses, Investments	$ 0	$ 0	$ 0
Pre-tax rate for allowance for funds used during construction	4.50%	4.70%	4.50%
Anti-dilutive shares | shares	0	0	0
Inventory valued using LIFO	$ 46.1	$ 50.2
Excess of replacement over LIFO value	(9.4)	(27.2)
Inventory valued using the weighted average cost methodology	233.8	293.3
NIPSCO
Basis Of Accounting Presentation [Line Items]
Weighted Average Electric Production Fuel Inventory	112.8	106.3
Weighted Average Materials and Supplies Inventory	$ 101.7	$ 86.8

Recent Accounting Pronounceme60

Recent Accounting Pronouncements (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Recent Accounting Pronouncements [Abstract]
Cumulative effect of change in accounting principle		$ 25.3
Excess Tax Benefit from Share-based Compensation, Operating Activities	$ 7.2

Discontinued Operations (Narrat

Discontinued Operations (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Jul. 01, 2015	May 22, 2015
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Assets	$ 18,691.9	$ 17,492.5	$ 24,589.8
Transaction Costs Related to Separation		55.4	23.7
Related Party Transaction, Other Revenues from Transactions with Related Party	150.5	147.6	$ 146.2
Tax benefit ffrom favorable estimate-to-actual adjustments	3.6
Columbia Pipeline Group Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Assets	0	0		$ 9,200
Liabilities	$ 0	$ 0		5,600
Equity				$ 3,600
Columbia Pipeline Group
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Debt Instrument, Face Amount					$ 2,750

Discontinued Operations (Income

Discontinued Operations (Income Statement Disclosures) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015		Dec. 31, 2014
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Transportation and storage revenues		$ 561.4		$ 1,034.3
Other revenues		94.3		312.9
Total Sales Revenues		655.7		1,347.2
Less: Cost of sales (excluding depreciation and amortization)		0.2		0.3
Net Revenues		655.5		1,346.9
Operation and maintenance		375.8		769.1
Depreciation and amortization		66.4		118.6
Gain on sale of assets		(13.6)		(34.5)
Other taxes		38		67.1
Total Operating Expenses		466.6		920.3
Equity Earnings in Unconsolidated Affiliates		29.1		46.6
Operating Income from Discontinued Operations		218		473.2
Interest expense, net		(37.1)		(64.1)
Other, net		8.2		7.9
Total Other Income (Deductions)		(28.9)		(56.2)
Income from Discontinued Operations before Income Taxes		189.1		417
Income Taxes		85.6		143.2
Income (Loss) from Discontinued Operations - net of taxes	$ 3.4	103.5		273.8
Columbia Pipeline Group Operations | Discontinued Operations, Disposed of by Means Other than Sale, Spinoff [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Transportation and storage revenues		561.4		1,034.3
Other revenues		94.3		312.9
Total Sales Revenues		655.7		1,347.2
Less: Cost of sales (excluding depreciation and amortization)		0.2		0.3
Net Revenues		655.5		1,346.9
Operation and maintenance		375.8	[1]	769.1	[2]
Depreciation and amortization		66.4		118.6
Gain on sale of assets		(13.6)		(34.5)
Other taxes		38		67.1
Total Operating Expenses		466.6		920.3
Equity Earnings in Unconsolidated Affiliates		29.1		46.6
Operating Income from Discontinued Operations		218		473.2
Interest expense, net		(37.1)		(64.1)
Other, net		7.8		8.9
Total Other Income (Deductions)		(29.3)		(55.2)
Income from Discontinued Operations before Income Taxes		188.7		418
Income Taxes		84.7		143.5
Income (Loss) from Discontinued Operations - net of taxes		104		274.5
Corporate and Other | Discontinued Operations, Disposed of by Means Other than Sale, Spinoff [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Transportation and storage revenues		0		0
Other revenues		0		0
Total Sales Revenues		0		0
Less: Cost of sales (excluding depreciation and amortization)		0		0
Net Revenues		0		0
Operation and maintenance		0		0
Depreciation and amortization		0		0
Gain on sale of assets		0		0
Other taxes		0		0
Total Operating Expenses		0		0
Equity Earnings in Unconsolidated Affiliates		0		0
Operating Income from Discontinued Operations		0		0
Interest expense, net		0		0
Other, net		0.4		1
Total Other Income (Deductions)		0.4		(1)
Income from Discontinued Operations before Income Taxes		0.4		(1)
Income Taxes		0.9		(0.3)
Income (Loss) from Discontinued Operations - net of taxes		$ (0.5)		$ (0.7)
[1]	Includes approximately $55.4 million of transaction costs related to the Separation.
[2]	Includes approximately $23.7 million of transaction costs related to the Separation.

Earnings Per Share Earnings Per

Earnings Per Share Earnings Per Share (Details) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Earnings Per Share [Abstract]
Basic Average Common Shares Outstanding	321,805	317,746	315,120
Nonqualified stock options	0	0	6
Shares contingently issuable under employee stock plans	165	0	1,066
Shares restricted under stock plans	1,554	2,090	444
Weighted Average Number of Shares Outstanding, Diluted	323,524	319,836	316,636

Property, Plant And Equipment64

Property, Plant And Equipment (Schedule Of Property, Plant And Equipment) (Details) - USD ($) $ in Millions		Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Property Plant and Equipment		$ 20,049.7	$ 18,988.1
Accumulated Depreciation and Amortization		(6,981.7)	(6,876.6)
Net Property, Plant and Equipment		13,068	12,111.5
Gas Distribution Utility
Property, Plant and Equipment [Line Items]
Property Plant and Equipment	[1]	11,556.6	10,620.4
Accumulated Depreciation and Amortization	[1]	(3,119.2)	(3,029)
Electric Utility
Property, Plant and Equipment [Line Items]
Property Plant and Equipment	[1],[2]	7,043.3	7,765.7
Accumulated Depreciation and Amortization	[1],[2]	(3,442)	(3,767.7)
Common Utility
Property, Plant and Equipment [Line Items]
Property Plant and Equipment		105	107.2
Accumulated Depreciation and Amortization		(52.5)	(56.7)
Construction Work In Process
Property, Plant and Equipment [Line Items]
Property Plant and Equipment		663.1	453.6
Non-Utility And Other
Property, Plant and Equipment [Line Items]
Property Plant and Equipment	[2]	681.7	41.2
Accumulated Depreciation and Amortization	[2]	$ (368)	$ (23.2)
[1]	NIPSCO’s common utility plant and associated accumulated depreciation and amortization are allocated between Gas Distribution Utility and Electric Utility Property, Plant and Equipment.
[2]	Non-Utility and Other in 2016 primarily consists of Bailly Generating Station (Units 7 and 8) which were reclassified from Electric Utility in the fourth quarter of 2016. Depreciation expense for the remaining net book value will continue to be recorded at the composite depreciation rate most recently approved by the IURC. See Note 18-E, "Other Matters," for additional information.

Property, Plant And Equipment P

Property, Plant And Equipment Property, Plant and Equipment (Schedule of Depreciation Provisions For Utility Plant as a Percentage of the Original Cost) (Details)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Electric Operations
Property, Plant and Equipment [Line Items]
Depreciation Provisions For Utility Plant Percentage	3.30%	3.10%	3.00%
Gas Distribution Operations
Property, Plant and Equipment [Line Items]
Depreciation Provisions For Utility Plant Percentage	2.10%	2.00%	2.10%

Property, Plant and Equipment66

Property, Plant and Equipment (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Abstract]
Capitalized Computer Software, Amortization	$ 41.4	$ 41.1	$ 33.7
Capitalized Computer Software, Gross	$ 156.4	$ 167.1

Goodwill And Other Intangible67

Goodwill And Other Intangible Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Goodwill And Other Intangible Assets [Line Items]
Goodwill	$ 1,690.7	$ 1,690.7
Intangible assets excluding goodwill	242.7	253.7
Amortization	199.5	188.5
Amortization of Intangible Assets	$ 11	$ 11	$ 11
Finite-Lived Intangible Asset, Useful Life	40 years
Finite-Lived Intangible Assets, Amortization End Date	2,039
Gas Distribution Operations
Goodwill And Other Intangible Assets [Line Items]
Goodwill	$ 1,690.7
Electric Operations
Goodwill And Other Intangible Assets [Line Items]
Goodwill	0
Corporate and Other
Goodwill And Other Intangible Assets [Line Items]
Goodwill	$ 0

Asset Retirement Obligations (C

Asset Retirement Obligations (Changes In Company's Liability For Asset Retirement Obligations) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016		Dec. 31, 2015
Asset Retirement Obligation [Abstract]
Beginning Balance	$ 254		$ 136.2
Accretion recorded as a regulatory asset	9.2		8.6
Additions	0		6.5
Settlements	(7.5)		(7)
Change in estimated cash flows	6.9	[1]	109.7	[2]
Ending Balance	$ 262.6		$ 254
[1]	The change in estimated cash flows for 2016 is primarily attributed to the changes in estimated costs for retirement of gas mains partially offset by revisions to estimated costs associated with the EPA's final rule for regulation of CCRs and changes to cost estimates for certain solid waste management units. See Note 18-D, "Environmental Matters," for additional information on CCRs.
[2]	The change in estimated cash flows for 2015 primarily represents estimated costs associated with the EPA's final rule for regulation of CCRs and changes to cost estimates for certain solid waste management units. See Note 18-D, "Environmental Matters," for additional information on CCRs.

Regulatory Matters (Narrative)

Regulatory Matters (Narrative) (Details) - USD ($) $ in Millions

Jan. 17, 2017

Dec. 27, 2016

Dec. 22, 2016

Nov. 28, 2016

Oct. 31, 2016

Oct. 27, 2016

Oct. 20, 2016

Sep. 16, 2016

Aug. 26, 2016

Jul. 27, 2016

Jun. 30, 2016

May 27, 2016

Apr. 29, 2016

Apr. 15, 2016

Mar. 18, 2016

Mar. 16, 2016

Mar. 11, 2016

Feb. 26, 2016

Feb. 19, 2016

Oct. 30, 2015

Oct. 07, 2015

Oct. 01, 2015

Apr. 16, 2015

Dec. 17, 2014

Nov. 12, 2013

Jul. 19, 2013

Sep. 30, 2016

Sep. 30, 2016

Dec. 31, 2016

Dec. 31, 2015

Dec. 31, 2014

Dec. 31, 2016

Dec. 28, 2016

Oct. 26, 2016

Mar. 24, 2016

Regulatory Matters [Line Items]

Remaining Recovery Period of Regulatory Assets for which No Return on Investment During Recovery Period is Provided

41 years

Regulatory asset not earning return on investment

$ 1,708.2

$ 1,708.2

Expenses recovered as components of cost of service and regulatory orders

1,561.9

1,561.9

Regulatory assets Requiring Specific Rate Action

323.5

323.5

Increase (Decrease) in Regulatory Assets and Liabilities

187.9

$ (82)

$ 227.7

Seven Year Plan of Eligible Investments, Length of Plan

seven-year

Columbia Of Ohio

Regulatory Matters [Line Items]

Public Utilities, Requested Rate Increase (Decrease), Amount

$ 33.5

$ 25.9

Requested Regulatory Deferral

$ 25

Approved Regulatory Deferral

$ 25

$ 15

Depreciation Before Rate Regulation

78.2

638

Decrease In Depreciation And Amortization Over That Reflected In Rates

7.7

74.1

Depreciation And Amortization Reflected In Rates

85.9

712.1

Depreciation Regulatory Asset

57.6

65.3

57.6

Requested IRP Extension

5 years

Columbia Of Pennsylvania

Regulatory Matters [Line Items]

Public Utilities, Requested Rate Increase (Decrease), Amount

$ 55.3

Capital Investment Program Amount

232

Capital Investment Program Amount year 2

$ 267

Public Utilities, Approved Rate Increase (Decrease), Amount

$ 35

Columbia Of Virginia

Regulatory Matters [Line Items]

Public Utilities, Requested Rate Increase (Decrease), Amount

$ 37

Columbia Of Kentucky

Regulatory Matters [Line Items]

Public Utilities, Requested Rate Increase (Decrease), Amount

$ 13.1

$ 25.4

Public Utilities, Approved Rate Increase (Decrease), Amount

$ 13.4

NIPSCO

Regulatory Matters [Line Items]

Public Utilities, Requested Rate Increase (Decrease), Amount

$ 45.5

Amount of public utility's requested rate increase (decrease) with regulatory agency, before riders

$ 72.5

$ 126.6

Increase (Decrease) in Regulatory Assets and Liabilities

$ 7.8

New Seven Year Plan of Eligible Investments under TDSIC

$ 1,300

New Seven year Plan of Eligible Investments Under TDSIC, Amount of Investment, Updated

