DPL (DPL) 10-Q 8 May 17 2017 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2017	May 05, 2017
Entity Registrant Name	DPL INC
Entity Central Index Key	787,250
Document Type	10-Q
Document Period End Date	Mar. 31, 2017
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding		1
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	Q1
Entity Voluntary Filers	Yes
Entity Well-known Seasoned Issuer	No
THE DAYTON POWER AND LIGHT COMPANY [Member]
Entity Registrant Name	DAYTON POWER & LIGHT CO
Entity Central Index Key	27,430
Document Type	10-Q
Amendment Flag	false
Entity Current Reporting Status	Yes
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding		41,172,173
Entity Voluntary Filers	Yes
Entity Well-known Seasoned Issuer	No

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Revenues	$ 323.9	$ 364
Cost of revenues:
Fuel	54.1	66.9
Purchased power	102	121.9
Total cost of revenues	156.1	188.8
Gross margin	167.8	175.2
Operating expenses:
Operation and maintenance	86.3	88.5
Depreciation and amortization	28	33.4
General taxes	24.2	21
Impairment of Long-Lived Assets Held-for-use	66.4	0
Other	19.4	0.1
Other Operating Income (Expense), Net	(1.2)	0
Total operating expenses	223.1	143
Operating income / (loss)	(55.3)	32.2
Other income / (expense), net
Investment income	0	(0.1)
Interest expense	(26.9)	(26.3)
Charge for early retirement of debt	0	(2.6)
Other expense	(1)	(0.4)
Total other expense, net	(27.9)	(29.4)
Earnings / (loss) from continuing operations before income taxes	(83.2)	2.8
Income tax expense / (benefit) from continuing operations	(31.5)	0.6
Net income / (loss) from continuing operations	(51.7)	2.2
Income / (loss) from discontinued operations	0	(0.7)
Gain from disposal of discontinued operations	0	49.2
Income tax expense / (benefit) for discontinued operations	0	18.9
Discontinued operations	0	29.6
Net income / (loss)	(51.7)	31.8
THE DAYTON POWER AND LIGHT COMPANY [Member]
Revenues	311.1	349.2
Cost of revenues:
Fuel	50.1	62.9
Purchased power	100.8	121.3
Total cost of revenues	150.9	184.2
Gross margin	160.2	165
Operating expenses:
Operation and maintenance	82.6	86.1
Depreciation and amortization	23.5	34.3
General taxes	23.6	20.5
Impairment of Long-Lived Assets Held-for-use	66.3	0
Gain on termination of contract	0	(27.7)
Other	19.4	0.1
Total operating expenses	215.4	113.3
Operating income / (loss)	(55.2)	51.7
Other income / (expense), net
Investment income	0	(0.1)
Interest expense	(7.6)	(5.3)
Other expense	(0.9)	(0.2)
Total other expense, net	(8.5)	(5.6)
Earnings / (loss) from continuing operations before income taxes	(63.7)	46.1
Income tax expense / (benefit) from continuing operations	(21.9)	12.4
Net income / (loss)	(41.8)	33.7
Dividends on preferred stock	0	0.2
Income / (loss) attributable to common stock	$ (41.8)	$ 33.5

Condensed Consolidated Stateme3

Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Net income	$ (51.7)	$ 31.8
Available-for-sale securities activity:
Change in fair value of available-for-sale securities, net of income tax	0.2	0.2
Reclassification to earnings, net of income tax	(0.1)	(0.1)
Total change in fair value of available-for-sale securities	0.1	0.1
Derivative activity:
Change in derivative fair value, net of income tax	5.2	21.5
Reclassification of earnings, net of income tax	1	(8.2)
Total change in fair value of derivatives	6.2	13.3
Other Comprehensive (Income) Loss, Amortization Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, for Net Prior Service Cost (Credit), before Tax	(0.3)	0
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, for Net Gain (Loss), Net of Tax	(1.2)	0
Pension and postretirement activity:
Reclassification to earnings, net of income tax	0.8	0
Total change in unfunded pension obligation	(0.7)	0
Other comprehensive income / (loss)	5.6	13.4
Net comprehensive income / (loss)	(46.1)	45.2
THE DAYTON POWER AND LIGHT COMPANY [Member]
Net income	(41.8)	33.7
Available-for-sale securities activity:
Change in fair value of available-for-sale securities, net of income tax	0.2	0.2
Reclassification to earnings, net of income tax	(0.1)	(0.1)
Total change in fair value of available-for-sale securities	0.1	0.1
Derivative activity:
Change in derivative fair value, net of income tax	5.2	21.5
Reclassification of earnings, net of income tax	1	(8.4)
Total change in fair value of derivatives	6.2	13.1
Other Comprehensive (Income) Loss, Amortization Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, for Net Prior Service Cost (Credit), before Tax	(1.1)	0
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, for Net Gain (Loss), Net of Tax	(0.5)	0
Pension and postretirement activity:
Reclassification to earnings, net of income tax	2.5	0.3
Total change in unfunded pension obligation	0.9	0.3
Other comprehensive income / (loss)	7.2	13.5
Net comprehensive income / (loss)	$ (34.6)	$ 47.2

Condensed Consolidated Stateme4

Condensed Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Income tax (expense)/benefit on unrealized gains (losses) related to available-for-sale securities	$ 0	$ (0.1)
Income tax (expense) benefit on reclassification to earnings	0	0
Income tax (expense)/benefit on unrealized gains (losses) related to derivative activity	2.8	(11.6)
Income tax (expense)/benefit on reclassification of earnings related to derivative activity	(0.5)	4.8
Other Comprehensive (Income) Loss, Amortization Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, for Net Prior Service Cost (Credit), Tax	0.2	0
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Unamortized Gain (Loss) Arising During Period, Tax	0.7	0
Income tax (expense)/benefit on reclassification of earnings related to pension and postretirement activity	(0.5)	(0.1)
THE DAYTON POWER AND LIGHT COMPANY [Member]
Income tax (expense)/benefit on unrealized gains (losses) related to available-for-sale securities	0	(0.1)
Income tax (expense) benefit on reclassification to earnings	0	0
Income tax (expense)/benefit on unrealized gains (losses) related to derivative activity	(2.8)	(11.6)
Income tax (expense)/benefit on reclassification of earnings related to derivative activity	(0.5)	4.6
Other Comprehensive (Income) Loss, Amortization Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, for Net Prior Service Cost (Credit), Tax	0.6	0
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Unamortized Gain (Loss) Arising During Period, Tax	0.3	0
Income tax (expense)/benefit on reclassification of earnings related to pension and postretirement activity	$ (1.3)	$ (0.8)

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 54.3	$ 54.6
Restricted cash	8.4	29
Accounts receivable, net	101.4	135.1
Inventories	60.9	77.2
Taxes applicable to subsequent years	60.7	81
Regulatory assets, current	0.9	0.1
Other prepayments and current assets	33.7	31.8
Total current assets	320.3	408.8
Property, plant & equipment:
Property, plant & equipment	1,953.6	1,985.6
Less: Accumulated depreciation and amortization	(355.5)	(334.8)
Property, plant and equipment, net of depreciation	1,598.1	1,650.8
Construction work in process	102.5	116.4
Total net property, plant & equipment	1,700.6	1,767.2
Other non-current assets:
Regulatory assets, non-current	206	203.9
Intangible assets, net of amortization	23	22.7
Other deferred assets	14.3	16.6
Total other non-current assets	243.3	243.2
Total assets	2,264.2	2,419.2
Current liabilities:
Current portion of long-term debt	29.7	29.7
Accounts payable	78.8	113.9
Accrued taxes	159.5	185.1
Accrued interest	33.7	17.7
Security deposits	32.8	15.2
Regulatory liabilities, current	13.7	33.7
Insurance and claims costs	6.6	5.4
Other current liabilities	40.9	50.2
Total current liabilities	395.7	450.9
Non-current liabilities:
Long-term debt	1,822.3	1,828.7
Deferred taxes	252.4	252.4
Taxes payable	44.3	84.6
Regulatory liabilities, non-current	131.6	130.4
Pension, retiree and other benefits	100.6	101.6
Asset Retirement Obligations, Noncurrent	135.6	138.8
Other deferred credits	15.4	19.4
Total non-current liabilities	2,502.2	2,555.9
Commitments and contingencies
Common shareholder's equity:
Common stock	0	0
Other paid-in capital	2,233	2,233
Accumulated other comprehensive income	5.9	0.3
Retained earnings/ (deficit)	(2,872.6)	(2,820.9)
Total common shareholder's equity	(633.7)	(587.6)
Total liabilities and shareholder's equity	2,264.2	2,419.2
THE DAYTON POWER AND LIGHT COMPANY [Member]
Current assets:
Cash and cash equivalents	4.9	1.6
Restricted cash	8.4	29
Accounts receivable, net	110.6	134.6
Inventories	59.5	75.8
Taxes applicable to subsequent years	59.4	79.2
Regulatory assets, current	0.9	0.1
Other prepayments and current assets	33.4	32.4
Total current assets	277.1	352.7
Property, plant & equipment:
Property, plant & equipment	2,348.1	2,398.6
Less: Accumulated depreciation and amortization	(1,057.7)	(1,047.9)
Property, plant and equipment, net of depreciation	1,290.4	1,350.7
Construction work in process	80.4	89.9
Total net property, plant & equipment	1,370.8	1,440.6
Other non-current assets:
Regulatory assets, non-current	206	203.9
Intangible assets, net of amortization	23.2	23
Other deferred assets	12.8	14.9
Total other non-current assets	242	241.8
Total assets	1,889.9	2,035.1
Current liabilities:
Current portion of long-term debt	4.7	4.7
Short-term debt	0	5
Accounts payable	81	110.5
Accrued taxes	62.5	75.7
Accrued interest	0.9	2.1
Security deposits	32.8	15.2
Regulatory liabilities, current	13.7	33.7
Other current liabilities	39.5	48.3
Total current liabilities	235.1	295.2
Non-current liabilities:
Long-term debt	744	744.7
Deferred taxes	152.3	146.3
Taxes payable	44.5	84.1
Regulatory liabilities, non-current	131.6	130.4
Pension, retiree and other benefits	100.6	101.6
Asset Retirement Obligations, Noncurrent	132.3	135.2
Unamortized investment tax credit	17.2	17.7
Other deferred credits	13.5	17.6
Total non-current liabilities	1,336	1,377.6
Commitments and contingencies
Common shareholder's equity:
Common stock	0.4	0.4
Other paid-in capital	801.8	810.7
Accumulated other comprehensive income	(35.3)	(42.5)
Retained earnings/ (deficit)	(448.1)	(406.3)
Total common shareholder's equity	318.8	362.3
Total liabilities and shareholder's equity	$ 1,889.9	$ 2,035.1

Condensed Consolidated Balance6

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Mar. 31, 2017	Dec. 31, 2016
Common stock, shares authorized	1,500	1,500
Common stock, shares issued	1	1
Common stock, shares outstanding	1	1
THE DAYTON POWER AND LIGHT COMPANY [Member]
Common stock, shares authorized	250,000,000
Common stock, shares outstanding	41,172,173
Common stock, par value (in USD per share)	$ 0.01	$ 0.01

Condensed Consolidated Stateme7

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Cash flows from operating activities:
Net income	$ (51.7)	$ 31.8
Adjustments to reconcile net income / (loss) to net cash from operating activities:
Depreciation and amortization	28	33.4
Charge for early retirement of debt	0	2.6
Deferred income taxes	(4.7)	(9.2)
Impairment of Long-Lived Assets Held-for-use	66.4	0
Gain on sale of business	0	(49.2)
Gain (Loss) on Sale of Assets and Asset Impairment Charges	19.4	0.1
Changes in certain assets and liabilities:
Accounts receivable	38.1	35.8
Inventories	0.1	19
Prepaid taxes	0	0.2
Taxes applicable to subsequent years	20.2	21.6
Deferred regulatory costs, net	(23.8)	4.8
Accounts payable	(30.9)	(7.6)
Accrued taxes payable	(66)	(13.5)
Accrued interest payable	15.9	7.3
Security deposits	17.6	4.4
Increase (Decrease) Deferred Investment Tax Credit	(0.1)	(0.1)
Increase (Decrease) in Self Insurance Reserve	1.2	(0.4)
Increase (Decrease) in Pension and Postretirement Obligations	1.3	(4.5)
Other	(4.5)	9.1
Net cash provided by operating activities	26.5	83
Cash flows from investing activities:
Capital expenditures	(41.4)	(37.7)
Proceeds from sale of business	0	75.5
Insurance proceeds	1.2	0
Purchase of intangible assets	(0.1)	(0.1)
Decrease in restricted cash	20.6	1.3
Other investing activities, net	0.3	0.6
Net cash used in investing activities	(19.4)	39.6
Cash flows from financing activities:
Retirement of long-term debt	(7.4)	(75.4)
Net cash used in financing activities	(7.4)	(75.4)
Cash and cash equivalents:
Net change	(0.3)	47.2
Balance at beginning of period	54.6	32.4
Cash and cash equivalents at end of period	54.3	79.6
Supplemental cash flow information:
Interest paid, net of amounts capitalized	10.4	19.2
Non-cash financing and investing activities:
Accruals for capital expenditures	10.7	12.5
THE DAYTON POWER AND LIGHT COMPANY [Member]
Cash flows from operating activities:
Net income	(41.8)	33.7
Adjustments to reconcile net income / (loss) to net cash from operating activities:
Depreciation and amortization	23.5	34.3
Deferred income taxes	0.4	(1.8)
Impairment of Long-Lived Assets Held-for-use	66.3	0
Gain (Loss) on Sale of Assets and Asset Impairment Charges	19.4	0.1
Changes in certain assets and liabilities:
Accounts receivable	28.4	2.1
Inventories	0.1	19.1
Prepaid taxes	0	2.7
Taxes applicable to subsequent years	19.8	21.1
Deferred regulatory costs, net	(23.8)	4.8
Accounts payable	(24.6)	(9.8)
Accrued taxes payable	(52.7)	(28.2)
Accrued interest payable	(1.3)	(3.1)
Security deposits	17.6	4.4
Increase (Decrease) Deferred Investment Tax Credit	(0.5)	0
Increase (Decrease) in Pension and Postretirement Obligations	1.3	(4.5)
Other	(9.3)	8.5
Net cash provided by operating activities	22.8	83.4
Cash flows from investing activities:
Capital expenditures	(34.1)	(35.8)
Insurance proceeds	0	0.2
Purchase of intangible assets	(0.1)	(0.1)
Decrease in restricted cash	20.6	1.4
Other investing activities, net	0.2	0.5
Net cash used in investing activities	(13.4)	(33.8)
Cash flows from financing activities:
Retirement of long-term debt	(1.1)	0
Issuance of short-term debt - related party	30	5
Repayment of short-term debt - related party	(35)	(35)
Dividends paid on preferred stock	0	(0.2)
Net cash used in financing activities	(6.1)	(30.2)
Cash and cash equivalents:
Net change	3.3	19.4
Balance at beginning of period	1.6	5.4
Cash and cash equivalents at end of period	4.9	24.8
Supplemental cash flow information:
Interest paid, net of amounts capitalized	7.9	7.1
Non-cash financing and investing activities:
Accruals for capital expenditures	$ 8.7	$ 12.5

Overview and Summary of Signifi

Overview and Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2017
Significant Accounting Policies [Line Items]
Overview and Summary of Significant Accounting Policies	Overview and Summary of Significant Accounting Policies Description of Business DPL is a diversified regional energy company organized in 1985 under the laws of Ohio. DPL has two reportable segments: the Transmission and Distribution (T&D) segment and the Generation segment. See Note 12 – Business Segments for more information relating to these reportable segments. The terms “we,” “us,” “our” and “ours” are used to refer to DPL and its subsidiaries. DPL is an indirectly wholly-owned subsidiary of AES. DP&L is a public utility incorporated in 1911 under the laws of Ohio. Beginning in 2001, Ohio law gave Ohio consumers the right to choose the electric generation supplier from whom they purchase retail generation service; however, distribution and transmission retail services are still regulated. DP&L has the exclusive right to provide such distribution and transmission services to approximately 520,000 customers located in West Central Ohio. Additionally, DP&L offers retail SSO electric service to residential, commercial, industrial and governmental customers in a 6,000 square mile area of West Central Ohio. DP&L owns multiple coal-fired and peaking electric generating facilities as well as numerous transmission facilities, all of which are included in the financial statements at amortized cost. DP&L sources 100% of the generation for its SSO customers through a competitive bid process. Principal industries located in DP&L’s service territory include automotive, food processing, paper, plastic, manufacturing and defense. DP&L's distribution sales reflect the general economic conditions, seasonal weather patterns, retail competition in our service territory and the market price of electricity. DP&L sells all of its energy and capacity into the wholesale market. DPL’s other significant subsidiaries include AES Ohio Generation, which owns and operates peaking generating facilities from which it sells all of its energy and capacity into the wholesale market, and MVIC, our captive insurance company that provides insurance services to DPL and our subsidiaries. DPL owns all of the common stock of its subsidiaries. DPL also has a wholly-owned business trust, DPL Capital Trust II, formed for the purpose of issuing trust capital securities to investors. DP&L’s electric transmission and distribution businesses are subject to rate regulation by federal and state regulators while its generation business is deemed competitive under Ohio law. Accordingly, DP&L applies the accounting standards for regulated operations to its electric transmission and distribution businesses and records regulatory assets when incurred costs are expected to be recovered in future customer rates, and regulatory liabilities when current cost recoveries in customer rates relate to expected future costs. DPL and its subsidiaries employed 1,153 people as of March 31, 2017 , of which 1,145 were employed by DP&L . Approximately 62% of all DPL employees are under a collective bargaining agreement that expires on October 31, 2017 . Financial Statement Presentation DPL’s Condensed Consolidated Financial Statements include the accounts of DPL and its wholly-owned subsidiaries except for DPL Capital Trust II, which is not consolidated, consistent with the provisions of GAAP. DP&L has undivided ownership interests in five coal-fired generating facilities, various peaking generating facilities and numerous transmission facilities, all of which are included in the financial statements at amortized cost, which was adjusted to fair value at the date of the Merger for DPL . Operating revenues and expenses of these facilities are included on a pro rata basis in the corresponding lines in the Condensed Consolidated Statements of Operations. Certain immaterial amounts from prior periods have been reclassified to conform to the current period presentation. All material intercompany accounts and transactions are eliminated in consolidation. These financial statements have been prepared in accordance with GAAP for interim financial statements, the instructions of Form 10-Q and Regulation S-X. Accordingly, certain information and footnote disclosures normally included in the annual financial statements prepared in accordance with GAAP have been omitted from this interim report. Therefore, our interim financial statements in this report should be read along with the annual financial statements included in our Form 10-K for the fiscal year ended December 31, 2016 . In the opinion of our management, the Condensed Consolidated Financial Statements presented in this report contain all adjustments necessary to fairly state our financial position as of March 31, 2017 ; our results of operations for the three months ended March 31, 2017 and 2016 and our cash flows for the three months ended March 31, 2017 and 2016 . Unless otherwise noted, all adjustments are normal and recurring in nature. Due to various factors, including, but not limited to, seasonal weather variations, the timing of outages of EGUs, changes in economic conditions involving commodity prices and competition, and other factors, interim results for the three months ended March 31, 2017 may not be indicative of our results that will be realized for the full year ending December 31, 2017 . The preparation of financial statements in conformity with GAAP requires us to make estimates and judgments that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities, and the revenues and expenses of the periods reported. Actual results could differ from these estimates. Significant items subject to such estimates and judgments include: the carrying value of property, plant and equipment; unbilled revenues; the valuation of derivative instruments; the valuation of insurance and claims liabilities; the valuation of allowances for receivables and deferred income taxes; regulatory assets and liabilities; liabilities recorded for income tax exposures; litigation; contingencies; the valuation of AROs; and assets and liabilities related to employee benefits. Accounting for Taxes Collected from Customers and Remitted to Governmental Authorities DP&L collects certain excise taxes levied by state or local governments from its customers. These taxes are accounted for on a net basis and not included in revenue. The amounts of such taxes collected for the three months ended March 31, 2017 and 2016 were $12.5 million and $12.9 million, respectively. New Accounting Pronouncements The following table provides a brief description of recent accounting pronouncements that could have a material impact on our consolidated financial statements: Accounting Standard Description Date of Adoption Effect on the financial statements upon adoption New Accounting Standards Adopted 2016-09, Compensation - Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting The standard simplifies the following aspects of accounting for share-based payments awards: accounting for income taxes, classification of excess tax benefits on the statement of cash flows, forfeitures, statutory tax withholding requirements, classification of awards as either equity or liabilities and classification of employee taxes paid on statement of cash flows when an employer withholds shares for tax-withholding purposes. Transition method: The recognition of excess tax benefits and tax deficiencies arising from vesting or settlement were applied retrospectively. The elimination of the requirement that excess tax benefits be realized before they are recognized was adopted on a modified retrospective basis with a cumulative adjustment to the opening balance sheet. January 1, 2017 The primary effect of adoption was the recognition of excess tax benefits in our provision for income taxes in the period when the awards vest or are settled, rather than in paid-in-capital in the period when the excess tax benefits are realized. We will continue to estimate the number of awards that are expected to vest in our determination of the related periodic compensation cost. The adoption of this standard did not have a material impact on the consolidated financial statements. Accounting Standard Description Date of Adoption Effect on the financial statements upon adoption New Accounting Standards Issued But Not Yet Effective 2017-08, Receivables - Nonrefundable Fees and Other Costs (Subtopic 310-20): Premium Amortization on Purchased Callable Debt Securities This standard shortens the period of amortization of the premium on certain callable debt securities to the earliest call date. January 1, 2019. We are currently evaluating the impact of adopting the standard on our consolidated financial statements. 2017-07, Compensation—Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost The standard provides guidance on the presentation of net benefit cost in an employer’s income statement and on the components eligible for capitalization. It requires that an employer report the service cost component in the same line item(s) as other employee compensation costs arising from services rendered during the period, and report the other components of net benefit cost separately from the service cost component and outside a subtotal of operating income. Only the service cost component will be eligible for capitalization. January 1, 2018. Early adoption is permitted. We are currently evaluating the impact of adopting the standard on our consolidated financial statements. 2017-01, Business Combinations (Topic 805): Clarifying the Definition of a Business This standard provides guidance to assist the entities with evaluating when a set of transferred assets and activities is a business. January 1, 2018. Early adoption is permitted We are currently evaluating the impact of adopting the standard on our consolidated financial statements. 2016-18, Statement of Cash Flows (Topic 320): Restricted Cash (a consensus of the FASB Emerging Issues Task Force) This standard requires that a statement of cash flows explain the change during the period in the total of cash, cash equivalents, and amounts generally described as restricted cash or restricted cash equivalents. Therefore, amounts generally described as restricted cash and restricted cash equivalents should be included with cash and cash equivalents when reconciling the beginning-of-period and end-of-period total amounts shown on the statement of cash flows. January 1, 2018. Early adoption is permitted We are currently evaluating the impact of adopting the standard on our consolidated financial statements. 2016-16, Income Taxes (Topic 740): Intra-Entity Transfers of Assets Other Than Inventory This standard requires that an entity recognizes the income tax consequences of an intra-entity transfer of an asset other than inventory when the transfer occurs. January 1, 2018. Early adoption is permitted. We are currently evaluating the impact of adopting the standard on our consolidated financial statements. 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Receipts and Cash Payments (a consensus of the Emerging Issues Task Force) This standard provides specific guidance on how certain cash transactions are presented and classified in the statement of cash flows. January 1, 2018. Early adoption is permitted. We are currently evaluating the impact of adopting the standard on our consolidated financial statements but do not anticipate a material impact. 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments This standard updates the impairment model for financial assets measured at amortized cost to an expected loss model rather than an incurred loss model. It also allows for the presentation of credit losses on available-for-sale debt securities as an allowance rather than a write down. January 1, 2020. Early adoption is permitted only as of January 1, 2019. We are currently evaluating the impact of adopting the standard on our consolidated financial statements. 2016-02, Leases (Topic 842) The standard creates Topic 842, Leases which supersedes Topic 840, Leases, and introduces a lessee model that brings substantially all leases onto the balance sheet while retaining most of the principles of the existing lessor model in U.S. GAAP and aligning many of those principles with ASC 606, Revenue from Contracts with Customers. January 1, 2019. Early adoption is permitted. We are currently evaluating the impact of adopting the standard on our consolidated financial statements. Accounting Standard Description Date of Adoption Effect on the financial statements upon adoption 2014-09, 2015-14, 2016-08, 2016-10, 2016-12, 2016-20, 2017-05 Revenue from Contracts with Customers (Topic 606) See discussion of the ASUs below. January 1, 2018. Earlier application is permitted only as of January 1, 2017. We will adopt the standard on January 1, 2018; see below for the evaluation of the impact of its adoption on the consolidated financial statements. ASU 2014-09 and its subsequent corresponding updates provide the principles an entity must apply to measure and recognize revenue. The core principle is that an entity shall recognize revenue to depict the transfer of promised 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. Amendments to the standard were issued that provide further clarification of the principle and to provide certain transition expedients. The standard will replace most existing revenue recognition guidance in GAAP, including the guidance on recognizing other income upon the sale or transfer of nonfinancial assets (including in-substance real estate). The standard requires retrospective application and allows either a full retrospective adoption in which all of the periods are presented under the new standard or a modified retrospective approach in which the cumulative effect of initially applying the guidance is recognized at the date of initial application. We are currently working towards adopting the standard using the full retrospective method. However, we will continue to assess this conclusion which is dependent on the final impact to the financial statements. In 2016, we established a cross-functional implementation team and are in the process of evaluating changes to our business processes, systems and controls to support recognition and disclosure under the new standard. Given the complexity and diversity of our non-regulated arrangements, we are assessing the standard on a contract by contract basis and have completed more than half of the total expected effort. Through this assessment, we have identified certain key issues that we are continuing to evaluate in order to complete our assessment of the full population of contracts and be able to assess the overall impact to the financial statements. These issues include: the application of the practical expedient for measuring progress toward satisfaction of a performance obligation, when variable quantities would be considered variable consideration versus an option to acquire additional goods and services, and how to measure progress toward completion for a performance obligation that is a bundle. We are continuing to work with various non-authoritative industry groups, and monitoring the FASB and Transition Resource Group activity, as we finalize our accounting policy on these and other industry specific interpretative issues which is expected in 2017. We are currently evaluating certain contracts along with our tariff revenue, capacity agreements with PJM and wholesale agreements with PJM. We expect additional contracts to be executed during 2017 that will require assessment under the new standard.
THE DAYTON POWER AND LIGHT COMPANY [Member]
Significant Accounting Policies [Line Items]
Overview and Summary of Significant Accounting Policies	Overview and Summary of Significant Accounting Policies Description of Business DP&L is a public utility incorporated in 1911 under the laws of Ohio. Beginning in 2001, Ohio law gave Ohio consumers the right to choose the electric generation supplier from whom they purchase retail generation service; however, distribution and transmission retail services are still regulated. DP&L has the exclusive right to provide such distribution and transmission services to approximately 520,000 customers located in West Central Ohio. Additionally, DP&L offers retail SSO electric service to residential, commercial, industrial and governmental customers in a 6,000 square mile area of West Central Ohio. DP&L owns multiple coal-fired and peaking electric generating facilities as well as numerous transmission facilities, all of which are included in the financial statements at amortized cost. DP&L sources 100% of the generation for its SSO customers through a competitive bid process. Principal industries located in DP&L’s service territory include automotive, food processing, paper, plastic, manufacturing and defense. DP&L's distribution sales reflect the general economic conditions, seasonal weather patterns, retail competition in our service territory and the market price of electricity. DP&L sells all of its energy and capacity into the wholesale market. DP&L is a subsidiary of DPL . DP&L has two reportable segments: the Transmission and Distribution (T&D) segment and the Generation segment. See Note 13 – Business Segments for more information relating to these reportable segments. DP&L’s electric transmission and distribution businesses are subject to rate regulation by federal and state regulators while its generation business is deemed competitive under Ohio law. Accordingly, DP&L applies the accounting standards for regulated operations to its electric transmission and distribution businesses and records regulatory assets when incurred costs are expected to be recovered in future customer rates, and regulatory liabilities when current cost recoveries in customer rates relate to expected future costs. DP&L employed 1,145 people as of March 31, 2017 . Approximately 62% of all employees are under a collective bargaining agreement which expires on October 31, 2017 . Financial Statement Presentation DP&L does not have any subsidiaries. DP&L has undivided ownership interests in five coal-fired generating facilities, peaking electric generating facilities and numerous transmission facilities, all of which are included in the financial statements at amortized cost. Operating revenues and expenses of these facilities are included on a pro rata basis in the corresponding lines in the Condensed Statements of Operations. Certain immaterial amounts from prior periods have been reclassified to conform to the current period presentation. These financial statements have been prepared in accordance with GAAP for interim financial statements, the instructions of Form 10-Q and Regulation S-X. Accordingly, certain information and footnote disclosures normally included in the annual financial statements prepared in accordance with GAAP have been omitted from this interim report. Therefore, our interim financial statements in this report should be read along with the annual financial statements included in our Form 10-K for the fiscal year ended December 31, 2016 . In the opinion of our management, the Condensed Financial Statements presented in this report contain all adjustments necessary to fairly state our financial position as of March 31, 2017 ; our results of operations for the three months ended March 31, 2017 and 2016 and our cash flows for the three months ended March 31, 2017 and 2016 . Unless otherwise noted, all adjustments are normal and recurring in nature. Due to various factors, including, but not limited to, seasonal weather variations, the timing of outages of EGUs, changes in economic conditions involving commodity prices and competition, and other factors, interim results for the three months ended March 31, 2017 may not be indicative of our results that will be realized for the full year ending December 31, 2017 . The preparation of financial statements in conformity with GAAP requires us to make estimates and judgments that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities, and the revenues and expenses of the periods reported. Actual results could differ from these estimates. Significant items subject to such estimates and judgments include: the carrying value of property, plant and equipment; unbilled revenues; the valuation of derivative instruments; the valuation of insurance and claims liabilities; the valuation of allowances for receivables and deferred income taxes; regulatory assets and liabilities; liabilities recorded for income tax exposures; litigation; contingencies; the valuation of AROs; and assets and liabilities related to employee benefits. Accounting for Taxes Collected from Customers and Remitted to Governmental Authorities DP&L collects certain excise taxes levied by state or local governments from its customers. These taxes are accounted for on a net basis and not included in revenue. The amounts of such taxes collected for the three months ended March 31, 2017 and 2016 were $12.5 million and $12.9 million, respectively. New Accounting Pronouncements The following table provides a brief description of recent accounting pronouncements that could have a material impact on our financial statements: Accounting Standard Description Date of Adoption Effect on the financial statements upon adoption New Accounting Standards Adopted 2016-09, Compensation - Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting The standard simplifies the following aspects of accounting for share-based payments awards: accounting for income taxes, classification of excess tax benefits on the statement of cash flows, forfeitures, statutory tax withholding requirements, classification of awards as either equity or liabilities and classification of employee taxes paid on statement of cash flows when an employer withholds shares for tax-withholding purposes. Transition method: The recognition of excess tax benefits and tax deficiencies arising from vesting or settlement were applied retrospectively. The elimination of the requirement that excess tax benefits be realized before they are recognized was adopted on a modified retrospective basis with a cumulative adjustment to the opening balance sheet. January 1, 2017 The primary effect of adoption was the recognition of excess tax benefits in our provision for income taxes in the period when the awards vest or are settled, rather than in paid-in-capital in the period when the excess tax benefits are realized. We will continue to estimate the number of awards that are expected to vest in our determination of the related periodic compensation cost. The adoption of this standard did not have a material impact on the financial statements. New Accounting Standards Issued But Not Yet Effective 2017-08, Receivables - Nonrefundable Fees and Other Costs (Subtopic 310-20): Premium Amortization on Purchased Callable Debt Securities This standard shortens the period of amortization of the premium on certain callable debt securities to the earliest call date. January 1, 2019. We are currently evaluating the impact of adopting the standard on our financial statements. 2017-07, Compensation—Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost The standard provides guidance on the presentation of net benefit cost in an employer’s income statement and on the components eligible for capitalization. It requires that an employer report the service cost component in the same line item(s) as other employee compensation costs arising from services rendered during the period, and report the other components of net benefit cost separately from the service cost component and outside a subtotal of operating income. Only the service cost component will be eligible for capitalization. January 1, 2018. Early adoption is permitted. We are currently evaluating the impact of adopting the standard on our financial statements. 2017-01, Business Combinations (Topic 805): Clarifying the Definition of a Business This standard provides guidance to assist the entities with evaluating when a set of transferred assets and activities is a business. January 1, 2018. Early adoption is permitted We are currently evaluating the impact of adopting the standard on our financial statements. Accounting Standard Description Date of Adoption Effect on the financial statements upon adoption 2016-18, Statement of Cash Flows (Topic 320): Restricted Cash (a consensus of the FASB Emerging Issues Task Force) This standard requires that a statement of cash flows explain the change during the period in the total of cash, cash equivalents, and amounts generally described as restricted cash or restricted cash equivalents. Therefore, amounts generally described as restricted cash and restricted cash equivalents should be included with cash and cash equivalents when reconciling the beginning-of-period and end-of-period total amounts shown on the statement of cash flows. January 1, 2018. Early adoption is permitted We are currently evaluating the impact of adopting the standard on our financial statements. 2016-16, Income Taxes (Topic 740): Intra-Entity Transfers of Assets Other Than Inventory This standard requires that an entity recognizes the income tax consequences of an intra-entity transfer of an asset other than inventory when the transfer occurs. January 1, 2018. Early adoption is permitted. We are currently evaluating the impact of adopting the standard on our financial statements. 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Receipts and Cash Payments (a consensus of the Emerging Issues Task Force) This standard provides specific guidance on how certain cash transactions are presented and classified in the statement of cash flows. January 1, 2018. Early adoption is permitted. We are currently evaluating the impact of adopting the standard on our financial statements but do not anticipate a material impact. 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments This standard updates the impairment model for financial assets measured at amortized cost to an expected loss model rather than an incurred loss model. It also allows for the presentation of credit losses on available-for-sale debt securities as an allowance rather than a write down. January 1, 2020. Early adoption is permitted only as of January 1, 2019. We are currently evaluating the impact of adopting the standard on our financial statements. 2016-02, Leases (Topic 842) The standard creates Topic 842, Leases which supersedes Topic 840, Leases, and introduces a lessee model that brings substantially all leases onto the balance sheet while retaining most of the principles of the existing lessor model in U.S. GAAP and aligning many of those principles with ASC 606, Revenue from Contracts with Customers. January 1, 2019. Early adoption is permitted. We are currently evaluating the impact of adopting the standard on our financial statements. 2014-09, 2015-14, 2016-08, 2016-10, 2016-12, 2016-20, 2017-05 Revenue from Contracts with Customers (Topic 606) See discussion of the ASUs below. January 1, 2018. Earlier application is permitted only as of January 1, 2017. We will adopt the standard on January 1, 2018; see below for the evaluation of the impact of its adoption on the financial statements. ASU 2014-09 and its subsequent corresponding updates provide the principles an entity must apply to measure and recognize revenue. The core principle is that an entity shall recognize revenue to depict the transfer of promised 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. Amendments to the standard were issued that provide further clarification of the principle and to provide certain transition expedients. The standard will replace most existing revenue recognition guidance in GAAP, including the guidance on recognizing other income upon the sale or transfer of nonfinancial assets (including in-substance real estate). The standard requires retrospective application and allows either a full retrospective adoption in which all of the periods are presented under the new standard or a modified retrospective approach in which the cumulative effect of initially applying the guidance is recognized at the date of initial application. We are currently working towards adopting the standard using the full retrospective method. However, we will continue to assess this conclusion which is dependent on the final impact to the financial statements. In 2016, we established a cross-functional implementation team and are in the process of evaluating changes to our business processes, systems and controls to support recognition and disclosure under the new standard. Given the complexity and diversity of our non-regulated arrangements, we are assessing the standard on a contract by contract basis and have completed more than half of the total expected effort. Through this assessment, we have identified certain key issues that we are continuing to evaluate in order to complete our assessment of the full population of contracts and be able to assess the overall impact to the financial statements. These issues include: the application of the practical expedient for measuring progress toward satisfaction of a performance obligation, when variable quantities would be considered variable consideration versus an option to acquire additional goods and services, and how to measure progress toward completion for a performance obligation that is a bundle. We are continuing to work with various non-authoritative industry groups, and monitoring the FASB and Transition Resource Group activity, as we finalize our accounting policy on these and other industry specific interpretative issues which is expected in 2017. We are currently evaluating certain contracts along with our tariff revenue, capacity agreements with PJM and wholesale agreements with PJM. We expect additional contracts to be executed during 2017 that will require assessment under the new standard.