$ 1,250

Public Utilities, Approved Return on Equity, Percentage

12.38%

Public utilities, Approved Return on Equity, Percentage, Amended

9.70%

10.82%

10.32%

Liability associated with Public Utilities, requested amendment to ROE

$ 6.5

6.5

Columbia Of Massachusetts

Regulatory Matters [Line Items]

Public Utilities, Requested Rate Increase (Decrease), Amount

$ 49

Public Utilities, Approved Rate Increase (Decrease), Amount

$ 32.8

Projected Peak Undercollection

$ 3.6

Columbia Of Maryland

Regulatory Matters [Line Items]

Public Utilities, Requested Rate Increase (Decrease), Amount

$ 6.5

Public Utilities, Requested Rate Increase (Decrease), Amended, Amount

$ 3.7

IRP | Columbia Of Ohio

Regulatory Matters [Line Items]

Deferred Depreciation

23.4

23.4

Capital Expenditure Program | Columbia Of Ohio

Regulatory Matters [Line Items]

Deferred Depreciation

31.8

31.8

TDSIC 5 Gas | NIPSCO

Regulatory Matters [Line Items]

Seven Year Plan of Eligible Investments Under TDSIC

$ 824

Regulatory Net Capital Expenditures Included In Filing

$ 211.6

2016 GSEP | Columbia Of Massachusetts

Regulatory Matters [Line Items]

Public Utilities, Requested Rate Increase (Decrease), Amount

$ 6.4

Public Utilities, Requested Rate Increase (Decrease), Cumulative Amount

$ 9

Public Utilities, Requested Rate Increase (Decrease), Revised Cumulative Amount

$ 8.2

2017 GSEP | Columbia Of Massachusetts

Regulatory Matters [Line Items]

Public Utilities, Approved Rate Increase (Decrease), Amount

$ 8.1

CMA Off-peak RDAF | Columbia Of Massachusetts

Regulatory Matters [Line Items]

Public Utilities, Requested Rate Increase (Decrease), Amount

$ 12.9

$ 3.4

Public Utilities, Approved Rate Increase (Decrease), Amount

8.9

ECR 28 | NIPSCO

Regulatory Matters [Line Items]

Regulatory Net Capital Expenditures Included In Filing

$ 267

2017 GSEP | Columbia Of Massachusetts

Regulatory Matters [Line Items]

Public Utilities, Requested Rate Increase (Decrease), Cumulative Amount

$ 16.8

CMA Peak Period RDAF | Columbia Of Massachusetts

Regulatory Matters [Line Items]

Public Utilities, Requested Rate Increase (Decrease), Amount

$ 4

ECR 27 | NIPSCO

Regulatory Matters [Line Items]

Regulatory Net Capital Expenditures Included In Filing

$ 261.1

$ 261.1

Subsequent Event | Columbia Of Virginia

Regulatory Matters [Line Items]

Public Utilities, Requested Rate Increase (Decrease), Amount

$ 28.5

Regulatory Matters (Regulatory

Regulatory Matters (Regulatory Assets) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Regulatory Assets [Line Items]
Total Assets	$ 1,885.4	$ 1,806.7
Unrecognized Pension Benefit And Other Postretirement Benefit Costs
Regulatory Assets [Line Items]
Total Assets	847.5	928.7
Other Postretirement Costs
Regulatory Assets [Line Items]
Total Assets	59.6	47
Environmental Costs
Regulatory Assets [Line Items]
Total Assets	62.6	62.2
Regulatory Effects Of Accounting For Income Taxes
Regulatory Assets [Line Items]
Total Assets	238.4	234.1
Underrecovered Gas And Fuel Costs
Regulatory Assets [Line Items]
Total Assets	73.5	34.8
Depreciation
Regulatory Assets [Line Items]
Total Assets	136.8	124.5
Uncollectible Accounts Receivable Deferred For Future Recovery
Regulatory Assets [Line Items]
Total Assets	7.3	17
Post-In Service Carrying Charges
Regulatory Assets [Line Items]
Total Assets	134.9	107.2
EERM Operation And Maintenance And Depreciation Deferral
Regulatory Assets [Line Items]
Total Assets	54.1	48.1
Sugar Creek Carrying Charges And Deferred Depreciation
Regulatory Assets [Line Items]
Total Assets	16.8	28.2
TDSIC
Regulatory Assets [Line Items]
Total Assets	15.9	6.7
Safety Activity Costs
Regulatory Assets [Line Items]
Total Assets	41.5	19.6
DSM Program
Regulatory Assets [Line Items]
Total Assets	48.4	35.6
Other Assets
Regulatory Assets [Line Items]
Total Assets	$ 148.1	$ 113

Regulatory Matters (Regulator71

Regulatory Matters (Regulatory Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Regulatory Liabilities [Line Items]
Regulatory Liabilities	$ 1,381.8	$ 1,581.8
Overrecovered Gas And Fuel Costs
Regulatory Liabilities [Line Items]
Regulatory Liabilities	54.8	148.1
Cost Of Removal
Regulatory Liabilities [Line Items]
Regulatory Liabilities	1,174.5	1,261.5
Regulatory Effects Of Accounting For Income Taxes
Regulatory Liabilities [Line Items]
Regulatory Liabilities	30	34.2
Other Postretirement Costs
Regulatory Liabilities [Line Items]
Regulatory Liabilities	41.2	38.8
Other Liabilities
Regulatory Liabilities [Line Items]
Regulatory Liabilities	$ 81.3	$ 99.2

Risk Management Activities (Nar

Risk Management Activities (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Jun. 24, 2016
Risk Management Activities [Abstract]
Notional Amount of Forward-Starting Interest rate Swap Agreements	$ 1,500	$ 1,000		$ 500
Swap Forecasted Debt Issuance	2,018
Gain (Loss) on Cash Flow Hedge Ineffectiveness, Net	$ 0	0	$ 0
Derivative Instruments, Gain (Loss) Recognized in Income, Ineffective Portion and Amount Excluded from Effectiveness Testing, Net	$ 0	$ 0	$ 0

Risk Management Activities (Sch

Risk Management Activities (Schedule of Derivative Instruments in Statement of Financial Position, Fair Value) (Details) - USD ($) $ in Millions		Dec. 31, 2016	Dec. 31, 2015
Derivatives, Fair Value [Line Items]
Derivative Asset		$ 49	$ 0.1
Derivative Liability		61.3	31.9
Risk Management Assets Current
Derivatives, Fair Value [Line Items]
Derivative Asset		24.4	0.1
Risk Management Assets Noncurrent
Derivatives, Fair Value [Line Items]
Derivative Asset		24.6	0
Risk Management Liabilities Current
Derivatives, Fair Value [Line Items]
Derivative Liability		16.8	9.3
Risk Management Liabilities Noncurrent
Derivatives, Fair Value [Line Items]
Derivative Liability		44.5	22.6
Interest rate risk programs | Risk Management Assets Current
Derivatives, Fair Value [Line Items]
Derivative Asset	[1]	17	0
Interest rate risk programs | Risk Management Assets Noncurrent
Derivatives, Fair Value [Line Items]
Derivative Asset	[2]	17.1	0
Interest rate risk programs | Risk Management Liabilities Current
Derivatives, Fair Value [Line Items]
Derivative Liability	[3]	15.3	0
Interest rate risk programs | Risk Management Liabilities Noncurrent
Derivatives, Fair Value [Line Items]
Derivative Liability		24.5	17.4
Commodity price risk programs | Risk Management Assets Current
Derivatives, Fair Value [Line Items]
Derivative Asset	[1]	7.4	0.1
Commodity price risk programs | Risk Management Assets Noncurrent
Derivatives, Fair Value [Line Items]
Derivative Asset	[2]	7.5	0
Commodity price risk programs | Risk Management Liabilities Current
Derivatives, Fair Value [Line Items]
Derivative Liability	[3]	1.5	9.3
Commodity price risk programs | Risk Management Liabilities Noncurrent
Derivatives, Fair Value [Line Items]
Derivative Liability		$ 20	$ 5.2
[1]	Presented in "Prepayments and other" on the Consolidated Balance Sheets.
[2]	Presented in "Deferred charges and other" on the Consolidated Balance Sheets.
[3]	Presented in "Other accruals" on the Consolidated Balance Sheets.

Income Taxes (Narrative) (Detai

Income Taxes (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 25, 2014	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Taxes [Line Items]
Unrecognized Tax Benefits		$ 2.6	$ 0.9	$ 24.4	$ 23.7
Effective income tax rates		35.70%	41.60%	39.40%
Increase (Decrease) in Effective Tax Rate		(5.90%)	2.20%
Expected benefits to be realized		$ 43.6	$ 34.7
Tax Expense Recognized Due to Rate Change				$ 7.1
Change In Unrecorded Tax Benefits		1.7
NOL Carryforwards Recognized From Remeasurement		2
Amortization Of Excess Tax Benefits		0.7	1.4	4.1
Unrecognized tax benefits, if recognized, would affect effective tax rate		1.7	0.9	4.1
Unrecognized Tax Benefits Resulting in Net Operating Loss Carryforward		$ 2.6	$ 0	$ 0.2
Income Tax Rate Change Period			6 years
Tax Credit Carryforward, Expiration Date		Dec. 31, 2030
Operating Loss Carryforwards, Valuation Allowance		$ 600.9
Deferred Tax Assets, Tax Credit Carryforwards, Alternative Minimum Tax		1.7
Unrecognized Tax Benefits, Income Tax Penalties Accrued		0
Federal tax on excess stock compensation [Domain]
Income Taxes [Line Items]
Change in tax expense		7.2
Write Down of Charitable Contributions [Domain]
Income Taxes [Line Items]
Change in tax expense		15	$ 17.8
Unamortized tax benefits		12
State Apportionment Changes and Permanent Items as a Result of Remeasurement [Domain]
Income Taxes [Line Items]
Change in tax expense			$ 10.5
PATH and 50% Bonus Depreciation [Domain]
Income Taxes [Line Items]
Change in tax expense		$ 5.8
Minimum
Income Taxes [Line Items]
Tax Credit Carryforward, Expiration Date		Dec. 31, 2028
Maximum
Income Taxes [Line Items]
Tax Credit Carryforward, Expiration Date		Dec. 31, 2036
Previous
Income Taxes [Line Items]
Corporate Income Tax Rate	6.50%
Current
Income Taxes [Line Items]
Corporate Income Tax Rate	4.90%

Income Taxes (Schedule Of Compo

Income Taxes (Schedule Of Components Of Income Tax Expense) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Schedule of Income Tax Expense/Benefit [Line Items]
Current federal income taxes	$ 0	$ 0	$ 0
Current state income taxes	(0.1)	6	5.4
Total current income taxes	(0.1)	6	5.4
Deferred federal income taxes	165.6	124.1	129.5
Deferred state income taxes	18	13.6	35.4
Total deferred income taxes	183.6	137.7	164.9
Deferred Investment Credits	(1.4)	(2.4)	(3.5)
Income Taxes from Continuing Operations	$ 182.1	$ 141.3	$ 166.8

Income Taxes (Schedule Of Reaso

Income Taxes (Schedule Of Reasons Behind Differences In Computation Of Total Income Taxes) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Schedule of Reasons Behind Differences in Computation of Total Income Taxes [Line Items]
Book income from Continuing Operations before income taxes	$ 510.2	$ 339.9	$ 423
Tax expense at statutory federal income tax rate, value	$ 178.6	$ 118.9	$ 148.1
Tax expense at statutory federal income tax rate, rate	35.00%	35.00%	35.00%
State income taxes, net of federal income tax benefit, value	$ 11.3	$ 14.8	$ 15.7
State income taxes, net of federal income tax benefit, rate	2.20%	4.40%	3.70%
Regulatory treatment of depreciation differences, value	$ 2.1	$ 4.3	$ 0.7
Regulatory treatment of depreciation differences, rate	0.40%	1.30%	0.20%
Amortization of deferred investment tax credits, value	$ (1.4)	$ (2.4)	$ (3.5)
Amortization of deferred investment tax credits, rate	(0.30%)	(0.70%)	(0.80%)
Nondeductible expenses, value	$ 1.9	$ 2.1	$ 0.8
Nondeductible expenses, rate	0.40%	0.60%	0.20%
Employee Stock Ownership Plan Dividends, value	$ (2.3)	$ (2.9)	$ (3.8)
Employee Stock Ownership Plan Dividends, rate	(0.50%)	(0.90%)	(0.90%)
Regulatory treatment of AFUDC-Equity, value	$ (2.2)	$ (3.5)	$ (3.5)
Regulatory treatment of AFUDC-Equity, rate	(0.40%)	(1.00%)	(0.80%)
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Charitable Contributions, Amount	$ 2.8	$ 17.8	$ 0
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Charitable Contributions, Percent	0.50%	5.20%	0.00%
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Share-based Compensation Cost, Amount	$ (7.2)	$ 0	$ 0
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Share-based Compensation Cost, Percent	(1.40%)	(0.00%)	(0.00%)
Effective Income Tax Rate Reconciliation, Other Adjustments, Percent	(0.20%)	(2.30%)	2.80%
Tax accrual adjustments and other, net, value	$ (1.5)	$ (7.8)	$ 12.3
Income Taxes from Continuing Operations	$ 182.1	$ 141.3	$ 166.8
Income Taxes from Continuing Operations, rate	35.70%	41.60%	39.40%

Income Taxes (Schedule Of Princ

Income Taxes (Schedule Of Principal Components Of Net Deferred Tax Liability) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Schedule of Principal Components of Net Tax Expense [Line Items]
Accelerated depreciation and other property differences	$ 3,825.7	$ 3,510.8
Unrecovered gas and fuel costs	25.9	11.2
Other regulatory assets	449.2	403.3
Premiums and discounts associated with long-term debt	1.5	9.9
Total Deferred Tax Liabilities	4,302.3	3,935.2
Deferred investment tax credits and other regulatory liabilities	(93.1)	(74.4)
Cost of removal	(502.2)	(519.4)
Pension and other postretirement/postemployment benefits	(261.7)	(243.8)
Environmental liabilities	(47)	(45.9)
Net operating loss carryforward	(646.2)	(437.4)
Other accrued liabilities	(45.5)	(89)
Other, net	(178.6)	(160)
Total Deferred Tax Assets	(1,774.3)	(1,569.9)
Net Deferred Tax Liabilities less Deferred Tax Assets	$ 2,528	$ 2,365.3

Income Taxes (Schedule Of Recon

Income Taxes (Schedule Of Reconciliation Of The Beginning And Ending Amounts Of Unrecognized Tax Benefits) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Schedule Of Reconciliation Of The Beginning And Ending Amounts Of Unrecognized Tax Benefits [Line Items]
Unrecognized Tax Benefits-Opening Balance	$ 0.9	$ 24.4	$ 23.7
Gross increases-tax positions in prior period	2.6	0.4	0
Gross decreases-tax positions in prior period	(0.9)	(23.9)	(1)
Gross increases-current period tax positions	0	0	1.7
Unrecognized Tax Benefits-Ending Balance	2.6	0.9	24.4
Operating Loss Carryforwards	0	(0.9)	(24.2)
Balance-Net of Refunds and NOL Carryforwards	$ 2.6	$ 0	$ 0.2

Pension And Other Postretirem79

Pension And Other Postretirement Benefits (Narrative) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016		Dec. 31, 2015		Dec. 31, 2014	Jul. 01, 2015
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets			$ 1,982.3		$ 1,973
Regulatory assets			1,885.4		1,806.7
Regulatory Liabilities			$ 1,381.8		1,581.8
Expected return on plan assets			8.00%
Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets			$ 1,750.9		1,747.1		$ 2,330.3
Defined Benefit Plan, Actuarial Gain (Loss)			28.9		(125.7)
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)			(0.2)		0.1		0.2
Defined Benefit Plan, Net Periodic Benefit Cost			48.5		25.4		$ 10.4
Employer contributions			3.3		2.7
Expected contribution			9.1
Accumulated benefit obligation			2,148.9		2,190.5
Funded status of plan			414.9		459.6
Pension and Other Postretirement Defined Benefit Plans, Liabilities	[1]		$ 414.9		$ 459.6
Expected return on plan assets			8.00%		8.30%		8.30%
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets			$ 231.4		$ 225.9		$ 465
Defined Benefit Plan, Actuarial Gain (Loss)			(5.3)		45.2
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)			(4.9)		(5.2)		(4.3)
Defined Benefit Plan, Net Periodic Benefit Cost			8		1.3		$ (2.1)
Employer contributions			25.5		25.8
Expected contribution			25.3
Funded status of plan			297.6		299.9
Pension and Other Postretirement Defined Benefit Plans, Liabilities	[1]		$ 297.6		$ 299.9
Expected return on plan assets			7.85%		8.15%		8.14%
Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets			$ 73.1		$ 95.3		$ 117
Percentage of investments			4.00%		5.00%
Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets					$ 0
Scenario, Forecast | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Actuarial Gain (Loss)		$ 53.6
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)		0.7
Amortization of transition obligation		0
Scenario, Forecast | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Actuarial Gain (Loss)		3
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)		4.4
Amortization of transition obligation		$ 0
Unrecognized Pension Benefit And Other Postretirement Benefit Costs
Defined Benefit Plan Disclosure [Line Items]
Regulatory assets			$ 847.5		928.7
Regulatory Liabilities			0.3		8.1
Columbia Pipeline Group | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Increase in funded status other postretirement benefit plans								$ 48
Columbia Pipeline Group | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Increase in funded status other postretirement benefit plans								$ 115.9
International Equities | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets			339.9		323.2
International Equities | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets			41.8		39.6
Commingled Funds | Short-Term Money Markets | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets			16.6	[2]	22.9	[3]
Commingled Funds | Short-Term Money Markets | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets			9.5	[2]	2.4	[3]
Commingled Funds | United States Equities | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets			472	[2]	429.2	[3]
Commingled Funds | United States Equities | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets			12.5	[2]	14.3	[3]
Commingled Funds | International Equities | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets			$ 223.2	[2]	$ 210.1	[3]
[1]	NiSource recognizes in its Consolidated Balance Sheets the underfunded and overfunded status of its various defined benefit postretirement plans, measured as the difference between the fair value of the plan assets and the benefit obligation.
[2]	This class of investments is measured at fair value using the net asset value per share and has not been classified in the fair value hierarchy.
[3]	This class of investments is measured at fair value using the net asset value per share and has not been classified in the fair value hierarchy.

Pension And Other Postretirem80

Pension And Other Postretirement Benefits (Schedule Of Portfolio Asset Mix) (Details)	12 Months Ended
	Dec. 31, 2016
Domestic Equities | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Equities, Minimum	25.00%
Equities, Maximum	45.00%
Domestic Equities | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Equities, Minimum	35.00%
Equities, Maximum	55.00%
International Equities | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Equities, Minimum	15.00%
Equities, Maximum	25.00%
International Equities | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Equities, Minimum	15.00%
Equities, Maximum	25.00%
Fixed Income | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Equities, Minimum	23.00%
Equities, Maximum	37.00%
Fixed Income | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Equities, Minimum	20.00%
Equities, Maximum	50.00%
Real Estate/Private Equity/Hedge Funds | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Equities, Minimum	0.00%
Equities, Maximum	15.00%
Real Estate/Private Equity/Hedge Funds | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Equities, Minimum	0.00%
Equities, Maximum	0.00%
Short-Term Investments | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Equities, Minimum	0.00%
Equities, Maximum	10.00%
Short-Term Investments | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Equities, Minimum	0.00%
Equities, Maximum	10.00%

Pension And Other Postretirem81

Pension And Other Postretirement Benefits (Schedule Of Pension Plan And Postretirement Plan Asset Mix) (Details) - USD ($) $ in Millions	Dec. 31, 2016		Dec. 31, 2015		Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	$ 1,982.3		$ 1,973
Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	$ 1,750.9		$ 1,747.1		$ 2,330.3
Percentage of total asset	100.00%		100.00%
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	$ 231.4		$ 225.9		$ 465
Percentage of total asset	100.00%		100.00%
Domestic Equities | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	$ 755.2		$ 686.3
Percentage of total asset	43.10%		39.30%
Domestic Equities | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	$ 97.9		$ 105
Percentage of total asset	42.30%		46.50%
International Equities | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	$ 339.9		$ 323.2
Percentage of total asset	19.40%		18.50%
International Equities | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	$ 41.8		$ 39.6
Percentage of total asset	18.00%		17.50%
Fixed Income | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	$ 565.8		$ 619.3
Percentage of total asset	32.30%		35.50%
Fixed Income | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	$ 87		$ 79.1
Percentage of total asset	37.60%		35.00%
Real Estate/Private Equity/Hedge Funds | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	$ 74.8		$ 96.7
Percentage of total asset	4.30%		5.50%
Real Estate/Private Equity/Hedge Funds | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	$ 0		$ 0
Percentage of total asset	0.00%		0.00%
Cash/Other [Member] | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	$ 15.2		$ 21.6
Percentage of total asset	0.90%		1.20%
Cash/Other [Member] | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	$ 4.7		$ 2.2
Percentage of total asset	2.10%		1.00%
Commingled Funds | Short-Term Money Markets | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	$ 16.6	[1]	$ 22.9	[2]
Commingled Funds | Short-Term Money Markets | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	9.5	[1]	2.4	[2]
Commingled Funds | International Equities | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	223.2	[1]	210.1	[2]
Commingled Funds | Fixed Income | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	280.7	[1]	302.5	[2]
Commingled Funds | United States Equities | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	472	[1]	429.2	[2]
Commingled Funds | United States Equities | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	$ 12.5	[1]	$ 14.3	[2]
[1]	This class of investments is measured at fair value using the net asset value per share and has not been classified in the fair value hierarchy.
[2]	This class of investments is measured at fair value using the net asset value per share and has not been classified in the fair value hierarchy.