Supplemental Financial Informat

Supplemental Financial Information	3 Months Ended
	Mar. 31, 2017
Supplemental Financial Information [Line Items]
Supplemental Financial Information	Supplemental Financial Information Accounts receivable and Inventories are as follows at March 31, 2017 and December 31, 2016 : March 31, December 31, $ in millions 2017 2016 Accounts receivable, net: Unbilled revenue $ 14.7 $ 43.0 Customer receivables 68.4 73.9 Amounts due from partners in jointly owned plants 6.6 12.7 Other 12.7 6.7 Provision for uncollectible accounts (1.0 ) (1.2 ) Total accounts receivable, net $ 101.4 $ 135.1 Inventories, at average cost: Fuel and limestone $ 38.8 $ 38.9 Plant materials and supplies 20.6 36.6 Other 1.5 1.7 Total inventories, at average cost $ 60.9 $ 77.2 Accumulated Other Comprehensive Income / (Loss) The amounts reclassified out of Accumulated Other Comprehensive Income / (Loss) by component during the three months ended March 31, 2017 and 2016 are as follows: Details about Accumulated Other Comprehensive Income / (Loss) components Affected line item in the Condensed Consolidated Statements of Operations Three months ended March 31, $ in millions 2017 2016 Gains and losses on Available-for-sale securities activity (Note 5): Other income $ (0.1 ) $ (0.1 ) Gains and losses on cash flow hedges (Note 6): Interest expense (0.3 ) (0.2 ) Revenue (1.5 ) (17.2 ) Purchased power 3.3 4.4 Total before income taxes 1.5 (13.0 ) Tax expense / (benefit) (0.5 ) 4.8 Net of income taxes 1.0 (8.2 ) Amortization of defined benefit pension items (Note 9): Operation and maintenance 1.3 0.1 Tax benefit (0.5 ) (0.1 ) Net of income taxes 0.8 — Total reclassifications for the period, net of income taxes $ 1.7 $ (8.3 ) The changes in the components of Accumulated Other Comprehensive Income / (Loss) during the three months ended March 31, 2017 are as follows: $ in millions Gains / (losses) on available-for-sale securities Gains / (losses) on cash flow hedges Change in unfunded pension obligation Total Balance January 1, 2017 $ 0.6 $ 13.1 $ (13.4 ) $ 0.3 Other comprehensive income / (loss) before reclassifications 0.2 5.2 (1.5 ) 3.9 Amounts reclassified from accumulated other comprehensive income / (loss) (0.1 ) 1.0 0.8 1.7 Net current period other comprehensive income / (loss) 0.1 6.2 (0.7 ) 5.6 Balance March 31, 2017 $ 0.7 $ 19.3 $ (14.1 ) $ 5.9
THE DAYTON POWER AND LIGHT COMPANY [Member]
Supplemental Financial Information [Line Items]
Supplemental Financial Information	Supplemental Financial Information Accounts receivable and Inventories are as follows at March 31, 2017 and December 31, 2016 : March 31, December 31, $ in millions 2017 2016 Accounts receivable, net: Unbilled revenue $ 14.7 $ 43.0 Customer receivables 65.2 71.2 Amounts due from partners in jointly owned plants 6.6 12.7 Amounts due from affiliates 14.8 2.9 Other 10.3 6.0 Provision for uncollectible accounts (1.0 ) (1.2 ) Total accounts receivable, net $ 110.6 $ 134.6 Inventories, at average cost: Fuel and limestone $ 38.8 $ 38.8 Plant materials and supplies 19.2 35.3 Other 1.5 1.7 Total inventories, at average cost $ 59.5 $ 75.8 Accumulated Other Comprehensive Income / (Loss) The amounts reclassified out of Accumulated Other Comprehensive Income / (Loss) by component during the three months ended March 31, 2017 and 2016 are as follows: Details about Accumulated Other Comprehensive Income / (Loss) components Affected line item in the Condensed Statements of Operations Three months ended March 31, $ in millions 2017 2016 Gains and losses on Available-for-sale securities activity (Note 5): Other income $ (0.1 ) $ (0.1 ) Gains and losses on cash flow hedges (Note 6): Interest expense (0.3 ) (0.3 ) Revenue (1.5 ) (17.1 ) Purchased power 3.3 4.4 Total before income taxes 1.5 (13.0 ) Tax expense / (benefit) (0.5 ) 4.6 Net of income taxes 1.0 (8.4 ) Amortization of defined benefit pension items (Note 9): Operation and maintenance 3.8 1.1 Tax benefit (1.3 ) (0.8 ) Net of income taxes 2.5 0.3 Total reclassifications for the period, net of income taxes $ 3.4 $ (8.2 ) The changes in the components of Accumulated Other Comprehensive Income / (Loss) during the three months ended March 31, 2017 are as follows: $ in millions Gains / (losses) on available-for-sale securities Gains / (losses) on cash flow hedges Change in unfunded pension obligation Total Balance January 1, 2017 $ 0.7 $ (2.7 ) $ (40.5 ) $ (42.5 ) Other comprehensive income / (loss) before reclassifications 0.2 5.2 (1.6 ) 3.8 Amounts reclassified from accumulated other comprehensive income / (loss) (0.1 ) 1.0 2.5 3.4 Net current period other comprehensive income 0.1 6.2 0.9 7.2 Balance March 31, 2017 $ 0.8 $ 3.5 $ (39.6 ) $ (35.3 )

Regulatory Matters (Notes)