Pension And Other Postretirem82

Pension And Other Postretirement Benefits (Schedule Of Fair Value Of Pension Plan Assets) (Details) - USD ($) $ in Millions	Dec. 31, 2016		Dec. 31, 2015		Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	$ 1,982.3		$ 1,973
Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	751.3		734
Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	146.3		160.4
Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	73.1		95.3		$ 117
Due To Brokers Net [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	(5)	[1]	(0.2)	[2]
Receivables/Payables [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	2.1		2.1
Fixed Income Securities [Member] | Other Fixed Income [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0.1		0.1		0.6
Private Equity Limited Partnerships [Member] | U.S. Multi-Strategy [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	34.8		46.4		56.2
Private Equity Limited Partnerships [Member] | International Multi-Strategy [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	24.9		29.3		35.3
Private Equity Limited Partnerships [Member] | Distressed Opportunities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	4.1		5.9		7.6
Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	1,750.9		1,747.1		2,330.3
Defined Benefit Plan Fair Value Of Plan Assets Before Pending Items	1,749.2		1,745.2
Pension Plan | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets Before Pending Items	537.3		524.8
Pension Plan | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets Before Pending Items	146.3		160.4
Pension Plan | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets Before Pending Items	73.1		95.3
Pension Plan | Cash [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	1.9		7
Pension Plan | Cash [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	1.9		7
Pension Plan | Cash [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0		0
Pension Plan | Cash [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0		0
Pension Plan | International Equities
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	339.9		323.2
Pension Plan | Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	565.8		619.3
Pension Plan | Equity Securities [Member] | International Equities
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets			45.3
Pension Plan | Equity Securities [Member] | International Equities | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets			45.3
Pension Plan | Equity Securities [Member] | International Equities | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets			0
Pension Plan | Equity Securities [Member] | International Equities | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets			0
Pension Plan | Fixed Income Securities [Member] | Government
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	42.2		64.6
Pension Plan | Fixed Income Securities [Member] | Government | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0		0
Pension Plan | Fixed Income Securities [Member] | Government | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	42.2		64.6
Pension Plan | Fixed Income Securities [Member] | Government | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0		0
Pension Plan | Fixed Income Securities [Member] | Corporate [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	104.1		95.8
Pension Plan | Fixed Income Securities [Member] | Corporate [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0		0
Pension Plan | Fixed Income Securities [Member] | Corporate [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	104.1		95.8
Pension Plan | Fixed Income Securities [Member] | Corporate [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0		0
Pension Plan | Fixed Income Securities [Member] | Other Fixed Income [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0.1		0.1
Pension Plan | Fixed Income Securities [Member] | Other Fixed Income [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0		0
Pension Plan | Fixed Income Securities [Member] | Other Fixed Income [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0		0
Pension Plan | Fixed Income Securities [Member] | Other Fixed Income [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0.1		0.1
Pension Plan | Commingled Funds | International Equities
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	223.2	[3]	210.1	[4]
Pension Plan | Commingled Funds | Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	280.7	[3]	302.5	[4]
Pension Plan | Commingled Funds | United States Equities
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	472	[3]	429.2	[4]
Pension Plan | Commingled Funds | Short-Term Money Markets
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	16.6	[3]	22.9	[4]
Pension Plan | Private Equity Limited Partnerships [Member] | U.S. Multi-Strategy [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	34.8	[5]	46.4	[6]
Pension Plan | Private Equity Limited Partnerships [Member] | U.S. Multi-Strategy [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	[5]	0	[6]
Pension Plan | Private Equity Limited Partnerships [Member] | U.S. Multi-Strategy [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	[5]	0	[6]
Pension Plan | Private Equity Limited Partnerships [Member] | U.S. Multi-Strategy [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	34.8	[5]	46.4	[6]
Pension Plan | Private Equity Limited Partnerships [Member] | International Multi-Strategy [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	24.9	[7]	29.3	[8]
Pension Plan | Private Equity Limited Partnerships [Member] | International Multi-Strategy [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	[7]	0	[8]
Pension Plan | Private Equity Limited Partnerships [Member] | International Multi-Strategy [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	[7]	0	[8]
Pension Plan | Private Equity Limited Partnerships [Member] | International Multi-Strategy [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	24.9	[7]	29.3	[8]
Pension Plan | Private Equity Limited Partnerships [Member] | Distressed Opportunities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	4.1		5.9
Pension Plan | Private Equity Limited Partnerships [Member] | Distressed Opportunities [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0		0
Pension Plan | Private Equity Limited Partnerships [Member] | Distressed Opportunities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0		0
Pension Plan | Private Equity Limited Partnerships [Member] | Distressed Opportunities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	4.1		5.9
Pension Plan | Real Estate [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	9.2		13.6
Pension Plan | Real Estate [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0		0
Pension Plan | Real Estate [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0		0
Pension Plan | Real Estate [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	9.2		13.6
Pension Plan | Mutual Funds [Member] | International Equities
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	116.6		64.9
Pension Plan | Mutual Funds [Member] | International Equities | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	116.6		64.9
Pension Plan | Mutual Funds [Member] | U.S. Multi-Strategy [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	283.2		257.1
Pension Plan | Mutual Funds [Member] | U.S. Multi-Strategy [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	283.2		257.1
Pension Plan | Mutual Funds [Member] | Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	135.6		150.5
Pension Plan | Mutual Funds [Member] | Fixed Income | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	135.6		150.5
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	231.4		225.9		$ 465
Defined Benefit Plan Fair Value Of Plan Assets Before Pending Items	236
Other Postretirement Benefits | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets			209.2
Defined Benefit Plan Fair Value Of Plan Assets Before Pending Items	214
Other Postretirement Benefits | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets			0
Defined Benefit Plan Fair Value Of Plan Assets Before Pending Items	0
Other Postretirement Benefits | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets			0
Defined Benefit Plan Fair Value Of Plan Assets Before Pending Items	0
Other Postretirement Benefits | International Equities
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	41.8		39.6
Other Postretirement Benefits | Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	87		79.1
Other Postretirement Benefits | Commingled Funds | United States Equities
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	12.5	[3]	14.3	[4]
Other Postretirement Benefits | Commingled Funds | Short-Term Money Markets
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	9.5	[3]	2.4	[4]
Other Postretirement Benefits | Mutual Funds [Member] | International Equities
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	41.8		41.4
Other Postretirement Benefits | Mutual Funds [Member] | International Equities | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	41.8		41.4
Other Postretirement Benefits | Mutual Funds [Member] | International Equities | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0		0
Other Postretirement Benefits | Mutual Funds [Member] | International Equities | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0		0
Other Postretirement Benefits | Mutual Funds [Member] | Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	86.8		78
Other Postretirement Benefits | Mutual Funds [Member] | Fixed Income | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	86.8		78
Other Postretirement Benefits | Mutual Funds [Member] | Fixed Income | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0		0
Other Postretirement Benefits | Mutual Funds [Member] | Fixed Income | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0		0
Other Postretirement Benefits | Mutual Funds [Member] | United States Equities
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	85.4		89.8
Other Postretirement Benefits | Mutual Funds [Member] | United States Equities | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	85.4		89.8
Other Postretirement Benefits | Mutual Funds [Member] | United States Equities | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0		0
Other Postretirement Benefits | Mutual Funds [Member] | United States Equities | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	$ 0		$ 0
[1]	This class represents pending trades with brokers.
[2]	This class represents pending trades with brokers.
[3]	This class of investments is measured at fair value using the net asset value per share and has not been classified in the fair value hierarchy.
[4]	This class of investments is measured at fair value using the net asset value per share and has not been classified in the fair value hierarchy.
[5]	This class includes limited partnerships/fund of funds that invest in a diverse portfolio of private equity strategies, including buy-outs, venture capital, growth capital, special situations and secondary markets, primarily inside the United States.
[6]	This class includes limited partnerships/fund of funds that invest in a diverse portfolio of private equity strategies, including buy-outs, venture capital, growth capital, special situations and secondary markets, primarily in the United States.
[7]	This class includes limited partnerships/fund of funds that invest in diverse portfolio of private equity strategies, including buy-outs, venture capital, growth capital, special situations and secondary markets, primarily outside the United States.
[8]	This class includes limited partnerships/fund of funds that invest in a diverse portfolio of private equity strategies, including buy-outs, venture capital, growth capital, special situations and secondary markets, primarily outside the United States.

Pension And Other Postretirem83

Pension And Other Postretirement Benefits (Schedule Of Changes In The Fair Value Of The Plan Level Three Assets) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at beginning of year	$ 1,973
Fair value of plan assets at end of year	1,982.3	$ 1,973
Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at beginning of year	95.3	117
Total gains or losses (unrealized / realized)	3.8	(6.8)
Purchases	2	1.3
(Sales)	(28)	(16.2)
Transfers into/(out of) level 3	0	0
Fair value of plan assets at end of year	73.1	95.3
Real Estate [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at beginning of year	13.6	17.3
Total gains or losses (unrealized / realized)	0.1	(0.5)
Purchases	0.1	0.1
(Sales)	(4.6)	(3.3)
Transfers into/(out of) level 3	0	0
Fair value of plan assets at end of year	9.2	13.6
Private Equity Limited Partnerships [Member] | U.S. Multi-Strategy [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at beginning of year	46.4	56.2
Total gains or losses (unrealized / realized)	2.1	(3.5)
Purchases	0.8	1.1
(Sales)	(14.5)	(7.4)
Transfers into/(out of) level 3	0	0
Fair value of plan assets at end of year	34.8	46.4
Private Equity Limited Partnerships [Member] | International Multi-Strategy [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at beginning of year	29.3	35.3
Total gains or losses (unrealized / realized)	2	(2.3)
Purchases	1	0.1
(Sales)	(7.4)	(3.8)
Transfers into/(out of) level 3	0	0
Fair value of plan assets at end of year	24.9	29.3
Private Equity Limited Partnerships [Member] | Distressed Opportunities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at beginning of year	5.9	7.6
Total gains or losses (unrealized / realized)	(0.4)	(0.5)
Purchases	0.1	0
(Sales)	(1.5)	(1.2)
Transfers into/(out of) level 3	0	0
Fair value of plan assets at end of year	4.1	5.9
Fixed Income Securities [Member] | Other Fixed Income [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at beginning of year	0.1	0.6
Total gains or losses (unrealized / realized)	0	0
Purchases	0	0
(Sales)	0	(0.5)
Transfers into/(out of) level 3	0	0
Fair value of plan assets at end of year	$ 0.1	$ 0.1

Pension And Other Postretirem84

Pension And Other Postretirement Benefits Pension and Other Postretirement Benefits (Schedule of Net Asset Value Per Share) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Net Asset Value Excluded From Fair Value By Input	$ 1,014.5	$ 981.4
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Unfunded Commitments	0	0
Commingled Funds | Short-Term Money Markets
Defined Benefit Plan Disclosure [Line Items]
Net Asset Value Excluded From Fair Value By Input	26.1	25.3
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Unfunded Commitments	$ 0	$ 0
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Investment Redemption, Frequency	Daily	Daily
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Investment Redemption, Notice Period	1 day	1 day
Commingled Funds | United States Equities
Defined Benefit Plan Disclosure [Line Items]
Net Asset Value Excluded From Fair Value By Input	$ 484.5	$ 443.5
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Unfunded Commitments	$ 0	$ 0
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Investment Redemption, Frequency	Monthly	Monthly
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Investment Redemption, Notice Period	3 days	3 days
Commingled Funds | International Equities
Defined Benefit Plan Disclosure [Line Items]
Net Asset Value Excluded From Fair Value By Input	$ 223.2	$ 210.1
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Unfunded Commitments	$ 0	$ 0
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Investment Redemption, Frequency	Monthly	Monthly
Commingled Funds | Fixed Income Funds
Defined Benefit Plan Disclosure [Line Items]
Net Asset Value Excluded From Fair Value By Input	$ 280.7	$ 302.5
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Unfunded Commitments	$ 0	$ 0
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Investment Redemption, Frequency	Monthly	Monthly
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Investment Redemption, Notice Period	3 days	3 days
Minimum | Commingled Funds | International Equities
Defined Benefit Plan Disclosure [Line Items]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Investment Redemption, Notice Period	14 days	14 days
Maximum | Commingled Funds | International Equities
Defined Benefit Plan Disclosure [Line Items]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Investment Redemption, Notice Period	30 days	30 days

Pension And Other Postretirem85

Pension And Other Postretirement Benefits (Schedule Of Reconciliation Of The Plans Funded Status And Amounts Reflected) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015		Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at beginning of year		$ 1,973
Fair value of plan assets at end of year		1,982.3	$ 1,973
Noncurrent liabilities		(296.9)	(299.3)
Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation at beginning of year	[1]	2,206.7	2,751.4
Service cost		30.7	34.8		$ 34.8
Interest cost		89.7	95.9		109
Plan participants' contributions		0	0
Plan amendments		0	0
Actuarial loss (gain)		(2.7)	(91.7)
Settlement Loss		0	0.5
Benefits paid		(158.6)	(171.8)
Estimated benefits paid by incurred subsidy		0	0
Projected Benefit Obligation Change Due to Separation		0	(412.4)
Plan Assets Change Due to Separation		0	(364.4)
Projected benefit obligation at end of year		2,165.8	2,206.7	[1]	2,751.4	[1]
Fair value of plan assets at beginning of year		1,747.1	2,330.3
Actual return on plan assets		159.1	(49.7)
Employer contributions		3.3	2.7
Fair value of plan assets at end of year		1,750.9	1,747.1		2,330.3
Funded Status at end of year		(414.9)	(459.6)
Current liabilities		(2.9)	(3)
Noncurrent liabilities		(412)	(456.6)
Net amount recognized at end of year	[2]	(414.9)	(459.6)
Unrecognized prior service cost	[3]	1	0.7
Unrecognized actuarial loss	[3]	835.5	925.6
Defined Benefit Plan Amounts Recognized In Other Comprehensive Income Or Regulatory Asset Or Liability	[3]	836.5	926.3
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation at beginning of year	[1]	525.8	716
Service cost		5	6.4		8.5
Interest cost		22	24.9		30.1
Plan participants' contributions		5.9	7.3
Plan amendments		7.5	0.1
Actuarial loss (gain)		1	(71.5)
Settlement Loss		0	0
Benefits paid		(38.9)	(43.7)
Estimated benefits paid by incurred subsidy		0.7	0.8
Projected Benefit Obligation Change Due to Separation		0	(114.5)
Plan Assets Change Due to Separation		0	(230.4)
Projected benefit obligation at end of year		529	525.8	[1]	716	[1]
Fair value of plan assets at beginning of year		225.9	465
Actual return on plan assets		13	1.9
Employer contributions		25.5	25.8
Fair value of plan assets at end of year		231.4	225.9		$ 465
Funded Status at end of year		(297.6)	(299.9)
Current liabilities		(0.7)	(0.6)
Net amount recognized at end of year	[2]	(297.6)	(299.9)
Unrecognized prior service cost	[3]	(29.2)	(41.6)
Unrecognized actuarial loss	[3]	68.3	66.1
Defined Benefit Plan Amounts Recognized In Other Comprehensive Income Or Regulatory Asset Or Liability	[3]	$ 39.1	$ 24.5
[1]	The change in benefit obligation for Pension Benefits represents the change in Projected Benefit Obligation while the change in benefit obligation for Other Postretirement Benefits represents the change in Accumulated Postretirement Benefit Obligation.
[2]	NiSource recognizes in its Consolidated Balance Sheets the underfunded and overfunded status of its various defined benefit postretirement plans, measured as the difference between the fair value of the plan assets and the benefit obligation.
[3]	NiSource determined that for certain rate-regulated subsidiaries the future recovery of pension and other postretirement benefits costs is probable. These rate-regulated subsidiaries recorded regulatory assets and liabilities of $847.5 million and $0.3 million, respectively, as of December 31, 2016, and $928.7 million and $8.1 million, respectively, as of December 31, 2015 that would otherwise have been recorded to accumulated other comprehensive loss.

Pension And Other Postretirem86

Pension And Other Postretirement Benefits (Schedule Of Significant Actuarial Assumptions In Determining Funded Status Plan) (Details)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Discount Rate	4.03%	4.24%
Rate of Compensation Increases	4.00%	4.00%
Trend for Next Year	0.00%	0.00%
Ultimate Trend	0.00%	0.00%
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Discount Rate	4.12%	4.33%
Rate of Compensation Increases	0.00%	0.00%
Trend for Next Year	8.43%	8.41%
Ultimate Trend	4.50%	4.50%
Year Ultimate Trend Reached	2,024	2,022

Pension And Other Postretirem87

Pension And Other Postretirement Benefits (Schedule Of One-Percentage-Point Change In Assumed Health Care Cost Trend Rates) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2016USD ($)
Defined Benefit Plan Disclosure [Line Items]
Effect on service and interest components of net periodic cost, 1% point increase	$ 1.3
Effect on service and interest components of net periodic cost, 1% point decrease	(1.1)
Effect on accumulated postretirement benefit obligation, 1% point increase	27.2
Effect on accumulated postretirement benefit obligation, 1% point decrease	$ (23.8)

Pension And Other Postretirem88

Pension And Other Postretirement Benefits (Schedule Of Expected Payments To Participants In Pension Plan) (Details) $ in Millions	Dec. 31, 2016USD ($)
Pension Plan
Defined Benefit Plan Disclosure [Line Items]
2,017	$ 171.9
2,018	172.5
2,019	171.1
2,020	171.2
2,021	172.2
2022-2026	816.8
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
2,017	34.1
2,018	34.9
2,019	35.8
2,020	36.5
2,021	37.2
2022-2026	180.9
Postretirement Health Coverage [Member]
Defined Benefit Plan Disclosure [Line Items]
2,017	0.7
2,018	0.7
2,019	0.7
2,020	0.7
2,021	0.7
2022-2026	$ 2.9

Pension And Other Postretirem89

Pension And Other Postretirement Benefits (Components Of The Plans' Net Periodic Benefits Cost) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Service Cost	$ 30.7	$ 34.8	$ 34.8
Interest cost	89.7	95.9	109
Expected return on assets	(132.9)	(167.2)	(181.1)
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)	(0.2)	0.1	0.2
Recognized actuarial loss	61.2	59.3	47.5
Net Periodic Benefit Costs	48.5	22.9	10.4
Settlement loss	0	2.5	0
Total Net Periodic Benefits Cost	48.5	25.4	10.4
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Service Cost	5	6.4	8.5
Interest cost	22	24.9	30.1
Expected return on assets	(17.2)	(28.2)	(36.8)
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)	(4.9)	(5.2)	(4.3)
Recognized actuarial loss	3.1	3.4	0.4
Net Periodic Benefit Costs	8	1.3	(2.1)
Settlement loss	0	0	0
Total Net Periodic Benefits Cost	$ 8	$ 1.3	$ (2.1)

Pension And Other Postretirem90

Pension And Other Postretirement Benefits (Schedule Of Key Assumptions That Were Used To Calculate The Net Periodic Benefits Cost) (Details)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Expected Long-Term Rate of Return on Plan Assets	8.00%
Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Discount Rate	4.24%	3.81%	4.50%
Expected Long-Term Rate of Return on Plan Assets	8.00%	8.30%	8.30%
Rate of Compensation Increases	4.00%	4.00%	4.00%
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Discount Rate	4.33%	3.94%	4.75%
Expected Long-Term Rate of Return on Plan Assets	7.85%	8.15%	8.14%
Rate of Compensation Increases	0.00%	0.00%	0.00%

Pension And Other Postretirem91

Pension And Other Postretirement Benefits (Schedule Of Changes In Plan Assets And Projected Benefit Obligations Recognized In Other Comprehensive Income) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Pension Plan
Net prior service cost/(credit)	$ 0	$ 0
Net actuarial (gain)/loss	(28.9)	125.7
Settlements	0	(2.5)	$ 0
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)	0.2	(0.1)	(0.2)
Less: amortization of net actuarial (gain) loss	(61.2)	(59.3)	(47.5)
Defined Benefit Plan Change Due to Separation	0	(143.8)
Total Recognized in Other Comprehensive Income or Regulatory Asset or Liability	(89.9)	(80)
Amount Recognized in Net Periodic Benefits Cost and Other Comprehensive Income or Regulatory Asset or Liability	(41.4)	(54.6)
Other Postretirement Benefits
Net prior service cost/(credit)	7.5	0.1
Net actuarial (gain)/loss	5.3	(45.2)
Settlements	0	0	0
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)	4.9	5.2	4.3
Less: amortization of net actuarial (gain) loss	(3.1)	(3.4)	$ (0.4)
Defined Benefit Plan Change Due to Separation	0	(21.5)
Total Recognized in Other Comprehensive Income or Regulatory Asset or Liability	14.6	(21.8)
Amount Recognized in Net Periodic Benefits Cost and Other Comprehensive Income or Regulatory Asset or Liability	$ 22.6	$ (20.5)

Common Stock (Details)

Common Stock (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Common Stock, Number of Shares, Par Value and Other Disclosures [Abstract]
Common stock, shares authorized	400,000,000	400,000,000
Common stock, par value	$ 0.01	$ 0.01
Common Stock, Dividends, Per Share, Cash Paid	$ 0.64	$ 0.83	$ 1.02
Dividend Declared	$ 0.175
Dividends Payable, Date to be Paid	Feb. 17, 2017
Dividends Payable, Date of Record	Feb. 10, 2017

Share-Based Compensation (Narra

Share-Based Compensation (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	May 12, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock available for awards, shares				8,000,000
Common stock reserved for future awards, shares	4,992,782
Stock-based employee compensation expense	$ 15.1	$ 18.8	$ 29.8
Related tax benefits	5.8	7.2	11.8
Excess Tax Benefit from Share-based Compensation, Operating Activities	7.2
Unrecognized compensation cost related to nonvested awards	$ 16.3
Weighted-average remaining requisite service period, years	1 year 8 months
401(k) match, profit sharing and non-elective expense	$ 32.3	$ 27.4	$ 28.1
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay	3.00%
Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted	647,305		535,037
Fair value of shares granted	$ 12.6		$ 16.6
Shares nonvested	647,305	0
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted	65,418	660,230	158,633
Fair value of shares granted	$ 1.4	$ 23.9	$ 5.2
Shares vesting period, (years)	3 years
Shares nonvested	1,642,030	3,142,473
Performance Shares Converted to Restricted Stock Unites as a result of the Separation		736,911
Omnibus Plan | Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Units issued	218,581
Director Plan | Non-Employee Director Award
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares nonvested	40,932
2016 Award | Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares nonvested	65,418
2015 Award | Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares nonvested	750,708
2014 Award | Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares nonvested	46,810

Share-Based Compensation (Sched

Share-Based Compensation (Schedule Of Transactions Of Restricted Stock Unit) (Details) - Restricted Stock Units (RSUs) - $ / shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Nonvested, Other Than Options	3,142,473
Nonvested, Weighted Average Grant Date Fair Value	$ 8.55
Granted, Other Than Options	65,418	660,230	158,633
Granted, Weighted Average Grant Date Fair Value	$ 21.49
Forfeited, Other Than Options	(46,447)
Forfeited, Weighted Average Grant Date Fair Value	$ 11.71
Vested, Other Than Options	(1,519,414)
Vested, Weighted Average Grant Date Fair Value	$ 5.21
Nonvested, Other Than Options	1,642,030	3,142,473
Nonvested, Weighted Average Grant Date Fair Value	$ 12.05	$ 8.55

Share-Based Compensation (Sch95

Share-Based Compensation (Schedule Of Transactions Of Contingent Awards) (Details) - Performance Shares - $ / shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Nonvested, Other Than Options	0
Nonvested, Weighted Average Grant Date Fair Value	$ 0
Granted, Other Than Options	647,305	535,037
Granted, Weighted Average Grant Date Fair Value	$ 19.50
Forfeited, Other Than Options	0
Forfeited, Weighted Average Grant Date Fair Value	$ 0
Vested, Other Than Options	0
Vested, Weighted Average Grant Date Fair Value	$ 0
Nonvested, Other Than Options	647,305
Nonvested, Weighted Average Grant Date Fair Value	$ 19.50

Long-Term Debt (Narrative) (Det

Long-Term Debt (Narrative) (Details) - USD ($) $ in Millions

12 Months Ended

Dec. 31, 2016

Dec. 31, 2015

Dec. 31, 2014

Nov. 28, 2016

Nov. 01, 2016

Jun. 30, 2016

Jun. 24, 2016

Mar. 31, 2016

Mar. 15, 2016

Nov. 28, 2015

May 22, 2015

May 18, 2015

Debt Instrument [Line Items]

Debt Instrument, Convertible, Conversion Ratio

66

Notional Amount of Forward-Starting Interest rate Swap Agreements

$ 1,500

$ 1,000

$ 500

Loss on early extinguishment of long-term debt

0

(97.2)

$ 0

Cross default provision on default relating to any indebtedness

50

Security interest and other subset of asset

$ 150

Asset sale covenant percentage of consolidated total assets

10.00%

Percentage of additional subset of assets capped

10.00%

NiSource Finance

Debt Instrument [Line Items]

Subsidiary Ownership Percentage

100.00%

Debt Instrument Tendered

750

Debt Instrument, Repurchased Face Amount

$ 291.5

Extinguishment of Debt, Amount

1,075

Loss on early extinguishment of long-term debt

(97.2)

Notional Amount of Fixed Floating Interest Rate Swaps Total

$ 1,000

NiSource Finance | Variable Rate Term Loan

Debt Instrument [Line Items]

Long-term Debt

$ 500

$ 500

NiSource Finance | 6.40% Notes Due 2018

Debt Instrument [Line Items]

Interest rate on debt

6.40%

debt instrument year wise maturity date

2,018

Debt Instrument, Maturity Date

Mar. 31, 2018

NiSource Finance | 4.45% Notes Due 2021

Debt Instrument [Line Items]

Interest rate on debt

4.45%

debt instrument year wise maturity date

2,021

Debt Instrument, Maturity Date

Dec. 31, 2021

NiSource Finance | Interest Rate Swap

Debt Instrument [Line Items]

Loss on Fair Value Hedge Ineffectiveness

$ 0

Notional Amount of Forward-Starting Interest rate Swap Agreements

$ 500

NiSource Finance | Long Term Unsecured Notes Due 2015

Debt Instrument [Line Items]

Interest rate on debt

5.36%

Debt Instrument, Repurchase Amount

$ 230

NiSource Finance | 5.25% Notes Due 2017

Debt Instrument [Line Items]

Interest rate on debt

5.25%

debt instrument year wise maturity date

2,017

Debt Instrument, Maturity Date

Sep. 30, 2017

NiSource Finance | 5.41% Notes Due 2016

Debt Instrument [Line Items]

Debt Instrument, Maturity Date

Nov. 30, 2016

NiSource Finance | Long Term Unsecured Notes Due 2016

Debt Instrument [Line Items]

Debt Instrument, Repurchased Face Amount

$ 90

$ 201.5

Interest rate on debt

5.41%

10.75%

NiSource Finance | 10.75% Notes Due 2016

Debt Instrument [Line Items]

Debt Instrument, Maturity Date

Mar. 31, 2016

NiSource Finance | Variable Rate due 2019

Debt Instrument [Line Items]

Debt Instrument, Maturity Date

Mar. 29, 2019

NIPSCO | Pollution Control Bond

Debt Instrument [Line Items]

Debt Instrument, Repurchased Face Amount

$ 130

Interest rate on debt

5.60%

Columbia Pipeline Group

Debt Instrument [Line Items]

Face amount of notes

$ 2,750

Maximum

Debt Instrument [Line Items]

Cross default provision on default relating to any indebtedness

$ 50

Minimum

Debt Instrument [Line Items]

Cross default provision on default relating to any indebtedness

$ 5

Revolving Credit Facility | Maximum

Debt Instrument [Line Items]

Debt Instrument, Convertible, Conversion Ratio

70

Private Placement | Maximum

Debt Instrument [Line Items]