Regulatory Matters (Notes)	3 Months Ended
	Mar. 31, 2017
Schedule of Regulatory Assets and Liabilities [Text Block]	Regulatory Matters DP&L originally filed its ESP 3 seeking an effective date of January 1, 2017. On October 11, 2016, DP&L amended the application requesting to collect $145.0 million per year for seven years named the Distribution Modernization Rider ("DMR"). This plan established the terms and conditions for DP&L’s SSO to customers that do not choose a competitive retail electric supplier, and recommended including renewable energy attributes as part of the product that is competitively bid. DP&L sought recovery of approximately $10.5 million of regulatory assets, and proposed a new Distribution Investment Rider to allow DP&L to recover costs associated with future distribution equipment and infrastructure needs. Additionally, the plan established new riders set initially at zero , related to energy reductions from DP&L’s energy efficiency programs, and certain environmental liabilities. On January 30, 2017, DP&L , in conjunction with various intervening parties, filed a settlement in the ESP 3 case. On March 13, 2017, DP&L , in conjunction with various intervening parties and the staff of the PUCO, filed an Amended Stipulation in the ESP 3 case, which is subject to PUCO approval. The intervening parties agreed to a six-year settlement that provides a framework for energy rates and defines components which include, but are not limited to, the following: • Bypassable standard offer energy rates for DP&L’s customers based on competitive bid auctions; • The establishment of a three-year non-bypassable DMR designed to collect $105.0 million in revenue per year to pay debt obligations at DPL and DP&L and position DP&L to modernize and/or maintain its transmission and distribution infrastructure. With PUCO approval, DP&L may have the option of extending the duration of the DMR for an additional two years; • The establishment of a non-bypassable Distribution Investment Rider, set initially at zero, to recover incremental distribution capital investments; • The establishment of a Smart Grid Rider, set initially at zero, to recover costs of future grid modernization; • A commitment by us to separate DP&L’s generation assets from its transmission and distribution assets (if approved by FERC) within 180 days after receipt of a PUCO order; • A commitment to commence a sale process to sell our ownership interests in the Zimmer, Miami Fort and Conesville coal-fired generation plants; and • Restrictions on DPL making dividend or tax sharing payments, and various other riders and competitive retail market enhancements. A hearing was held in April 2017 and a final decision by the PUCO is expected at the end of the second quarter or early in the third quarter of 2017. There can be no assurance that the Amended ESP 3 stipulation will be approved as filed or on a timely basis, and if the Amended ESP 3 stipulation is not approved on a timely basis or if the final ESP provides for terms that are more adverse than those submitted in DP&L's Amended stipulation, our results of operations, financial condition and cash flows and DPL's ability to meet long-term obligations, in the periods beyond twelve months from the date of this report, could be materially impacted. In connection with any sale or closure of our generation plants as contemplated by the ESP 3 settlement or otherwise, DPL and DP&L would expect to incur certain cash and non-cash charges, some or all of which could be material to the business and financial condition of DPL and DP&L . DP&L’s ESP 2 had been approved by the PUCO for the years 2014 - 2016, and permitted DP&L to collect a non-bypassable service stability rider equal to $110.0 million per year for each of those years and required DP&L to conduct competitive bid auctions to procure generation supply for SSO service. The Ohio Supreme Court in a June 2016 opinion stated that the PUCO’s approval of the ESP was reversed. In view of that reversal, DP&L filed a motion to withdraw its ESP 2 and implement rates consistent with those in effect prior to 2014. The PUCO approved DP&L’s withdrawal of ESP 2 and implementation plans. Those rates will be in effect until rates consistent with DP&L’s pending ESP 3 filing are approved and effective. In February 2017, several parties appealed the PUCO orders that approved both the withdrawal and the implementation plans to the Ohio Supreme Court. Those appeals are pending and the outcome and potential financial impact of those appeals cannot be determined at this time.
Subsidiaries [Member]
Schedule of Regulatory Assets and Liabilities [Text Block]	Regulatory Matters DP&L originally filed its ESP 3 seeking an effective date of January 1, 2017. On October 11, 2016, DP&L amended the application requesting to collect $145.0 million per year for seven years named the Distribution Modernization Rider ("DMR"). This plan established the terms and conditions for DP&L’s SSO to customers that do not choose a competitive retail electric supplier, and recommended including renewable energy attributes as part of the product that is competitively bid. DP&L sought recovery of approximately $10.5 million of regulatory assets, and proposed a new Distribution Investment Rider to allow DP&L to recover costs associated with future distribution equipment and infrastructure needs. Additionally, the plan established new riders set initially at zero , related to energy reductions from DP&L’s energy efficiency programs, and certain environmental liabilities. On January 30, 2017, DP&L , in conjunction with various intervening parties, filed a settlement in the ESP 3 case. On March 13, 2017, DP&L , in conjunction with various intervening parties and the staff of the PUCO, filed an Amended Stipulation in the ESP 3 case, which is subject to PUCO approval. The intervening parties agreed to a six-year settlement that provides a framework for energy rates and defines components which include, but are not limited to, the following: • Bypassable standard offer energy rates for DP&L’s customers based on competitive bid auctions; • The establishment of a three-year non-bypassable DMR designed to collect $105.0 million in revenue per year to pay debt obligations at DPL and DP&L and position DP&L to modernize and/or maintain its transmission and distribution infrastructure. With PUCO approval, DP&L may have the option of extending the duration of the DMR for an additional two years; • The establishment of a non-bypassable Distribution Investment Rider, set initially at zero, to recover incremental distribution capital investments; • The establishment of a Smart Grid Rider, set initially at zero, to recover costs of future grid modernization; • A commitment by us to separate DP&L’s generation assets from its transmission and distribution assets (if approved by FERC) within 180 days after receipt of a PUCO order; • A commitment to commence a sale process to sell our ownership interests in the Zimmer, Miami Fort and Conesville coal-fired generation plants; and • Restrictions on DPL making dividend or tax sharing payments, and various other riders and competitive retail market enhancements. A hearing was held in April 2017 and a final decision by the PUCO is expected at the end of the second quarter or early in the third quarter of 2017. There can be no assurance that the Amended ESP 3 stipulation will be approved as filed or on a timely basis, and if the Amended ESP 3 stipulation is not approved on a timely basis or if the final ESP provides for terms that are more adverse than those submitted in DP&L's Amended stipulation, our results of operations, financial condition and cash flows and DPL's ability to meet long-term obligations, in the periods beyond twelve months from the date of this report, could be materially impacted. In connection with any sale or closure of our generation plants as contemplated by the ESP 3 settlement or otherwise, DPL and DP&L would expect to incur certain cash and non-cash charges, some or all of which could be material to the business and financial condition of DPL and DP&L . DP&L’s ESP 2 had been approved by the PUCO for the years 2014 - 2016, and permitted DP&L to collect a non-bypassable service stability rider equal to $110.0 million per year for each of those years and required DP&L to conduct competitive bid auctions to procure generation supply for SSO service. The Ohio Supreme Court in a June 2016 opinion stated that the PUCO’s approval of the ESP was reversed. In view of that reversal, DP&L filed a motion to withdraw its ESP 2 and implement rates consistent with those in effect prior to 2014. The PUCO approved DP&L’s withdrawal of ESP 2 and implementation plans. Those rates will be in effect until rates consistent with DP&L’s pending ESP 3 filing are approved and effective. In February 2017, several parties appealed the PUCO orders that approved both the withdrawal and the implementation plans to the Ohio Supreme Court. Those appeals are pending and the outcome and potential financial impact of those appeals cannot be determined at this time.

Property, Plant and Equipment (

Property, Plant and Equipment (Notes)	3 Months Ended
	Mar. 31, 2017
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment Disclosure [Text Block]	Property, Plant and Equipment DP&L and certain other Ohio utilities have undivided ownership interests in five coal-fired electric generating facilities and numerous transmission facilities. Certain expenses, primarily fuel costs for the generating units, are allocated to the owners based on their energy usage. The remaining expenses, investments in fuel inventory, plant materials and operating supplies, and capital additions are allocated to the owners in accordance with their respective ownership interests. At March 31, 2017 , DP&L had $11.0 million of construction work in process at such facilities. DP&L’s share of the operations of such facilities is included within the corresponding line in the Condensed Consolidated Statements of Operations, and DP&L’s share of the investment in the facilities is included within Total net property, plant and equipment in the Condensed Consolidated Balance Sheets. Each joint owner provides their own financing for their share of the operations and capital expenditures of the jointly-owned station. Coal-fired facilities DP&L’s undivided ownership interest in such facilities at March 31, 2017 , is as follows: DP&L Share DPL Carrying Value Ownership (%) Summer Production Capacity (MW) Gross Plant In Service ($ in millions) Accumulated Depreciation ($ in millions) Construction Work in Process ($ in millions) Jointly-owned production units Conesville - Unit 4 16.5 129 $ — $ — $ — Killen - Unit 2 67.0 402 7.0 1.0 1.0 Miami Fort - Units 7 and 8 36.0 368 28.0 1.0 5.0 Stuart - Units 1 through 4 35.0 808 1.0 1.0 — Zimmer - Unit 1 28.1 371 12.0 1.0 5.0 Transmission (at varying percentages) 43.0 11.0 — Total 2,078 $ 91.0 $ 15.0 $ 11.0 Each of the above generating units has SCR and FGD equipment installed. On January 10, 2017, a high pressure feedwater heater shell failed on Unit 1 at the J.M. Stuart station. As a result, $6.4 million of net book value was written off, resulting in a $3.2 million loss on disposal, net of insurance recoveries. As the damage assessment process is currently ongoing, we cannot determine the impact to operations or capacity at this time. On March 17, 2017, the Board of Directors of DP&L approved the retirement of the DP&L operated and co-owned Stuart Station coal-fired and diesel-fired generating units and the Killen Station coal-fired generating unit and combustion turbine on or before June 1, 2018, and DP&L agreed with the co-owners of these facilities to proceed with this plan of retirement. On April 21, 2017, DP&L and AES Ohio Generation entered into an agreement for the sale of DP&L’s undivided interests in Zimmer and Miami Fort, for $50.0 million in cash and the assumption of certain liabilities, including environmental. The purchase price is subject to adjustment at closing based on the amount of certain inventories, pre-paid amounts, employment benefits, insurance premiums, property taxes and other costs. The sale is subject to approval by the FERC and is expected to close in the third quarter of 2017. AROs We recognize AROs in accordance with GAAP which requires legal obligations associated with the retirement of long-lived assets to be recognized at their fair value at the time those obligations are incurred. Upon initial recognition of a legal liability, costs are capitalized as part of the related long-lived asset and depreciated over the useful life of the related asset. Our legal obligations are associated with the retirement of our long-lived assets, consisting primarily of river intake and discharge structures, coal unloading facilities, loading docks, ice breakers and ash disposal facilities. Estimating the amount and timing of future expenditures of this type requires significant judgment. Management routinely updates these estimates as additional information becomes available. Changes in the Liability for Generation AROs $ in millions Balance January 1, 2017 $ 138.8 Revisions to cash flow and timing estimates (4.4 ) Accretion expense 1.1 Settlements 0.1 Balance March 31, 2017 $ 135.6 See Note 5 – Fair Value for further discussion on ARO additions.
Subsidiaries [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment Disclosure [Text Block]	Property, Plant and Equipment DP&L and certain other Ohio utilities have undivided ownership interests in five coal-fired electric generating facilities and numerous transmission facilities. Certain expenses, primarily fuel costs for the generating units, are allocated to the owners based on their energy usage. The remaining expenses, investments in fuel inventory, plant materials and operating supplies, and capital additions are allocated to the owners in accordance with their respective ownership interests. At March 31, 2017 , DP&L had $11.0 million of construction work in process at such facilities. DP&L’s share of the operations of such facilities is included within the corresponding line in the Condensed Statements of Operations, and DP&L’s share of the investment in the facilities is included within Total net property, plant and equipment in the Condensed Balance Sheets. Each joint owner provides their own financing for their share of the operations and capital expenditures of the jointly-owned station. Coal-fired facilities DP&L’s undivided ownership interest in such facilities at March 31, 2017 , is as follows: DP&L Share DP&L Carrying Value Ownership % Summer Production Capacity (MW) Gross Plant In Service ($ in millions) Accumulated Depreciation ($ in millions) Construction Work in Process ($ in millions) Jointly-owned production units Conesville - Unit 4 16.5 129 $ — $ — $ — Killen - Unit 2 67.0 402 7.0 1.0 1.0 Miami Fort - Units 7 and 8 36.0 368 28.0 1.0 5.0 Stuart - Units 1 through 4 35.0 808 1.0 1.0 — Zimmer - Unit 1 28.1 371 12.0 1.0 5.0 Transmission (at varying percentages) 99.0 67.0 — Total 2,078 $ 147.0 $ 71.0 $ 11.0 Each of the above generating units has SCR and FGD equipment installed. On January 10, 2017, a high pressure feedwater heater shell failed on Unit 1 at the J.M. Stuart station. As a result, $6.4 million of net book value was written off, resulting in a $3.2 million loss on disposal, net of insurance recoveries. As the damage assessment process is currently ongoing, we cannot determine the impact to operations or capacity at this time. On March 17, 2017, the Board of Directors of DP&L approved the retirement of the DP&L operated and co-owned Stuart Station coal-fired and diesel-fired generating units and the Killen Station coal-fired generating unit and combustion turbine on or before June 1, 2018, and DP&L agreed with the co-owners of these facilities to proceed with this plan of retirement. On April 21, 2017, DP&L and AES Ohio Generation entered into an agreement for the sale of DP&L’s undivided interests in Zimmer and Miami Fort, for $50.0 million in cash and the assumption of certain liabilities, including environmental. The purchase price is subject to adjustment at closing based on the amount of certain inventories, pre-paid amounts, employment benefits, insurance premiums, property taxes and other costs. The sale is subject to approval by the FERC and is expected to close in the third quarter of 2017. AROs We recognize AROs in accordance with GAAP which requires legal obligations associated with the retirement of long-lived assets to be recognized at their fair value at the time those obligations are incurred. Upon initial recognition of a legal liability, costs are capitalized as part of the related long-lived asset and depreciated over the useful life of the related asset. Our legal obligations are associated with the retirement of our long-lived assets, consisting primarily of river intake and discharge structures, coal unloading facilities, loading docks, ice breakers and ash disposal facilities. Estimating the amount and timing of future expenditures of this type requires significant judgment. Management routinely updates these estimates as additional information becomes available. Changes in the Liability for Generation AROs $ in millions Balance January 1, 2017 $ 135.2 Revisions to cash flow and timing estimates (4.4 ) Accretion expense 1.4 Settlements 0.1 Balance March 31, 2017 $ 132.3 See Note 5 – Fair Value for further discussion on current year ARO additions.