Debt Instrument, Convertible, Conversion Ratio

75

Long-Term Debt (Schedule of Con

Long-Term Debt (Schedule of Consolidated Long-Term Debt (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Senior Notes		$ 5,968	$ 5,759.5
Medium-Term Notes		241.5	241.5
Capital Lease Obligations		157.4	198.6
Long-term Debt, Excluding Current Maturities		6,421.3	6,382.2
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net		$ (41.6)	(45.5)
NiSource Finance
Debt Instrument [Line Items]
Senior Notes	[1]		0
NiSource Finance | 10.75% Notes Due 2016
Debt Instrument [Line Items]
Debt Instrument, Maturity Date		Mar. 31, 2016
Debt, Weighted Average Interest Rate		10.75%
Senior Notes		$ 0	201.5
NiSource Finance | 5.41% Notes Due 2016
Debt Instrument [Line Items]
Debt Instrument, Maturity Date		Nov. 30, 2016
Debt, Weighted Average Interest Rate		5.41%
Senior Notes		$ 0	90
NiSource Finance | 5.25% Notes Due 2017
Debt Instrument [Line Items]
Debt Instrument, Maturity Date		Sep. 30, 2017
Debt, Weighted Average Interest Rate		5.25%
Senior Notes		$ 210.4	210.4
NiSource Finance | 6.40% Notes Due 2018
Debt Instrument [Line Items]
Debt Instrument, Maturity Date		Mar. 31, 2018
Debt, Weighted Average Interest Rate		6.40%
Senior Notes		$ 476	476
NiSource Finance | 6.80% Notes Due 2019
Debt Instrument [Line Items]
Debt Instrument, Maturity Date		Jan. 31, 2019
Debt, Weighted Average Interest Rate		6.80%
Senior Notes		$ 500	500
NiSource Finance | Variable Rate due 2019
Debt Instrument [Line Items]
Debt Instrument, Maturity Date		Mar. 29, 2019
Senior Notes	[1]	$ 500
NiSource Finance | 5.45% Notes due 2020
Debt Instrument [Line Items]
Debt Instrument, Maturity Date		Sep. 30, 2020
Debt, Weighted Average Interest Rate		5.45%
Senior Notes		$ 550	550
NiSource Finance | 4.45% Notes Due 2021
Debt Instrument [Line Items]
Debt Instrument, Maturity Date		Dec. 31, 2021
Debt, Weighted Average Interest Rate		4.45%
Senior Notes		$ 63.6	63.6
NiSource Finance | 6.13% Notes Due 2022
Debt Instrument [Line Items]
Debt Instrument, Maturity Date		Mar. 31, 2022
Debt, Weighted Average Interest Rate		6.13%
Senior Notes		$ 500	500
NiSource Finance | 3.85% Notes Due 2023
Debt Instrument [Line Items]
Debt Instrument, Maturity Date		Feb. 28, 2023
Debt, Weighted Average Interest Rate		3.85%
Senior Notes		$ 250	250
NiSource Finance | 5.89% Notes Due 2025
Debt Instrument [Line Items]
Debt Instrument, Maturity Date		Nov. 30, 2025
Debt, Weighted Average Interest Rate		5.89%
Senior Notes		$ 265	265
NiSource Finance | 6.25% Notes Due 2040
Debt Instrument [Line Items]
Debt Instrument, Maturity Date		Dec. 31, 2040
Debt, Weighted Average Interest Rate		6.25%
Senior Notes		$ 250	250
NiSource Finance | 5.95% Notes Due 2041
Debt Instrument [Line Items]
Debt Instrument, Maturity Date		Jun. 30, 2041
Debt, Weighted Average Interest Rate		5.95%
Senior Notes		$ 400	400
NiSource Finance | 5.80% Notes Due 2042
Debt Instrument [Line Items]
Debt Instrument, Maturity Date		Feb. 28, 2042
Debt, Weighted Average Interest Rate		5.80%
Senior Notes		$ 250	250
NiSource Finance | 5.25% Notes Due 2043
Debt Instrument [Line Items]
Debt Instrument, Maturity Date		Feb. 28, 2043
Debt, Weighted Average Interest Rate		5.25%
Senior Notes		$ 500	500
NiSource Finance | 4.80% Notes due 2044
Debt Instrument [Line Items]
Debt Instrument, Maturity Date		Feb. 29, 2044
Debt, Weighted Average Interest Rate		4.80%
Senior Notes		$ 750	750
NiSource Finance | 5.65% Notes Due 2045
Debt Instrument [Line Items]
Debt Instrument, Maturity Date		Feb. 28, 2045
Debt, Weighted Average Interest Rate		5.65%
Senior Notes		$ 500	500
Nisource Capital Markets Inc | 6.78% Notes Due 2027
Debt Instrument [Line Items]
Debt Instrument, Maturity Date		Dec. 31, 2027
Debt, Weighted Average Interest Rate		6.78%
Senior Notes		$ 3	3
Nisource Capital Markets Inc | 7.92% Notes Due 2027
Debt Instrument [Line Items]
Debt, Weighted Average Interest Rate		7.92%
Medium-Term Notes		$ 106	106
Nisource Capital Markets Inc | 7.92% Notes Due 2027 | Maximum
Debt Instrument [Line Items]
Debt Instrument, Maturity Date		May 31, 2027
Nisource Capital Markets Inc | 7.92% Notes Due 2027 | Minimum
Debt Instrument [Line Items]
Debt Instrument, Maturity Date		Mar. 31, 2017
Columbia Of Massachusetts | 6.30% Notes Due 2028
Debt Instrument [Line Items]
Debt, Weighted Average Interest Rate		6.30%
Medium-Term Notes		$ 40	40
Columbia Of Massachusetts | 6.30% Notes Due 2028 | Maximum
Debt Instrument [Line Items]
Debt Instrument, Maturity Date		Feb. 29, 2028
Columbia Of Massachusetts | 6.30% Notes Due 2028 | Minimum
Debt Instrument [Line Items]
Debt Instrument, Maturity Date		Dec. 31, 2025
Columbia Of Massachusetts | 5.33% notes Due 2036
Debt Instrument [Line Items]
Debt, Weighted Average Interest Rate		5.33%
Capital Lease Obligations		$ 23.7	24.1
Columbia Of Massachusetts | 5.33% notes Due 2036 | Maximum
Debt Instrument [Line Items]
Debt Instrument, Maturity Date		Jul. 31, 2036
Columbia Of Massachusetts | 5.33% notes Due 2036 | Minimum
Debt Instrument [Line Items]
Debt Instrument, Maturity Date		Dec. 31, 2033
NIPSCO | 7.57% Notes Due 2027
Debt Instrument [Line Items]
Debt, Weighted Average Interest Rate		7.57%
Medium-Term Notes		$ 95.5	95.5
NIPSCO | 7.57% Notes Due 2027 | Maximum
Debt Instrument [Line Items]
Debt Instrument, Maturity Date		Aug. 31, 2027
NIPSCO | 7.57% Notes Due 2027 | Minimum
Debt Instrument [Line Items]
Debt Instrument, Maturity Date		Jun. 30, 2017
NIPSCO | 3.95% Notes Due 2018
Debt Instrument [Line Items]
Debt Instrument, Maturity Date		May 31, 2018
Debt, Weighted Average Interest Rate		3.95%
Capital Lease Obligations		$ 12.7	52.8
NIPSCO | 5.76% Notes Due 2019
Debt Instrument [Line Items]
Debt, Weighted Average Interest Rate		5.76%
Long-term Pollution Control Bond		$ 96	226
NIPSCO | 5.76% Notes Due 2019 | Maximum
Debt Instrument [Line Items]
Debt Instrument, Maturity Date		Apr. 30, 2019
NIPSCO | 5.76% Notes Due 2019 | Minimum
Debt Instrument [Line Items]
Debt Instrument, Maturity Date		Jul. 31, 2017
Columbia Of Ohio | 6.53% Notes Due 2038
Debt Instrument [Line Items]
Debt, Weighted Average Interest Rate		6.53%
Capital Lease Obligations		$ 80.1	79.8
Columbia Of Ohio | 6.53% Notes Due 2038 | Maximum
Debt Instrument [Line Items]
Debt Instrument, Maturity Date		Jun. 30, 2038
Columbia Of Ohio | 6.53% Notes Due 2038 | Minimum
Debt Instrument [Line Items]
Debt Instrument, Maturity Date		Oct. 31, 2021
Ni Source Corporate Services | 2.92% Notes Due 2021
Debt Instrument [Line Items]
Debt, Weighted Average Interest Rate		2.92%
Capital Lease Obligations		$ 3.5	3.7
Ni Source Corporate Services | 2.92% Notes Due 2021 | Maximum
Debt Instrument [Line Items]
Debt Instrument, Maturity Date		Apr. 30, 2021
Ni Source Corporate Services | 2.92% Notes Due 2021 | Minimum
Debt Instrument [Line Items]
Debt Instrument, Maturity Date		Oct. 31, 2019
Columbia Of Virginia | 12.27% Notes Due 2029
Debt Instrument [Line Items]
Debt, Weighted Average Interest Rate		12.27%
Capital Lease Obligations		$ 5.5	5.8
Columbia Of Virginia | 12.27% Notes Due 2029 | Maximum
Debt Instrument [Line Items]
Debt Instrument, Maturity Date		Jul. 31, 2029
Columbia Of Virginia | 12.27% Notes Due 2029 | Minimum
Debt Instrument [Line Items]
Debt Instrument, Maturity Date		Aug. 31, 2024
Columbia Of Pennsylvania | 5.45% Notes Due 2036
Debt Instrument [Line Items]
Debt, Weighted Average Interest Rate		5.45%
Capital Lease Obligations		$ 31.9	32.4
Columbia Of Pennsylvania | 5.45% Notes Due 2036 | Maximum
Debt Instrument [Line Items]
Debt Instrument, Maturity Date		Jun. 30, 2036
Columbia Of Pennsylvania | 5.45% Notes Due 2036 | Minimum
Debt Instrument [Line Items]
Debt Instrument, Maturity Date		Aug. 31, 2027
Nisource Development Company Inc | 5.56% Notes Due 2041
Debt Instrument [Line Items]
Debt Instrument, Maturity Date		Jul. 31, 2041
Debt, Weighted Average Interest Rate		5.56%
Notes Payable		$ 0	$ 2.1
[1]	Rate of one month Libor plus 95 basis points.

Short-Term Borrowings (Narrativ

Short-Term Borrowings (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Short-term Debt [Line Items]
Commercial paper outstanding	$ 1,178	$ 321.4
Line of Credit Facility, Amount Outstanding	0	0
Accounts receivable securitization facility borrowings	310	246
Commercial Paper
Short-term Debt [Line Items]
Revolving credit facility, maximum	1,500
Revolving Credit Facility
Short-term Debt [Line Items]
Revolving credit facility, maximum	$ 1,850	1,500
Revolving credit facility, termination date	Nov. 28, 2021
Standby Letters of Credit
Short-term Debt [Line Items]
Line of Credit Facility, Amount Outstanding	$ 14.7	$ 14.7

Short-Term Borrowings (Schedule

Short-Term Borrowings (Schedule Of Short-Term Borrowings) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Short-term Debt [Line Items]
Commercial paper	$ 1,178	$ 321.4
Credit facilities borrowings	0	0
Accounts receivable securitization facility borrowings	310	246
Total short-term borrowings	$ 1,488	$ 567.4
Commercial Paper
Short-term Debt [Line Items]
Commercial Paper/credit facilities borrowings, weighted average interest rate	1.24%	1.00%
Revolving Credit Facility
Short-term Debt [Line Items]
Commercial Paper/credit facilities borrowings, weighted average interest rate	0.00%	0.00%
Standby Letters of Credit
Short-term Debt [Line Items]
Credit facilities borrowings	$ 14.7	$ 14.7

Fair Value (Narrative) (Details

Fair Value (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 04, 2015
Fair Value Disclosure [Line Items]
Transfers between Fair Value Hierarchies	0
U.S. Treasury debt securities
Fair Value Disclosure [Line Items]
Net realized gain on available for sale debt securities	$ 0	$ 0.2	$ 0.1
Available-for-sale securities, maturities of less than a year	0.5
Corporate/Other debt securities
Fair Value Disclosure [Line Items]
Net realized gain on available for sale debt securities	0.2	$ 0.2	$ 0.4
Available-for-sale securities, maturities of less than a year	$ 15.2
NiSource Finance
Fair Value Disclosure [Line Items]
Notional value of interest rate swap				$ 500