Fair Value

Fair Value	3 Months Ended
	Mar. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	Fair Value The fair values of our financial instruments are based on published sources for pricing when possible. We rely on valuation models only when no other methods exist. The value of our financial instruments represents our best estimates of the fair value, which may not be the value realized in the future. The following table presents the fair value, carrying value and cost of our non-derivative instruments at March 31, 2017 and December 31, 2016 . Information about the fair value of our derivative instruments can be found in Note 6 – Derivative Instruments and Hedging Activities . March 31, 2017 December 31, 2016 $ in millions Cost Fair Value Cost Fair Value Assets Money market funds $ 0.3 $ 0.3 $ 0.4 $ 0.4 Equity securities 2.6 3.9 2.4 3.4 Debt securities 4.3 4.3 4.4 4.4 Hedge funds 0.1 0.1 — 0.1 Real estate — — 0.3 0.3 Tangible assets 0.1 0.1 0.1 0.1 Total Assets $ 7.4 $ 8.7 $ 7.6 $ 8.7 Carrying Value Fair Value Carrying Value Fair Value Liabilities Debt (a) $ 1,851.6 $ 1,940.7 $ 1,858.0 $ 1,907.7 (a) Amounts exclude immaterial capital lease obligations These financial instruments are not subject to master netting agreements or collateral requirements and as such are presented in the Condensed Consolidated Balance Sheet at their gross fair value, except for Debt, which is presented at amortized carrying value. Debt Unrealized gains or losses are not recognized in the financial statements as debt is presented at cost, net of unamortized premium or discount and deferred financing costs in the financial statements. The debt amounts include the current portion payable in the next twelve months and have maturities that range from 2019 to 2061 . Master Trust Assets DP&L established Master Trusts to hold assets that could be used for the benefit of employees participating in employee benefit plans and these assets are not used for general operating purposes. These assets are primarily comprised of open-ended mutual funds, which are valued using the net asset value per unit. These investments are recorded at fair value within Other deferred assets on the balance sheets and classified as available-for-sale. Any unrealized gains or losses are recorded in AOCI until the securities are sold. DPL had $1.2 million ( $0.8 million after tax) of unrealized gains and immaterial unrealized losses on the Master Trust assets in AOCI at March 31, 2017 and $1.0 million ( $0.6 million after tax) of unrealized gains and immaterial unrealized losses on the Master Trust assets in AOCI at December 31, 2016 . During the three months ended March 31, 2017 , $0.7 million ( $0.5 million after tax) of various investments were sold to facilitate the distribution of benefits and the unrealized gains were reversed into earnings. An immaterial amount of unrealized gains are expected to be reversed to earnings as investments are sold over the next twelve months to facilitate the distribution of benefits. Fair Value Hierarchy Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. The fair value hierarchy requires an entity to maximize the use of observable inputs and minimize the use of unobservable inputs when measuring fair value. These inputs are then categorized as: • Level 1 (quoted prices in active markets for identical assets or liabilities); • Level 2 (observable inputs such as quoted prices for similar assets or liabilities or quoted prices in markets that are not active); or • Level 3 (unobservable inputs). Valuations of assets and liabilities reflect the value of the instrument including the values associated with counterparty risk. We include our own credit risk and our counterparty’s credit risk in our calculation of fair value using global average default rates based on an annual study conducted by a large rating agency. We did not have any transfers of the fair values of our financial instruments between Level 1, Level 2 or Level 3 of the fair value hierarchy during the three months ended March 31, 2017 or 2016 . The fair value of assets and liabilities at March 31, 2017 and December 31, 2016 and the respective category within the fair value hierarchy for DPL was determined as follows: Assets and Liabilities at Fair Value Level 1 Level 2 Level 3 $ in millions Fair value at March 31, 2017 Based on Quoted Prices in Active Markets Other Observable Inputs Unobservable Inputs Assets Master Trust assets Money market funds $ 0.3 $ 0.3 $ — $ — Equity securities 3.9 — 3.9 — Debt securities 4.3 — 4.3 — Hedge funds 0.1 — 0.1 — Tangible assets 0.1 — 0.1 — Total Master Trust assets 8.7 0.3 8.4 — Derivative Assets Forward power contracts 18.9 — 18.9 — Interest rate hedges 1.4 — 1.4 — Natural gas 0.3 0.3 — — Total Derivative assets 20.6 0.3 20.3 — Total Assets $ 29.3 $ 0.6 $ 28.7 $ — Liabilities Derivative Liabilities Interest rate hedges $ 0.3 $ — $ 0.3 $ — Natural gas futures 0.5 0.5 — — Forward power contracts 18.1 — 17.0 1.1 Total Derivative liabilities 18.9 0.5 17.3 1.1 Debt 1,940.6 — 1,922.7 17.9 Total Liabilities $ 1,959.5 $ 0.5 $ 1,940.0 $ 19.0 Assets and Liabilities at Fair Value Level 1 Level 2 Level 3 $ in millions Fair value at December 31, 2016 Based on Quoted Prices in Active Markets Other Observable Inputs Unobservable Inputs Assets Master Trust assets Money market funds $ 0.4 $ 0.4 $ — $ — Equity securities 3.4 — 3.4 — Debt securities 4.4 — 4.4 — Hedge funds 0.1 — 0.1 — Real estate 0.3 — 0.3 — Tangible assets 0.1 — 0.1 — Total Master Trust assets 8.7 0.4 8.3 — Derivative assets Forward power contracts 19.5 — 19.5 — Interest rate hedges 1.2 — 1.2 — FTRs 0.1 — — 0.1 Total Derivative assets 20.8 — 20.7 0.1 Total Assets $ 29.5 $ 0.4 $ 29.0 $ 0.1 Liabilities Derivative liabilities Interest rate hedges $ 0.7 $ — $ 0.7 $ — Forward power contracts 28.5 — 26.0 2.5 Total Derivative liabilities 29.2 — 26.7 2.5 Debt 1,907.7 — 1,889.7 18.0 Total Liabilities $ 1,936.9 $ — $ 1,916.4 $ 20.5 Our financial instruments are valued using the market approach in the following categories: • Level 1 inputs are used for derivative contracts such as natural gas futures and for money market accounts that are considered cash equivalents. The fair value is determined by reference to quoted market prices and other relevant information generated by market transactions. • Level 2 inputs are used to value derivatives such as forward power contracts (which are traded on the OTC market but which are valued using prices on the NYMEX for similar contracts on the OTC market). Other Level 2 assets include open-ended mutual funds that are in the Master Trust, which are valued using observable prices based on the end of day net asset value per unit. • Level 3 inputs such as FTRs are considered a Level 3 input because the monthly auctions are considered inactive. Other Level 3 inputs include the credit valuation adjustment on some of the forward power contracts and forward power contracts in less active markets. Our Level 3 inputs are immaterial to our derivative balances as a whole and as such no further disclosures are presented. Approximately 93.6% of the inputs to the fair value of our derivative instruments are from quoted market prices. Our debt is fair valued for disclosure purposes only and most of the fair values are determined using quoted market prices in inactive markets. These fair value inputs are considered Level 2 in the fair value hierarchy. As the Wright-Patterson Air Force Base loan is not publicly traded, fair value is assumed to equal carrying value. These fair value inputs are considered Level 3 in the fair value hierarchy as there are no observable inputs. Additional Level 3 disclosures are not presented since debt is not recorded at fair value. Non-recurring Fair Value Measurements We use the cost approach to determine the fair value of our AROs, which is estimated by discounting expected cash outflows to their present value at the initial recording of the liability. Cash outflows are based on the approximate future disposal cost as determined by market information, historical information or other management estimates. These inputs to the fair value of the AROs would be considered Level 3 inputs under the fair value hierarchy. As a result of changes in our estimates of costs to be incurred for our AROs, we decreased our AROs by $4.4 million in the first quarter of 2017. AROs for ash ponds, asbestos, river structures and underground storage tanks decreased by a net amount of $(3.1) million and decreased by a net amount of $(0.6) million during the three months ended March 31, 2017 and 2016 , respectively. On March 17, 2017, the Board of Directors of DP&L approved the retirement of the DP&L operated and co-owned Stuart Station coal-fired and diesel-fired generating units and the Killen Station coal-fired generating unit and combustion turbine (collectively, the “Facilities”) on or before June 1, 2018, and DP&L agreed with the co-owners of the Facilities to proceed with this plan of retirement. As such, w e performed a long-lived asset impairment analysis and determined that the carrying amounts of the Facilities were not recoverable. See Note 14 – Fixed-asset Impairment . When evaluating impairment of long-lived assets, we measure fair value using the applicable fair value measurement guidance. Impairment expense is measured by comparing the fair value at the evaluation date to the carrying amount. The following table summarizes Long-lived assets measured at fair value on a non-recurring basis during the period and their level within the fair value hierarchy (there were no impairments during the three months ended March 31, 2016): $ in millions Three months ended March 31, 2017 Carrying Fair Value Gross Amount (b) Level 1 Level 2 Level 3 Loss Assets Long-lived assets (a) Stuart $ 42.4 $ — $ — $ 3.3 $ 39.1 Killen $ 35.2 $ — $ — $ 7.9 $ 27.3 (a) See Note 14 – Fixed-asset Impairment for further information (b) Carrying amount at date of valuation The following summarizes the significant unobservable inputs used in the Level 3 measurement on a non-recurring basis during the three months ended March 31, 2017: $ in millions Fair value Valuation technique Unobservable input Weighted average Long-lived assets held and used: Stuart $ 3.3 Discounted cash flow Pre-tax operating margin 10% Weighted-average cost of capital 7% Killen $ 7.9 Discounted cash flow Pre-tax operating margin 22% Weighted-average cost of capital 7%
THE DAYTON POWER AND LIGHT COMPANY [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	Fair Value The fair values of our financial instruments are based on published sources for pricing when possible. We rely on valuation models only when no other methods exist. The value of our financial instruments represents our best estimates of the fair value, which may not be the value realized in the future. The following table presents the fair value, carrying value and cost of our non-derivative instruments at March 31, 2017 and December 31, 2016 . Information about the fair value of our derivative instruments can be found in Note 6 – Derivative Instruments and Hedging Activities . March 31, 2017 December 31, 2016 $ in millions Cost Fair Value Cost Fair Value Assets Money market funds $ 0.3 $ 0.3 $ 0.4 $ 0.4 Equity securities 2.6 3.9 2.4 3.4 Debt securities 4.3 4.3 4.4 4.4 Hedge funds 0.1 0.1 — 0.1 Real estate — — 0.3 0.3 Tangible assets 0.1 0.1 0.1 0.1 Total assets $ 7.4 $ 8.7 $ 7.6 $ 8.7 Carrying Value Fair Value Carrying Value Fair Value Liabilities Debt (a) $ 748.3 $ 762.3 $ 749.0 $ 763.5 (a) Amounts exclude immaterial capital lease obligations These financial instruments are not subject to master netting agreements or collateral requirements and as such are presented in the Condensed Balance Sheet at their gross fair value, except for Debt, which is presented at amortized carrying value. Debt Unrealized gains or losses are not recognized in the financial statements as debt is presented at cost, net of unamortized premium or discount and deferred financing costs in the financial statements. The debt amounts include the current portion payable in the next twelve months and have maturities that range from 2020 to 2061 . Master Trust Assets DP&L established Master Trusts to hold assets that could be used for the benefit of employees participating in employee benefit plans and these assets are not used for general operating purposes. These assets are primarily comprised of open-ended mutual funds, which are valued using the net asset value per unit. These investments are recorded at fair value within Other deferred assets on the balance sheets and classified as available-for-sale. Any unrealized gains or losses are recorded in AOCI until the securities are sold. DP&L had $1.3 million ( $0.9 million after tax) of unrealized gains and immaterial unrealized losses on the Master Trust assets in AOCI at March 31, 2017 and $1.1 million ( $0.7 million after tax) in unrealized gains and immaterial unrealized losses on the Master Trust assets in AOCI at December 31, 2016 . During the three months ended March 31, 2017 , $0.7 million ( $0.5 million after tax) of various investments were sold to facilitate the distribution of benefits and the unrealized gains were reversed into earnings. An immaterial amount of unrealized gains are expected to be reversed to earnings as investments are sold over the next twelve months to facilitate the distribution of benefits. Fair Value Hierarchy Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. The fair value hierarchy requires an entity to maximize the use of observable inputs and minimize the use of unobservable inputs when measuring fair value. These inputs are then categorized as: • Level 1 (quoted prices in active markets for identical assets or liabilities); • Level 2 (observable inputs such as quoted prices for similar assets or liabilities or quoted prices in markets that are not active); or • Level 3 (unobservable inputs). Valuations of assets and liabilities reflect the value of the instrument including the values associated with counterparty risk. We include our own credit risk and our counterparty’s credit risk in our calculation of fair value using global average default rates based on an annual study conducted by a large rating agency. We did not have any transfers of the fair values of our financial instruments between Level 1, Level 2 or Level 3 of the fair value hierarchy during the three months ended March 31, 2017 or 2016 . The fair value of assets and liabilities at March 31, 2017 and December 31, 2016 and the respective category within the fair value hierarchy for DP&L was determined as follows: Assets and Liabilities at Fair Value Level 1 Level 2 Level 3 $ in millions Fair value at March 31, 2017 Based on Quoted Prices in Active Markets Other Observable Inputs Unobservable Inputs Assets Master Trust assets Money market funds $ 0.3 $ 0.3 $ — $ — Equity securities 3.9 — 3.9 — Debt securities 4.3 — 4.3 — Hedge funds 0.1 — 0.1 — Tangible assets 0.1 — 0.1 — Total Master Trust assets 8.7 0.3 8.4 — Derivative assets Natural gas futures 0.3 0.3 — — Interest rate hedges 1.4 — 1.4 — Forward power contracts 19.0 — 19.0 — Total derivative assets 20.7 0.3 20.4 — Total assets $ 29.4 $ 0.6 $ 28.8 $ — Liabilities Derivative liabilities Interest rate hedges $ 0.3 $ — $ 0.3 $ — Natural gas futures 0.5 0.5 — — Forward power contracts 18.1 — 17.0 1.1 Total derivative liabilities 18.9 0.5 17.3 1.1 Debt 762.3 — 744.4 17.9 Total liabilities $ 781.2 $ 0.5 $ 761.7 $ 19.0 Assets and Liabilities at Fair Value Level 1 Level 2 Level 3 $ in millions Fair value at December 31, 2016 Based on Quoted Prices in Active Markets Other Observable Inputs Unobservable Inputs Assets Master Trust assets Money market funds $ 0.4 $ 0.4 $ — $ — Equity securities 3.4 — 3.4 — Debt securities 4.4 — 4.4 — Hedge funds 0.1 — 0.1 — Real estate 0.3 — 0.3 — Tangible assets 0.1 0.1 — Total Master Trust assets 8.7 0.4 8.3 — Derivative assets FTRs 0.1 — — 0.1 Interest rate hedges 1.2 — 1.2 — Forward power contracts 19.5 — 19.5 — Total Derivative assets 20.8 — 20.7 0.1 Total assets $ 29.5 $ 0.4 $ 29.0 $ 0.1 Liabilities Derivative liabilities Interest rate hedges $ 0.7 $ — $ 0.7 $ — Forward power contracts 28.5 — 26.0 2.5 Total Derivative liabilities 29.2 — 26.7 2.5 Debt 763.5 — 745.5 18.0 Total liabilities $ 792.7 $ — $ 772.2 $ 20.5 Our financial instruments are valued using the market approach in the following categories: • Level 1 inputs are used for derivative contracts such as natural gas futures and for money market accounts that are considered cash equivalents. The fair value is determined by reference to quoted market prices and other relevant information generated by market transactions. • Level 2 inputs are used to value derivatives such as forward power contracts (which are traded on the OTC market but which are valued using prices on the NYMEX for similar contracts on the OTC market). Other Level 2 assets include open-ended mutual funds that are in the Master Trust, which are valued using observable prices based on the end of day net asset value per unit. • Level 3 inputs such as FTRs are considered a Level 3 input because the monthly auctions are considered inactive. Other Level 3 inputs include the credit valuation adjustment on some of the forward power contracts and forward power contracts in less active markets. Our Level 3 inputs are immaterial to our derivative balances as a whole and as such no further disclosures are presented. Our debt is fair valued for disclosure purposes only and most of the fair values are determined using quoted market prices in inactive markets. These fair value inputs are considered Level 2 in the fair value hierarchy. As the Wright-Patterson Air Force Base loan is not publicly traded, fair value is assumed to equal carrying value. These fair value inputs are considered Level 3 in the fair value hierarchy as there are no observable inputs. Additional Level 3 disclosures are not presented since debt is not recorded at fair value. Approximately 93.6% of the inputs to the fair value of our derivative instruments are from quoted market prices. Non-recurring Fair Value Measurements We use the cost approach to determine the fair value of our AROs, which is estimated by discounting expected cash outflows to their present value at the initial recording of the liability. Cash outflows are based on the approximate future disposal cost as determined by market information, historical information or other management estimates. These inputs to the fair value of the AROs would be considered Level 3 inputs under the fair value hierarchy. As a result of changes in our estimates of costs to be incurred for our AROs, we decreased our AROs by $4.4 million in the first quarter of 2017. AROs for ash ponds, asbestos, river structures and underground storage tanks decreased by a net amount of $(2.9) million and decreased by a net amount of $(0.6) million during the three months ended March 31, 2017 and 2016 , respectively. On March 17, 2017, the Board of Directors of DP&L approved the retirement of the DP&L operated and co-owned Stuart Station coal-fired and diesel-fired generating units and the Killen Station coal-fired generating unit and combustion turbine (collectively, the “Facilities”) on or before June 1, 2018, and DP&L agreed with the co-owners of the Facilities to proceed with this plan of retirement. As such, w e performed a long-lived asset impairment analysis and determined that the carrying amounts of the Facilities were not recoverable. See Note 14 – Fixed-asset Impairment . When evaluating impairment of long-lived assets, we measure fair value using the applicable fair value measurement guidance. Impairment expense is measured by comparing the fair value at the evaluation date to the carrying amount. The following table summarizes Long-lived assets measured at fair value on a non-recurring basis during the period and their level within the fair value hierarchy (there were no impairments during the three months ended March 31, 2016): $ in millions Three months ended March 31, 2017 Carrying Fair Value Gross Amount (b) Level 1 Level 2 Level 3 Loss Assets Long-lived assets (a) Stuart $ 42.3 $ — $ — $ 3.3 $ 39.0 Killen $ 35.2 $ — $ — $ 7.9 $ 27.3 (a) See Note 14 – Fixed-asset Impairment for further information (b) Carrying amount at date of valuation The following summarizes the significant unobservable inputs used in the Level 3 measurement on a non-recurring basis during the three months ended March 31, 2017: $ in millions Fair value Valuation technique Unobservable input Weighted average Long-lived assets held and used: Stuart $ 3.3 Discounted cash flow Pre-tax operating margin 10 % Weighted-average cost of capital 7% Killen $ 7.9 Discounted cash flow Pre-tax operating margin 22 % Weighted-average cost of capital 7%