Fair Value (Fair Value Of Finan

Fair Value (Fair Value Of Financial Assets And Liabilities Measured On A Recurring Basis) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Risk management assets	$ 49	$ 0.1
Available-for-sale securities	131.5	128.7
Fair value assets measured on recurring basis, total	180.5	128.8
Risk management liabilities	61.3	31.9
Fair value liabilities measured on recurring basis, total	61.3	31.9
Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Risk management assets	5.4	0.1
Available-for-sale securities	0	0
Fair value assets measured on recurring basis, total	5.4	0.1
Risk management liabilities	1.2	14.3
Fair value liabilities measured on recurring basis, total	1.2	14.3
Significant Other Observable Inputs (Level 2) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Risk management assets	43.6	0
Available-for-sale securities	131.5	128.7
Fair value assets measured on recurring basis, total	175.1	128.7
Risk management liabilities	58.9	17.4
Fair value liabilities measured on recurring basis, total	58.9	17.4
Significant Unobservable Inputs (Level 3) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Risk management assets	0	0
Available-for-sale securities	0	0
Fair value assets measured on recurring basis, total	0	0
Risk management liabilities	1.2	0.2
Fair value liabilities measured on recurring basis, total	$ 1.2	$ 0.2

Fair Value (Available-For-Sale

Fair Value (Available-For-Sale Securities) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Fair Value Disclosure [Line Items]
Amortized Cost	$ 133.7	$ 129.4
Gross Unrealized Gains	0.4	0.4
Gross Unrealized Losses	(2.6)	(1.1)
Available-for-sale Securities	131.5	128.7
U.S. Treasury debt securities
Fair Value Disclosure [Line Items]
Amortized Cost	35	33.7
Gross Unrealized Gains	0.1	0.1
Gross Unrealized Losses	(0.6)	(0.3)
Available-for-sale Securities	34.5	33.5
Corporate/Other debt securities
Fair Value Disclosure [Line Items]
Amortized Cost	98.7	95.7
Gross Unrealized Gains	0.3	0.3
Gross Unrealized Losses	(2)	(0.8)
Available-for-sale Securities	$ 97	$ 95.2

Fair Value (Carrying Amount And

Fair Value (Carrying Amount And Estimated Fair Values Of Financial Instruments) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Fair Value Disclosures [Abstract]
Long-term debt (including current portion), Carrying Amount	$ 6,421.3	$ 6,382.2
Long-term debt (including current portion), Estimated Fair Value	$ 7,064.1	$ 6,975.7

Transfers Of Financial Asset104

Transfers Of Financial Assets (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Net receivables transferred	$ 310	$ 246
Accounts receivable securitization facility borrowings	310	246
Cash from financing activities	64	38.3
Securitization transaction fees	2.3	$ 2.5	$ 2.9
Accounts Receivable Program | Maximum
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Accounts receivable securitization facility borrowings	310
Columbia Gas Of Ohio Receivables Corporation
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Net receivables transferred	100
Columbia Gas Of Ohio Receivables Corporation | Maximum
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Trade receivables, seasonal program maximum	240
NIPSCO Accounts Receivable Corporation
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Net receivables transferred	175
NIPSCO Accounts Receivable Corporation | Maximum
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Trade receivables, seasonal program maximum	200
Columbia Gas Of Pennsylvania Receivables Corporation
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Net receivables transferred	35
Columbia Gas Of Pennsylvania Receivables Corporation | Maximum
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Trade receivables, seasonal program maximum	$ 75

Transfers Of Financial Asset105

Transfers Of Financial Assets (Schedule Of Gross And Net Receivables Transferred As Well As Short-Term Borrowings Related To The Securitization Transactions) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Transfers and Servicing [Abstract]
Gross Receivables interest	$ 618.3	$ 450.8
Less: Receivables not transferred	308.3	204.8
Net receivables transferred	310	246
Accounts receivable securitization agreements outstanding	$ 310	$ 246

Other Commitments And Contin106

Other Commitments And Contingencies (Narrative) (Details) $ in Millions	Apr. 17, 2015USD ($)	Jul. 31, 2008MW	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)
Other Commitments And Contingencies [Line Items]
Payments made in connection with operating leases			$ 52	$ 47.5	$ 59.8
Capital lease payments			167	236.2
Capital leases related accumulated depreciation			20.6	44
Wind power purchase agreement capacity | MW		100
Each wind power purchase agreement capacity | MW		50
Line of Credit Facility, Amount Outstanding			0	0
Recorded reserves to cover environmental remediation at various sites			111.4	123.2
Estimated Cost of Compliance with Coal Combustion Residuals, Maximum	$ 230
Estimated Cost of Compliance with Effluent Limitations Guidelines			$ 170
Transmission Upgrade Agreement Multiplier			1.71
Liability Associated with Bailey Generating Station Retirement			$ 22.1
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount			0
Payments Pure Air			21.7	19.5
Liability Associated with Bailly Generating Station Retirement - Pure Air Contract Termination Portion			$ 16
MGP Sites
Other Commitments And Contingencies [Line Items]
Number of waste disposal sites identified by program			64
Liability for estimated remediation costs			$ 105.5	110.4
Reasonably possible remediation costs variance from reserve			25
NIPSCO
Other Commitments And Contingencies [Line Items]
Upgrade Sponsors Liability related to Portion Collected for Taxes on TUA			$ 8.6
Maximum
Other Commitments And Contingencies [Line Items]
Long term purchase commitment time period			20 years
Minimum
Other Commitments And Contingencies [Line Items]
Long term purchase commitment time period			15 years
Minimum | NIPSCO
Other Commitments And Contingencies [Line Items]
Cost to Maintain and Operate Current Fleet of Coal-Fired Generating Units			$ 1,000
Pipeline Capacity Transportation And Storage | Maximum
Other Commitments And Contingencies [Line Items]
Long Term Purchase Commitment Expiration Year			2,045
Pipeline Capacity Transportation And Storage | Minimum
Other Commitments And Contingencies [Line Items]
Long Term Purchase Commitment Expiration Year			2,017
Coal Transportation | Maximum
Other Commitments And Contingencies [Line Items]
Long Term Purchase Commitment Expiration Year			2,018
Standby Letters of Credit
Other Commitments And Contingencies [Line Items]
Line of Credit Facility, Amount Outstanding			$ 14.7	$ 14.7

Other Commitments And Contin107

Other Commitments And Contingencies Other Commitments and Contingencies (Contractual Obligation, Fiscal Year Maturity Schedule) (Details) - USD ($) $ in Millions		Dec. 31, 2016	Dec. 31, 2015
Long-term Purchase Commitment [Line Items]
Long-term Debt, Future Minimum Payments Due	[1]	$ 6,305.5
Long-term Debt, Future Minimum Payments Due, Next Twelve Months	[1]	349.9
Long-term Debt, Future Minimum Payments, Due in Two Years	[1]	476
Long-term Debt, Future Minimum Payments, Due in Three Years	[1]	1,041
Long-term Debt, Future Minimum Payments, Due in Four Years	[1]	550
Long-term Debt, Future Minimum Payments, Due in Five Years	[1]	63.6
Long-term Debt, Future Minimum Payments, Due Thereafter	[1]	3,825
Capital Leases, Future Minimum Payments Due	[2]	250
Capital Leases, Future Minimum Payments Due, Next Twelve Months	[2]	22.7
Capital Leases, Future Minimum Payments Due in Two Years	[2]	18.5
Capital Leases, Future Minimum Payments Due in Three Years	[2]	14.2
Capital Leases, Future Minimum Payments Due in Four Years	[2]	13.5
Capital Leases, Future Minimum Payments Due in Five Years	[2]	13.4
Capital Leases, Future Minimum Payments Due Thereafter	[2]	167.7
Interest Payments on Long-term Debt, Future Minimum Payments Due		4,611.2
Interest Payments on Long-term Debt, Future Minimum Payments Due, Next Twelve Months		337.9
Interest Payments on Long-term Debt, Future Minimum Payments, Due in Two Years		305.3
Interest Payments on Long-term Debt, Future Minimum Payments, Due in Three Years		265.2
Interest Payments on Long-term Debt, Future Minimum Payments, Due in Four Years		244.9
Interest Payments on Long-term Debt, Future Minimum Payments, Due in Five Years		214.9
Interest Payments on Long-term Debt, Future Minimum Payments, Due Thereafter		3,243
Operating Leases, Future Minimum Payments Due	[3]	54.6
Operating Leases, Future Minimum Payments Due, Next Twelve Months	[3]	15.4
Operating Leases, Future Minimum Payments, Due in Two Years	[3]	9.4
Operating Leases, Future Minimum Payments, Due in Three Years	[3]	7.5
Operating Leases, Future Minimum Payments, Due in Four Years	[3]	4.8
Operating Leases, Future Minimum Payments, Due in Five Years	[3]	4.1
Operating Leases, Future Minimum Payments, Due Thereafter	[3]	13.4
Energy Commodity Contracts, Future Minimum Payments Due	[4]	312.1
Energy Commodity Contracts, Future Minimum Payments Due, Next Twelve Months	[4]	108.5
Energy Commodity Contracts, Future Minimum Payments, Due in Two Years	[4]	67.7
Energy Commodity Contracts, Future Minimum Payments, Due in Three Years	[4]	67.3
Energy Commodity Contracts, Future Minimum Payments, Due in Four Years	[4]	68
Energy Commodity Contracts, Future Minimum Payments, Due in Five Years	[4]	0.6
Energy Commodity Contracts, Future Minimum Payments, Due Thereafter	[4]	0
Service Obligations, Pipeline Service Obligations, Future Minimum Payments Due		2,002.1
Service Obligations, Pipeline Service Obligations, Future Minimum Payments Due, Next Twelve Months		532.7
Service Obligations, Pipeline Service Obligations, Future Minimum Payments, Due in Two Years		382.7
Service Obligations, Pipeline Service Obligations, Future Minimum Payments, Due in Three Years		293.1
Service Obligations, Pipeline Service Obligations, Future Minimum Payments, Due in Four Years		176
Service Obligations, Pipeline Service Obligations, Future Minimum Payments, Due in Five Years		139.2
Service Obligations, Pipeline Service Obligations, Future Minimum Payments, Due Thereafter		478.4
Service Obligations, IBM Service Obligations, Future Minimum Payments Due		325
Service Obligations, IBM Service Obligations, Future Minimum Payments Due, Next Twelve Months		84.1
Service Obligations, IBM Service Obligations, Future Minimum Payments, Due in Two Years		81.2
Service Obligations, IBM Service Obligations, Future Minimum Payments, Due in Three Years		80
Service Obligations, IBM Service Obligations, Future Minimum Payments, Due in Four Years		79.7
Service Obligations, IBM Service Obligations, Future Minimum Payments, Due in Five Years		0
Service Obligations, IBM Service Obligations, Future Minimum Payments, Due Thereafter		0
Service Obligations, Other Service Obligations, Future Minimum Payments Due		77.7
Service Obligations, Other Service Obligations, Future Minimum Payments Due, Next Twelve Months		58.1
Service Obligations, Other Service Obligations, Future Minimum Payments, Due in Two Years		17.4
Service Obligations, Other Service Obligations, Future Minimum Payments, Due in Three Years		1.9
Service Obligations, Other Service Obligations, Future Minimum Payments, Due in Four Years		0.3
Service Obligations, Other Service Obligations, Future Minimum Payments, Due in Five Years		0
Service Obligations, Other Service Obligations, Future Minimum Payments, Due Thereafter		0
Other Liabilities, Future Minimum Payments Due		34.4
Other Liabilities, Future Minimum Payments Due, Next Twelve Months		34.4
Other Liabilities, Future Minimum Payments, Due in Two Years		0
Other Liabilities, Future Minimum Payments, Due in Three Years		0
Other Liabilities, Future Minimum Payments, Due in Four Years		0
Other Liabilities, Future Minimum Payments, Due in Five Years		0
Other Liabilities, Future Minimum Payments, Due Thereafter		0
Total Future Minimum Lease Payments Due		13,972.6
Total Future Minimum Lease Payments Due, Next Twelve Months		1,543.7
Total Future Minimum Lease Payments, Due in Two Years		1,358.2
Total Future Minimum Lease Payments, Due in Three Years		1,770.2
Total Future Minimum Lease Payments, Due in Four Years		1,137.2
Total Future Minimum Lease Payments, Due in Five Years		435.8
Total Future Minimum Lease Payments, Due Thereafter		7,727.5
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net		(41.6)	$ (45.5)
Capital Leases, Future Minimum Payments, Interest Included in Payments		92.6
Fleet Lease
Long-term Purchase Commitment [Line Items]
Operating Leases, Future Minimum Payments Due, Next Twelve Months		31.1
Operating Leases, Future Minimum Payments, Due in Two Years		32.9
Operating Leases, Future Minimum Payments, Due in Three Years		26.1
Operating Leases, Future Minimum Payments, Due in Four Years		17.5
Operating Leases, Future Minimum Payments, Due in Five Years		8
Operating Leases, Future Minimum Payments, Due Thereafter		2
NIPSCO Coal Contracts
Long-term Purchase Commitment [Line Items]
Energy Commodity Contracts, Future Minimum Payments Due, Next Twelve Months		24.2
Energy Commodity Contracts, Future Minimum Payments, Due in Two Years		$ 10.1
[1]	Long-term debt balance excludes unamortized issuance costs and discounts of $41.6 million.
[2]	Capital lease payments shown above are inclusive of interest totaling $92.6 million.
[3]	Operating lease balances do not include amounts for fleet leases that can be renewed beyond the initial lease term. The Company anticipates renewing the leases beyond the initial term, but the anticipated payments associated with the renewals do not meet the definition of expected minimum lease payments and therefore are not included above. Expected payments are $31.1 million in 2017, $32.9 million in 2018, $26.1 million in 2019, $17.5 million in 2020, $8.0 million in 2021 and $2.0 million thereafter.
[4]	)In January 2017, NIPSCO signed new coal contract commitments of $24.2 million and $10.1 million for 2017 and 2018, respectively. These contracts are not included above.