Derivative Instruments and Hedg

Derivative Instruments and Hedging Activities	3 Months Ended
	Mar. 31, 2017
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative Instruments and Hedging Activities	Derivative Instruments and Hedging Activities In the normal course of business, DPL enters into various financial arrangements, including derivative financial instruments. We use derivatives principally to manage the risk of changes in market prices for commodities. The derivatives that we use to economically hedge these risks are governed by our risk management policies for forward and futures contracts. Our net positions are continually assessed within our structured hedging programs to determine whether new or offsetting transactions are required. The objective of the hedging program is to mitigate financial risks while ensuring that we have adequate resources to meet our requirements. We monitor and value derivative positions monthly as part of our risk management processes. We use published sources for pricing, when possible, to mark positions to market. All of our derivative instruments are used for risk management purposes and are designated as normal purchase/normal sale, cash flow hedges or marked to market each reporting period. At March 31, 2017 , DPL had the following outstanding derivative instruments: Commodity Accounting Treatment (a) Unit Purchases (in thousands) Sales (in thousands) Net Purchases/ (Sales) (in thousands) FTRs Not designated MWh 0.9 — 0.9 Natural gas futures Not designated Dths 17,127.5 — 17,127.5 Forward power contracts Designated MWh 1,276.6 (6,250.9 ) (4,974.3 ) Forward power contracts Not designated MWh 1,727.3 (2,052.6 ) (325.3 ) Interest rate swaps Designated USD $ 200,000.0 $ — $ 200,000.0 (a) Refers to whether the derivative instruments have been designated as a cash flow hedge. At December 31, 2016 , DPL had the following outstanding derivative instruments: Commodity Accounting Treatment (a) Unit Purchases (in thousands) Sales (in thousands) Net Purchases/ (Sales) (in thousands) FTRs Not designated MWh 2.3 — 2.3 Natural gas futures Not designated Dths 1,590.0 — 1,590.0 Forward power contracts Designated MWh 342.9 (9,974.5 ) (9,631.6 ) Forward power contracts Not designated MWh 2,568.3 (2,020.9 ) 547.4 Interest rate swaps Designated USD $ 200,000.0 $ — $ 200,000.0 (a) Refers to whether the derivative instruments have been designated as a cash flow hedge. Cash Flow Hedges As part of our risk management processes, we identify the relationships between hedging instruments and hedged items, as well as the risk management objective and strategy for undertaking various hedge transactions. The fair value of cash flow hedges is determined by observable market prices available as of the balance sheet dates and will continue to fluctuate with changes in market prices up to contract expiration. The effective portion of the hedging transaction is recognized in AOCI and transferred to earnings using specific identification of each contract when the forecasted hedged transaction takes place or when the forecasted hedged transaction is probable of not occurring. The ineffective portion of the cash flow hedge is recognized in earnings in the current period. All risk components were taken into account to determine the hedge effectiveness of the cash flow hedges. We enter into forward power contracts to manage commodity price risk exposure related to our generation of electricity. We do not hedge all commodity price risk. We reclassify gains and losses on forward power contracts from AOCI into earnings in those periods in which the contracts settle. In November 2016, we entered into two interest rate swaps to hedge the variable interest on our $200.0 million variable interest rate tax-exempt First Mortgage Bonds. The interest rate swaps have a combined notional amount of $200.0 million and will settle monthly based on a one month LIBOR. We use the income approach to value the swaps, which consists of forecasting future cash flows based on contractual notional amounts and applicable and available market data as of the valuation date. The most common market data inputs used in the income approach include volatilities, spot and forward benchmark interest rates (LIBOR). Forward rates with the same tenor as the derivative instrument being valued are generally obtained from published sources, with these forward rates being assessed quarterly at a portfolio-level for reasonableness versus comparable published rates. We reclassify gains and losses on the swaps out of AOCI and into earnings in those periods in which hedged interest payments occur. We had previously entered into interest rate derivative contracts to manage interest rate exposure related to anticipated borrowings of fixed-rate debt. These interest rate derivative contracts were settled in the third quarter of 2013 and we continue to amortize amounts out of AOCI into interest expense. The following table provides information for DPL concerning gains or losses recognized in AOCI for the cash flow hedges for the three months ended March 31, 2017 and 2016 : Three months ended Three months ended March 31, 2017 March 31, 2016 Interest Interest $ in millions (net of tax) Power Rate Hedge Power Rate Hedge Beginning accumulated derivative gains / (losses) in AOCI $ (4.3 ) $ 17.4 $ 9.2 $ 17.5 Net gains associated with current period hedging transactions 4.9 0.3 21.5 — Net gains / (losses) reclassified to earnings Interest expense — (0.2 ) — — Revenues (0.9 ) — (11.0 ) — Purchased power 2.1 — 2.8 — Ending accumulated derivative gains in AOCI $ 1.8 $ 17.5 $ 22.5 $ 17.5 Portion expected to be reclassified to earnings in the next twelve months (a) $ 2.0 $ (0.2 ) Maximum length of time that we are hedging our exposure to variability in future cash flows related to forecasted transactions (in months) 17 41 (a) The actual amounts that we reclassify from AOCI to earnings related to power can differ from the estimate above due to market price changes. Derivatives not designated as hedges Certain derivative contracts are entered into on a regular basis as part of our risk management program but do not qualify for hedge accounting or the normal purchase and sales scope exceptions under FASC 815. Accordingly, such contracts are recorded at fair value with changes in the fair value charged or credited to the Condensed Consolidated Statements of Operations in the period in which the change occurred. This is commonly referred to as “MTM accounting.” Contracts we enter into as part of our risk management program may be settled financially, by physical delivery, or net settled with the counterparty. FTRs, natural gas futures, and certain forward power contracts are currently marked to market. Certain qualifying derivative instruments have been designated as normal purchases or normal sales contracts, as provided under GAAP. Derivative contracts that have been designated as normal purchases or normal sales under GAAP are not subject to MTM accounting and are recognized in the Condensed Consolidated Statements of Operations on an accrual basis. Financial Statement Effect The following tables present the amount and classification within the Condensed Consolidated Statements of Operations of the gains and losses on DPL’s derivatives not designated as hedging instruments for the three months ended March 31, 2017 and 2016 : For the three months ended March 31, 2017 $ in millions FTRs Power Natural Gas Total Change in unrealized loss $ — $ (0.1 ) $ (0.1 ) $ (0.2 ) Realized gain / (loss) 0.2 (2.6 ) (0.2 ) (2.6 ) Total $ 0.2 $ (2.7 ) $ (0.3 ) $ (2.8 ) Recorded in Income Statement: gain / (loss) Revenues $ — $ (6.7 ) $ — $ (6.7 ) Purchased power 0.2 4.0 (0.3 ) 3.9 Total $ 0.2 $ (2.7 ) $ (0.3 ) $ (2.8 ) For the three months ended March 31, 2016 $ in millions FTRs Power Natural Gas Total Change in unrealized gain / (loss) $ 0.1 $ (1.5 ) $ (0.2 ) $ (1.6 ) Realized gain / (loss) 0.2 (0.4 ) (0.2 ) (0.4 ) Total $ 0.3 $ (1.9 ) $ (0.4 ) $ (2.0 ) Recorded in Income Statement: gain / (loss) Revenue $ — $ (1.1 ) $ — $ (1.1 ) Purchased power 0.3 (0.8 ) (0.4 ) (0.9 ) Total $ 0.3 $ (1.9 ) $ (0.4 ) $ (2.0 ) DPL has elected not to offset derivative assets and liabilities and not to offset net derivative positions against the right to reclaim cash collateral pledged (an asset) or the obligation to return cash collateral received (a liability) under derivative agreements. The following tables summarize the derivative positions presented in the balance sheet where a right of offset exists under these arrangements and related cash collateral received or pledged. The following table presents the fair value and balance sheet classification of DPL’s derivative instruments at March 31, 2017 : Fair Values of Derivative Instruments at March 31, 2017 Gross Amounts Not Offset in the Condensed Consolidated Balance Sheets $ in millions Hedging Designation Gross Fair Value as presented in the Condensed Consolidated Balance Sheets Financial Instruments with Same Counterparty in Offsetting Position Cash Collateral Net Balance Fair Value Assets Short-term derivative positions (presented in Other prepayments and current assets) Forward power contracts Designated $ 12.7 $ (8.6 ) $ — $ 4.1 Forward power contracts Not designated 6.1 (5.5 ) — 0.6 Natural gas futures Not designated 0.3 (0.2 ) — 0.1 Long-term derivative positions (presented in Other deferred assets) Interest rate swap Designated 1.4 — — 1.4 Forward power contracts Not designated 0.1 (0.1 ) — — Total assets $ 20.6 $ (14.4 ) $ — $ 6.2 Liabilities Short-term derivative positions (presented in Other current liabilities) Forward power contracts Designated $ 9.7 $ (8.6 ) $ — $ 1.1 Interest rate swap Designated 0.3 — — 0.3 Forward power contracts Not designated 8.1 (5.5 ) (0.1 ) 2.5 Natural gas futures Not designated 0.2 (0.2 ) — — Long-term derivative positions (presented in Other deferred credits) Forward power contracts Designated 0.1 — (0.1 ) — Natural gas futures Not designated 0.3 — (0.3 ) — Forward power contracts Not designated 0.2 (0.1 ) — 0.1 Total liabilities $ 18.9 $ (14.4 ) $ (0.5 ) $ 4.0 The following table presents the fair value and balance sheet classification of DPL’s derivative instruments at December 31, 2016 : Fair Values of Derivative Instruments at December 31, 2016 Gross Amounts Not Offset in the Condensed Consolidated Balance Sheets $ in millions Hedging Designation Gross Fair Value as presented in the Condensed Consolidated Balance Sheets Financial Instruments with Same Counterparty in Offsetting Position Cash Collateral Net Balance Fair Value Assets Short-term derivative positions (presented in Other prepayments and current assets) Forward power contracts Designated $ 11.0 $ (10.5 ) $ — $ 0.5 Forward power contracts Not designated 6.0 (4.7 ) — 1.3 FTRs Not designated 0.1 — — 0.1 Long-term derivative positions (presented in Other deferred assets) Interest rate swaps Designated 1.2 — — 1.2 Forward power contracts Designated 0.6 (0.6 ) — — Forward power contracts Not designated 1.9 (1.0 ) — 0.9 Total assets $ 20.8 $ (16.8 ) $ — $ 4.0 Liabilities Short-term derivative positions (presented in Other current liabilities) Interest rate swaps Designated $ 0.7 $ — $ — $ 0.7 Forward power contracts Designated 16.4 (10.5 ) (5.5 ) 0.4 Forward power contracts Not designated 7.7 (4.7 ) — 3.0 Long-term derivative positions (presented in Other deferred credits) Forward power contracts Designated 2.4 (0.6 ) (0.8 ) 1.0 Forward power contracts Not designated 2.0 (1.0 ) — 1.0 Total liabilities $ 29.2 $ (16.8 ) $ (6.3 ) $ 6.1 Credit risk-related contingent features Certain of our OTC commodity derivative contracts are under master netting agreements that contain provisions that require us to post collateral if our credit ratings drop below certain thresholds. We have crossed that threshold with one counterparty to the derivative instruments and they could request that we post collateral of $0.9 million at this time. The aggregate fair value of DPL’s commodity derivative instruments that were in a MTM loss position at March 31, 2017 was $18.9 million . $0.5 million of collateral was posted directly with third parties and in a broker margin account which offsets our loss positions on the forward contracts. This liability position is further offset by the asset position of counterparties with master netting agreements of $14.4 million . Since our debt is below investment grade, we could have to post collateral for the remaining $4.0 million .