Accumulated Other Comprehens108

Accumulated Other Comprehensive Loss (Components Of Accumulated Other Comprehensive Loss) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax		$ 7.6	$ (16.5)	$ (9.6)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax		2.4	5.5	2.6
Net current-period other comprehensive income (loss)		10	(11)	(7)
Allocation of AOCI to Noncontrolling Interest	[1]		2
Distribution of CPG to shareholders			24.5
Accumulated other comprehensive loss		(25.1)	(35.1)	(50.6)	$ (43.6)
Gains and Losses on Securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax		0	(0.5)	0.9
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax		(0.1)	(0.3)	(0.3)
Net current-period other comprehensive income (loss)		(0.1)	(0.8)	0.6
Allocation of AOCI to Noncontrolling Interest			0
Distribution of CPG to shareholders			0
Accumulated other comprehensive loss		(0.6)	(0.5)	0.3	(0.3)
Gains and Losses on Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax		7.1	(11)	(0.3)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax		1.5	3.2	2.5
Net current-period other comprehensive income (loss)		8.6	(7.8)	2.2
Allocation of AOCI to Noncontrolling Interest			2
Distribution of CPG to shareholders			13.9
Accumulated other comprehensive loss		(6.9)	(15.5)	(23.6)	(25.8)
Pension and OPEB Items
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax		0.5	(5)	(10.2)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax		1	2.6	0.4
Net current-period other comprehensive income (loss)		1.5	(2.4)	(9.8)
Allocation of AOCI to Noncontrolling Interest			0
Distribution of CPG to shareholders			10.6
Accumulated other comprehensive loss		$ (17.6)	$ (19.1)	$ (27.3)	$ (17.5)
[1]	This transaction, which occurred prior to the Separation, was distributed through retained earnings as part of the Separation on July 1, 2015.

Other, Net (Schedule Of Other N

Other, Net (Schedule Of Other Net) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Other Nonoperating Income (Expense) [Abstract]
Interest income		$ 3.4	$ 0.8	$ 3.8
AFUDC Equity		11.6	11.5	10.7
Charitable Contributions		(4.5)	(4.8)	(11.1)
Miscellaneous	[1]	(9)	9.9	10
Total Other, net		1.5	$ 17.4	$ 13.4
TUA Related Charge		$ 8.6
[1]	Miscellaneous in 2016 primarily consists of a TUA-related charge of $8.6 million to reflect the estimated amount owed to the upgrade sponsors for the portion of the multiplier previously collected for taxes. Refer to Note 18-E, "Other Matters," for additional information. In 2015 and 2014, Miscellaneous primarily consisted of TUA income.

Interest Expense, Net (Details)

Interest Expense, Net (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Interest Expense [Abstract]
Interest on long-term debt		$ 352.3	$ 377.5	$ 368.6
Interest on short-term borrowings		9.2	2.2	5.2
Debt discount/cost amortization		7.6	8.7	8
Accounts receivable securitization fees		2.3	2.5	2.9
Allowance for borrowed funds used and interest capitalized during construction		(5.6)	(5.4)	(5.3)
Other	[1]	(16.3)	(5.3)	0.1
Total Interest Expense, net		$ 349.5	$ 380.2	$ 379.5
[1]	The change in Other for 2016 is primarily attributed to increases in Columbia of Ohio's post-in-service carrying charges (PISCC).

Segments Of Business (Narrative

Segments Of Business (Narrative) (Details)	12 Months Ended
	Dec. 31, 2016
Segment Reporting [Abstract]
Number of Reportable Segments	2
Number of counties in which electric service provided by Electric Operations	20

Segments Of Business (Schedule

Segments Of Business (Schedule Of Operating Income Derived From Revenues And Expenses By Segment) (Details) - USD ($) $ in Millions		3 Months Ended										12 Months Ended
		Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	[1]	Mar. 31, 2016	[1]	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Segment Reporting Information [Line Items]
Unaffiliated												$ 4,492.5	$ 4,651.8	$ 5,272.4
Operating Income		$ 224.9	$ 113.7	$ 138.2		$ 381.4		$ 219.5	$ 109.7	$ 84.4	$ 386.3	858.2	799.9	789.1
Consolidated Depreciation and Amortization												547.1	524.4	486.9
Consolidated Assets		18,691.9						17,492.5				18,691.9	17,492.5	24,589.8
Payments to Acquire Property Plant and Equipment Including Captial Expenditures From Current Liabilities And Equity Method Investments	[2]											1,490.4	1,367.5	1,339.6
Gas Distribution Operations
Segment Reporting Information [Line Items]
Unaffiliated												2,830.6	3,069.1	3,593.9
Operating Income												574	555.8	537
Consolidated Depreciation and Amortization												252.9	232.6	217.6
Consolidated Assets		11,096.4						10,094.5				11,096.4	10,094.5	9,443.7
Payments to Acquire Property Plant and Equipment Including Captial Expenditures From Current Liabilities And Equity Method Investments	[2]											1,054.4	917	860.3
Electric Operations
Segment Reporting Information [Line Items]
Unaffiliated												1,661.6	1,574.4	1,673.4
Operating Income												291.4	264.4	282.7
Consolidated Depreciation and Amortization												274.5	267.7	244.4
Consolidated Assets		5,233.3						5,265.3				5,233.3	5,265.3	5,009.9
Payments to Acquire Property Plant and Equipment Including Captial Expenditures From Current Liabilities And Equity Method Investments	[2]											420.6	400.3	438.8
Corporate and Other
Segment Reporting Information [Line Items]
Unaffiliated												426.8	405.9	418.7
Operating Income												(7.2)	(20.3)	(30.6)
Consolidated Depreciation and Amortization												19.7	24.1	24.9
Consolidated Assets		$ 2,362.2						$ 2,132.7				2,362.2	2,132.7	10,136.2	[3]
Payments to Acquire Property Plant and Equipment Including Captial Expenditures From Current Liabilities And Equity Method Investments	[2]											15.4	50.2	40.5
Eliminations
Segment Reporting Information [Line Items]
Unaffiliated												(426.5)	(397.6)	(413.6)
Unaffiliated | Gas Distribution Operations
Segment Reporting Information [Line Items]
Unaffiliated												2,818.2	3,068.7	3,593.6
Unaffiliated | Electric Operations
Segment Reporting Information [Line Items]
Unaffiliated												1,660.8	1,573.6	1,672.6
Unaffiliated | Corporate and Other
Segment Reporting Information [Line Items]
Unaffiliated												13.5	9.5	6.2
Intersegment | Gas Distribution Operations
Segment Reporting Information [Line Items]
Unaffiliated												12.4	0.4	0.3
Intersegment | Electric Operations
Segment Reporting Information [Line Items]
Unaffiliated												0.8	0.8	0.8
Intersegment | Corporate and Other
Segment Reporting Information [Line Items]
Unaffiliated												$ 413.3	$ 396.4	$ 412.5
[1]	First and second quarter results for 2016 differ from the results presented in the as-filed Form 10-Q for the respective periods as a result of the adoption of ASU 2016-09 in the third quarter of 2016. Refer to Note 2, "Recent Accounting Pronouncements," for additional information.
[2]	Amounts differ from those presented on the Statements of Consolidated Cash Flows primarily due to the inclusion of capital expenditures included in current liabilities and AFUDC Equity.
[3]	Corporate and Other in 2014 includes assets of Discontinued Operations. Refer to Note 3, "Discontinued Operations," for additional information.

Quarterly Financial Data (Sched

Quarterly Financial Data (Schedule Of Quarterly Financial Data) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended														12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	[1]	Mar. 31, 2016	[1]	Dec. 31, 2015		Sep. 30, 2015		Jun. 30, 2015		Mar. 31, 2015		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Quarterly Financial Data [Abstract]
Gross Revenues	$ 1,297	$ 861.3	$ 897.6		$ 1,436.6		$ 1,097.8		$ 817.2		$ 884.6		$ 1,852.2		$ 4,492.5	$ 4,651.8	$ 5,272.4
Operating Income	224.9	113.7	138.2		381.4		219.5		109.7		84.4		386.3		858.2	799.9	789.1
Income from Continuing Operations	88.8	23.7	29		186.6		64.4		14.8		(73.1)		192.5		328.1	198.6	256.2
Results from Discontinued Operations-net of taxes	0	3.5	(0.1)		0		(5)	[2]	(19.7)	[2]	45.4	[2]	82.8	[2]	(3.4)	(87.9)	(273.8)
Net Income	$ 88.8	$ 27.2	$ 28.9		$ 186.6		59.4		(4.9)		(27.7)		275.3		331.5	286.5	530
Net Income (Loss) attributable to NiSource							$ 59.4		$ (4.9)		$ (36.4)		$ 268.4		$ 331.5	$ 302.1	$ 530
Basic Earnings (Loss) Per Share, Continuing Operations	$ 0.28	$ 0.07	$ 0.09		$ 0.58		$ 0.20		$ 0.05		$ (0.23)		$ 0.61		$ 1.02	$ 0.63	$ 0.81
Basic Earnings (Loss) Per Share, Discontinued Operations	0	0.01	0		0		(0.01)		(0.07)		0.12		0.24		0.01	0.27	0.87
Basic Earnings (Loss) Per Share	0.28	0.08	0.09		0.58		0.19		(0.02)		(0.11)		0.85		1.03	0.90	1.68
Diluted Earnings (Loss) Per Share, Continuing Operations	0.27	0.07	0.09		0.58		0.20		0.05		(0.23)		0.61		1.01	0.63	0.81
Diluted Earnings (Loss) Per Share, Discontinued Operations	0	0.01	0		0		(0.01)		(0.07)		0.12		0.24		0.01	0.27	0.86
Diluted Earnings (Loss) Per Share	$ 0.27	$ 0.08	$ 0.09		$ 0.58		$ 0.19		$ (0.02)		$ (0.11)		$ 0.85		$ 1.02	$ 0.90	$ 1.67
[1]	First and second quarter results for 2016 differ from the results presented in the as-filed Form 10-Q for the respective periods as a result of the adoption of ASU 2016-09 in the third quarter of 2016. Refer to Note 2, "Recent Accounting Pronouncements," for additional information.
[2]	Includes the results of the former Columbia Pipeline Group segment.

Supplemental Cash Flow Infor114

Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Non-cash transactions:
Capital expenditures included in current liabilities	$ 125.3	$ 121.6	$ 127.4
Assets acquired under a capital lease	4	47.5	76.7
Schedule of interest and income taxes paid:
Cash paid for interest, net of interest capitalized amounts	337.8	390.4	429.3
Cash paid for income taxes	$ 8	$ 21.3	$ 19.4

Valuation And Qualifying Acc115

Valuation And Qualifying Accounts (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Reserve For Accounts Receivable [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning Balance		$ 20.3	$ 24.9	$ 23.4
Valuation Allowances and Reserves, Charged to Cost and Expense		19.7	22.5	21.8
Valuation Allowances and Reserves, Charged to Other Accounts	[1]	48.5	56.7	69.9
Deductions for Purposes for which Reserves were Created		65.2	83.8	90.2
Ending Balance		23.3	20.3	24.9
Reserve For Other Investments [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning Balance		3	3	3
Valuation Allowances and Reserves, Charged to Cost and Expense		0	0	0
Valuation Allowances and Reserves, Charged to Other Accounts	[1]	0	0	0
Deductions for Purposes for which Reserves were Created		0	0	0
Ending Balance		$ 3	$ 3	$ 3
[1]	Charged to Other Accounts reflects the deferral of bad debt expense to a regulatory asset.