THE DAYTON POWER AND LIGHT COMPANY [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative Instruments and Hedging Activities	Derivative Instruments and Hedging Activities In the normal course of business, DP&L enters into various financial arrangements, including derivative financial instruments. We use derivatives principally to manage the risk of changes in market prices for commodities. The derivatives that we use to economically hedge these risks are governed by our risk management policies for forward and futures contracts. Our net positions are continually assessed within our structured hedging programs to determine whether new or offsetting transactions are required. The objective of the hedging program is to mitigate financial risks while ensuring that we have adequate resources to meet our requirements. We monitor and value derivative positions monthly as part of our risk management processes. We use published sources for pricing, when possible, to mark positions to market. All of our derivative instruments are used for risk management purposes and are designated as normal purchase/normal sale, cash flow hedges or marked to market each reporting period. At March 31, 2017 , DP&L had the following outstanding derivative instruments: Commodity Accounting Treatment (a) Unit Purchases (in thousands) Sales (in thousands) Net Purchases/ (Sales) (in thousands) FTRs Not designated MWh 0.9 — 0.9 Natural gas futures Not designated Dths 17,127.5 — 17,127.5 Forward power contracts Designated MWh 1,276.6 (6,250.9 ) (4,974.3 ) Forward power contracts Not designated MWh 1,727.3 (2,057.9 ) (330.6 ) Interest rate swaps Designated USD $ 200,000.0 $ — $ 200,000.0 (a) Refers to whether the derivative instruments have been designated as a cash flow hedge. At December 31, 2016 , DP&L had the following outstanding derivative instruments: Commodity Accounting Treatment (a) Unit Purchases (in thousands) Sales (in thousands) Net Purchases/ (Sales) (in thousands) FTRs Not designated MWh 2.3 — 2.3 Natural gas futures Not designated Dths 1,590.0 — 1,590.0 Forward power contracts Designated MWh 342.9 (9,974.5 ) (9,631.6 ) Forward power contracts Not designated MWh 2,568.3 (2,037.5 ) 530.8 Interest rate swaps Designated USD $ 200,000.0 $ — $ 200,000.0 (a) Refers to whether the derivative instruments have been designated as a cash flow hedge. Cash Flow Hedges As part of our risk management processes, we identify the relationships between hedging instruments and hedged items, as well as the risk management objective and strategy for undertaking various hedge transactions. The fair value of cash flow hedges is determined by observable market prices available as of the balance sheet dates and will continue to fluctuate with changes in market prices up to contract expiration. The effective portion of the hedging transaction is recognized in AOCI and transferred to earnings using specific identification of each contract when the forecasted hedged transaction takes place or when the forecasted hedged transaction is probable of not occurring. The ineffective portion of the cash flow hedge is recognized in earnings in the current period. All risk components were taken into account to determine the hedge effectiveness of the cash flow hedges. We enter into forward power contracts to manage commodity price risk exposure related to our generation of electricity. We do not hedge all commodity price risk. We reclassify gains and losses on forward power contracts from AOCI into earnings in those periods in which the contracts settle. In November 2016, we entered into two interest rate swaps to hedge the variable interest on our $200.0 million variable interest rate tax-exempt First Mortgage Bonds. The interest rate swaps have a combined notional amount of $200.0 million and will settle monthly based on a one month LIBOR. We use the income approach to value the swaps, which consists of forecasting future cash flows based on contractual notional amounts and applicable and available market data as of the valuation date. The most common market data inputs used in the income approach include volatilities, spot and forward benchmark interest rates (LIBOR). Forward rates with the same tenor as the derivative instrument being valued are generally obtained from published sources, with these forward rates being assessed quarterly at a portfolio-level for reasonableness versus comparable published rates. We reclassify gains and losses on the swaps out of AOCI and into earnings in those periods in which hedged interest payments occur. The following table provides information for DP&L concerning gains or losses recognized in AOCI for the cash flow hedges for the three months ended March 31, 2017 and 2016 : Three months ended Three months ended March 31, 2017 March 31, 2016 Interest Interest $ in millions (net of tax) Power Rate Hedge Power Rate Hedge Beginning accumulated derivative gains / (losses) in AOCI $ (4.3 ) $ 1.6 $ 9.2 $ 2.0 Net gains associated with current period hedging transactions 4.9 0.3 21.5 — Net gains / (losses) reclassified to earnings Interest expense — (0.2 ) — (0.2 ) Revenues (0.9 ) — (11.0 ) — Purchased power 2.1 — 2.8 — Ending accumulated derivative gains in AOCI $ 1.8 $ 1.7 $ 22.5 $ 1.8 Portion expected to be reclassified to earnings in the next twelve months (a) $ 2.0 $ (0.2 ) Maximum length of time that we are hedging our exposure to variability in future cash flows related to forecasted transactions (in months) 17 41 (a) The actual amounts that we reclassify from AOCI to earnings related to power can differ from the estimate above due to market price changes. Derivatives not designated as hedges Certain derivative contracts are entered into on a regular basis as part of our risk management program but do not qualify for hedge accounting or the normal purchase and sales scope exceptions under FASC 815. Accordingly, such contracts are recorded at fair value with changes in the fair value charged or credited to the Condensed Statements of Operations in the period in which the change occurred. This is commonly referred to as “MTM accounting.” Contracts we enter into as part of our risk management program may be settled financially, by physical delivery, or net settled with the counterparty. FTRs, natural gas futures, and certain forward power contracts are currently marked to market. Certain qualifying derivative instruments have been designated as normal purchases or normal sales contracts, as provided under GAAP. Derivative contracts that have been designated as normal purchases or normal sales under GAAP are not subject to MTM accounting and are recognized in the Condensed Statements of Operations on an accrual basis. Financial Statement Effect The following tables present the amount and classification within the Condensed Statements of Operations of the gains and losses on DP&L's derivatives not designated as hedging instruments for the three months ended March 31, 2017 and 2016 : For the three months ended March 31, 2017 $ in millions FTRs Power Natural Gas Total Change in unrealized loss $ — $ (0.1 ) $ (0.1 ) $ (0.2 ) Realized gain / (loss) 0.2 (2.6 ) (0.2 ) (2.6 ) Total $ 0.2 $ (2.7 ) $ (0.3 ) $ (2.8 ) Recorded in Income Statement: gain / (loss) Revenues $ — $ (6.7 ) $ — $ (6.7 ) Purchased power 0.2 4.0 (0.3 ) 3.9 Total $ 0.2 $ (2.7 ) $ (0.3 ) $ (2.8 ) For the three months ended March 31, 2016 $ in millions FTRs Power Natural Gas Total Change in unrealized gain / (loss) $ 0.1 $ (1.9 ) (0.2 ) $ (2.0 ) Realized gain / (loss) 0.2 (0.3 ) (0.2 ) (0.3 ) Total $ 0.3 $ (2.2 ) $ (0.4 ) $ (2.3 ) Recorded in Income Statement: gain / (loss) Revenues — (1.4 ) — (1.4 ) Purchased power 0.3 (0.8 ) (0.4 ) (0.9 ) Total $ 0.3 $ (2.2 ) $ (0.4 ) $ (2.3 ) DP&L has elected not to offset derivative assets and liabilities and not to offset net derivative positions against the right to reclaim cash collateral pledged (an asset) or the obligation to return cash collateral received (a liability) under derivative agreements. The following tables summarize the derivative positions presented in the balance sheet where a right of offset exists under these arrangements and related cash collateral received or pledged. The following table presents the fair value and balance sheet classification of DP&L’s derivative instruments at March 31, 2017 : Fair Values of Derivative Instruments at March 31, 2017 Gross Amounts Not Offset in the Condensed Balance Sheets $ in millions Hedging Designation Gross Fair Value as presented in the Condensed Balance Sheets Financial Instruments with Same Counterparty in Offsetting Position Cash Collateral Net Balance Fair Value Assets Short-term derivative positions (presented in Other prepayments and current assets) Forward power contracts Designated $ 12.7 $ (8.6 ) $ — $ 4.1 Forward power contracts Not designated 6.2 (5.5 ) — 0.7 Natural gas futures Not designated 0.3 (0.2 ) — 0.1 Long-term derivative positions (presented in Other deferred assets) Interest rate swaps Designated 1.4 — — 1.4 Forward power contracts Not designated 0.1 (0.1 ) — — Total assets $ 20.7 $ (14.4 ) $ — $ 6.3 Liabilities Short-term derivative positions (presented in Other current liabilities) Forward power contracts Designated $ 9.7 $ (8.6 ) $ — $ 1.1 Interest rate swaps Designated 0.3 — — 0.3 Forward power contracts Not designated 8.1 (5.5 ) (0.1 ) 2.5 Natural gas futures Not designated 0.2 (0.2 ) — — Long-term derivative positions (presented in Other deferred credits) Forward power contracts Designated 0.1 — (0.1 ) — Natural gas futures Not designated 0.3 — (0.3 ) — Forward power contracts Not designated 0.2 (0.1 ) — 0.1 Total liabilities $ 18.9 $ (14.4 ) $ (0.5 ) $ 4.0 The following table presents the fair value and balance sheet classification of DP&L’s derivative instruments at December 31, 2016 : Fair Values of Derivative Instruments at December 31, 2016 Gross Amounts Not Offset in the Condensed Balance Sheets $ in millions Hedging Designation Gross Fair Value as presented in the Condensed Balance Sheets Financial Instruments with Same Counterparty in Offsetting Position Cash Collateral Net Balance Fair Value Assets Short-term derivative positions (presented in Other prepayments and current assets) Forward power contracts Designated $ 11.0 $ (10.5 ) $ — $ 0.5 Forward power contracts Not designated 6.0 (4.7 ) — 1.3 FTRs Not designated 0.1 — — 0.1 Long-term derivative positions (presented in Other deferred assets) Interest rate swaps Designated 1.2 — — 1.2 Forward power contracts Designated 0.6 (0.6 ) — — Forward power contracts Not designated 1.9 (1.0 ) — 0.9 Total assets $ 20.8 $ (16.8 ) $ — $ 4.0 Liabilities Short-term derivative positions (presented in Other current liabilities) Forward power contracts Designated $ 16.4 $ (10.5 ) $ (5.5 ) $ 0.4 Interest rate swaps Designated 0.7 — — 0.7 Forward power contracts Not designated 7.7 (4.7 ) — 3.0 Long-term derivative positions (presented in Other deferred credits) Forward power contracts Designated 2.4 (0.6 ) (0.8 ) 1.0 Forward power contracts Not designated 2.0 (1.0 ) — 1.0 Total liabilities $ 29.2 $ (16.8 ) $ (6.3 ) $ 6.1 Credit risk-related contingent features Certain of our OTC commodity derivative contracts are under master netting agreements that contain provisions that require us to post collateral if our credit ratings drop below certain thresholds. We have crossed that threshold with one counterparty to the derivative instruments and they could request that we post collateral of $0.9 million at this time. The aggregate fair value of DP&L’s commodity derivative instruments that were in a MTM loss position at March 31, 2017 was $18.9 million . $0.5 million of collateral was posted directly with third parties and in a broker margin account which offsets our loss positions on the forward contracts. This liability position is further offset by the asset position of counterparties with master netting agreements of $14.4 million . Since our debt is below investment grade, we could have to post collateral for the remaining $4.0 million .

Debt Obligations

Debt Obligations	3 Months Ended
	Mar. 31, 2017
Debt Instrument [Line Items]
Debt Obligations	Debt The following table provides a summary of DPL's outstanding debt. Interest March 31, December 31, $ in millions Rate Maturity 2017 2016 Term loan - rates from 4.01% - 4.04% (a) and 4.00% - 4.01% (b) 2022 $ 443.9 $ 445.0 Tax-exempt First Mortgage Bonds 4.8% 2036 100.0 100.0 Tax-exempt First Mortgage Bonds - rates from 1.52% - 1.53% (a) and 1.29% - 1.42% (b) 2020 200.0 200.0 U.S. Government note 4.2% 2061 17.9 18.0 Capital leases 0.4 0.4 Unamortized deferred financing costs (10.1 ) (10.7 ) Unamortized debt discount and premiums, net (5.3 ) (5.5 ) Total long-term debt at consolidated subsidiary 746.8 747.2 Bank term loan - rates from 3.02% - 3.73% (a) and 2.67% - 3.02% (b) 2020 118.8 125.0 Senior unsecured notes 6.75% 2019 200.0 200.0 Senior unsecured notes 7.25% 2021 780.0 780.0 Note to DPL Capital Trust II (c) 8.125% 2031 15.6 15.6 Unamortized deferred financing costs (8.4 ) (8.8 ) Unamortized debt discounts and premiums, net (0.8 ) (0.6 ) Total long-term debt 1,852.0 1,858.4 Less: current portion (29.7 ) (29.7 ) Long-term debt, net of current portion $ 1,822.3 $ 1,828.7 (a) Range of interest rates for the three months ended March 31, 2017 . (b) Range of interest rates for the year ended December 31, 2016 . (c) Note payable to related party. See Note 11 – Related Party Transactions for additional information. Premiums or discounts are amortized over the remaining life of the debt using the effective interest method. Debt covenants and restrictions DP&L’s unsecured revolving credit agreement and Bond Purchase and Covenants Agreement have two financial covenants. The first measures Total Debt to Total Capitalization and is calculated at the end of each fiscal quarter by dividing total debt at the end of the quarter by total capitalization at the end of the quarter. The second financial covenant ratio compares EBITDA to Interest Expense and is calculated at the end of each fiscal quarter by dividing EBITDA for the four prior fiscal quarters by the consolidated interest charges for the same period. On February 21, 2017, DP&L and its lenders amended DP&L’s revolving credit agreement and Bond Purchase and Covenant Agreement. These amendments modified the definition of Consolidated Net Worth (which is used for measuring the Total Debt to Total Capitalization ratio under each of the agreements), to exclude, through March 31, 2018, non-cash charges related directly to impairments of coal generation assets in DP&L's fiscal quarter ending December 31, 2016 and thereafter. With this amendment, DP&L’s Total Debt to Total Capitalization ratio for the period ending March 31, 2017 is 0.53 to 1.00. The amendment also changed, for each amendment, the dates after generation separation during which compliance with the Total Capitalization ratio detailed above shall be suspended if long-term indebtedness, as determined by the PUCO, is less than or equal to $750.0 million . As noted above this time period previously was January 1, 2017 to December 31, 2017, and is now the twelve months immediately subsequent to the separation of the generation assets from DP&L . The cost of borrowing under DP&L's unsecured revolving credit agreement and Bond Purchase and Covenants Agreement adjust under certain credit rating scenarios. DPL’s revolving credit agreement and term loan have two financial covenants. The first financial covenant, a Total Debt to EBITDA ratio, is calculated at the end of each fiscal quarter by dividing total debt at the end of the current quarter by consolidated EBITDA for the four prior fiscal quarters. The second financial covenant, an EBITDA to Interest Expense ratio, is calculated, at the end of each fiscal quarter, by dividing EBITDA for the four prior fiscal quarters by the consolidated interest charges for the same period. The cost of borrowing under DPL's revolving credit agreement and term loan adjust under certain credit rating scenarios. DPL’s revolving credit agreement, term loan, and senior unsecured notes due 2019 restrict dividend payments from DPL to AES. As of March 31, 2017 , DP&L and DPL were in compliance with all debt covenants, including the financial covenants described above. Substantially all property, plant & equipment of DP&L is subject to the lien of the mortgage securing DP&L’s First and Refunding Mortgage.
THE DAYTON POWER AND LIGHT COMPANY [Member]
Debt Instrument [Line Items]
Debt Obligations	Debt The following table provides a summary of DP&L's outstanding debt. Interest March 31, December 31, $ in millions Rate Maturity 2017 2016 Term loan - rates from 4.01% - 4.04% (a) and 4.00% - 4.01% (b) 2022 $ 443.9 $ 445.0 Tax-exempt First Mortgage Bonds 4.8% 2036 100.0 100.0 Tax-exempt First Mortgage Bonds - rates from 1.52% - 1.53% (a) and 1.29% - 1.42% (b) 2020 200.0 200.0 U.S. Government note 4.2% 2061 17.9 18.0 Capital leases 0.4 0.4 Unamortized deferred financing costs (11.5 ) (11.8 ) Unamortized debt discount (2.0 ) (2.2 ) Total long-term debt 748.7 749.4 Less: current portion (4.7 ) (4.7 ) Long-term debt, net of current portion $ 744.0 $ 744.7 (a) Range of interest rates for the three months ended March 31, 2017 . (b) Range of interest rates for the year ended December 31, 2016 . Premiums or discounts are amortized over the remaining life of the debt using the effective interest method. Debt covenants and restrictions DP&L’s unsecured revolving credit agreement and Bond Purchase and Covenants Agreement have two financial covenants. The first measures Total Debt to Total Capitalization and is calculated, at the end of each fiscal quarter, by dividing total debt at the end of the quarter by total capitalization at the end of the quarter. The second financial covenant measures EBITDA to Interest Expense and is calculated at the end of each fiscal quarter by dividing EBITDA for the four prior fiscal quarters by the consolidated interest charges for the same period. On February 21, 2017, DP&L and its lenders amended DP&L’s revolving credit agreement and Bond Purchase and Covenant Agreement. These amendments modified the definition of Consolidated Net Worth (which is used for measuring the Total Debt to Total Capitalization ratio under each of the agreements), to exclude, through March 31, 2018, non-cash charges related directly to impairments of coal generation assets in DP&L's fiscal quarter ending December 31, 2016 and thereafter. With this amendment, DP&L’s Total Debt to Total Capitalization ratio for the period ending March 31, 2017 is 0.53 to 1.00. The amendment also changed, for each amendment, the dates after generation separation during which compliance with the Total Capitalization ratio detailed above shall be suspended if long-term indebtedness, as determined by the PUCO, is less than or equal to $750.0 million . As noted above this time period previously was January 1, 2017 to December 31, 2017, and is now the twelve months immediately subsequent to the separation of the generation assets from DP&L . As of March 31, 2017 , DP&L was in compliance with all debt covenants, including the financial covenants described above. The cost of borrowing under DP&L's unsecured revolving credit agreement and Bond Purchase and Covenants Agreement adjusts under certain credit rating scenarios. Substantially all property, plant & equipment of DP&L is subject to the lien of the mortgage securing DP&L’s First and Refunding Mortgage.

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2017
Entity Information [Line Items]
Income Taxes	Income Taxes The following table details the effective tax rates for the three months ended March 31, 2017 and 2016 . Three months ended March 31, 2017 2016 DPL 37.9% 21.4% Income tax expense for the three months ended March 31, 2017 and 2016 was calculated using the estimated annual effective income tax rates for 2017 and 2016 of 37.6% and 20.6% , respectively. For the three months ended March 31, 2017 and 2016 , management estimated the annual effective tax rate based on its forecast of annual pre-tax income. To the extent that actual pre-tax results for the year differ from the forecasts applied to the most recent interim period, the rates estimated could be materially different from the actual effective tax rates. The increase in the annual effective rate compared to the same period in 2016 is primarily due to an increase of forecasted tax expense relating to flow-through depreciation and a reduction in the projected manufacturer's production deduction.
THE DAYTON POWER AND LIGHT COMPANY [Member]
Entity Information [Line Items]
Income Taxes	Income Taxes The following table details the effective tax rates for the three months ended March 31, 2017 and 2016 . Three months ended March 31, 2017 2016 DP&L 34.4% 26.9% Income tax expense for the three months ended March 31, 2017 and 2016 was calculated using the estimated annual effective income tax rates for 2017 and 2016 of 33.8% and 27.0% , respectively. For the three months ended March 31, 2017 and 2016 management estimated the annual effective tax rate based on its forecast of annual pre-tax income. To the extent that actual pre-tax results for the year differ from the forecasts applied to the most recent interim period, the rates estimated could be materially different from the actual effective tax rates. The increase in the annual effective rate compared to the same period in 2016 is primarily due to an increase of forecasted tax expense relating to flow-through depreciation and a reduction in the projected manufacturer's production deduction.

Benefit Plans

Benefit Plans	3 Months Ended
	Mar. 31, 2017
Entity Information [Line Items]
Pension and Postretirement Benefits	Benefit Plans DP&L sponsors a defined benefit pension plan for the vast majority of its employees. We generally fund pension plan benefits as accrued in accordance with the minimum funding requirements of ERISA and, in addition, make voluntary contributions from time to time. There were $5.0 million in employer contributions during each of the three months ended March 31, 2017 and 2016. The amounts presented in the following tables for pension include the collective bargaining plan formula, the traditional management plan formula, the cash balance plan formula and the SERP, in the aggregate. The pension costs below have not been adjusted for amounts billed to the Service Company for former DP&L employees who are now employed by the Service Company but are still participants in the DP&L plan. See Note 11 – Related Party Transactions . The net periodic benefit cost of the pension benefit plans for the three months ended March 31, 2017 and 2016 was: Net Periodic Benefit Cost Pension Three months ended March 31, $ in millions 2017 2016 Service cost $ 1.4 $ 1.4 Interest cost 3.6 3.7 Expected return on plan assets (5.7 ) (5.7 ) Plan curtailment (a) 4.1 — Amortization of unrecognized: Prior service cost 0.4 0.5 Actuarial loss 1.3 1.0 Net periodic benefit cost $ 5.1 $ 0.9 (a) As a result of the decision to retire certain of DP&L's coal-fired plants, we recognized a plan curtailment of $4.1 million in the first quarter of 2017. See Note 14 – Fixed-asset Impairment for more information. In addition, DP&L provides postretirement health care and life insurance benefits to certain retired employees, their spouses and eligible dependents. We have funded a portion of the union-eligible benefits using a Voluntary Employee Beneficiary Association Trust. These postretirement health care benefits and the related unfunded obligation of $15.8 million at both March 31, 2017 and December 31, 2016 were not material to the Financial Statements in the periods covered by this report. Benefit payments, which reflect future service, are estimated to be paid as follows: $ in millions Estimated to be paid during the twelve months ending March 31, Pension 2018 $ 18.8 2019 25.5 2020 26.0 2021 26.4 2022 26.7 2023 - 2027 139.6
THE DAYTON POWER AND LIGHT COMPANY [Member]
Entity Information [Line Items]
Pension and Postretirement Benefits	Benefit Plans DP&L sponsors a defined benefit pension plan for the vast majority of its employees. We generally fund pension plan benefits as accrued in accordance with the minimum funding requirements of ERISA and, in addition, make voluntary contributions from time to time. There were $5.0 million in employer contributions during each of the three months ended March 31, 2017 and 2016. The amounts presented in the following tables for pension include the collective bargaining plan formula, the traditional management plan formula, the cash balance plan formula and the SERP, in the aggregate. The pension costs below have not been adjusted for amounts billed to the Service Company for former DP&L employees who are now employed by the Service Company but are still participants in the DP&L plan. See Note 12 – Related Party Transactions . The net periodic benefit cost of the pension benefit plans for the three months ended March 31, 2017 and 2016 was: Net Periodic Benefit Cost Pension Three months ended March 31, $ in millions 2017 2016 Service cost $ 1.4 $ 1.4 Interest cost 3.6 3.7 Expected return on plan assets (5.7 ) (5.7 ) Plan curtailment (a) 5.6 — Amortization of unrecognized: Prior service cost 0.5 0.8 Actuarial loss 2.2 1.8 Net periodic benefit cost $ 7.6 $ 2.0 (a) As a result of the decision to retire certain of DP&L's coal-fired plants, we recognized a plan curtailment of $5.6 million in the first quarter of 2017. See Note 14 – Fixed-asset Impairment for more information. In addition, DP&L provides postretirement health care and life insurance benefits to certain retired employees, their spouses and eligible dependents. We have funded a portion of the union-eligible benefits using a Voluntary Employee Beneficiary Association Trust. These postretirement health care benefits and the related unfunded obligation of $15.8 million at both March 31, 2017 and December 31, 2016 were not material to the Financial Statements in the periods covered by this report. Benefit payments, which reflect future service, are estimated to be paid as follows: $ in millions Estimated to be paid during the twelve months ending March 31, Pension 2018 $ 18.8 2019 25.5 2020 26.0 2021 26.4 2022 26.7 2023 - 2027 139.6

Shareholder's Equity

Shareholder's Equity	3 Months Ended
	Mar. 31, 2017
THE DAYTON POWER AND LIGHT COMPANY [Member]
Class of Stock [Line Items]
Shareholder's Equity	Shareholder’s Equity DP&L has 250,000,000 authorized $0.01 par value common shares, of which 41,172,173 are outstanding at March 31, 2017 . All common shares are held by DP&L’s parent, DPL . As part of the PUCO’s approval of the Merger, DP&L agreed to maintain a capital structure that includes an equity ratio, calculated as total equity divided by total capitalization, of at least 50 percent and not to have a negative retained earnings balance. After the fixed-asset impairments recorded in 2017 and 2016 and as of March 31, 2017 , DP&L's equity ratio was 30% and retained earnings balance was negative. It is unknown what impact, if any, this will have on DP&L . In the generation separation order dated September 17, 2014, the PUCO permitted DP&L to temporarily maintain long-term debt of $750.0 million or 75% of its rate base, whichever is greater, until January 1, 2018.

Contractual Obligations, Commer

Contractual Obligations, Commercial Commitments and Contingencies	3 Months Ended
	Mar. 31, 2017
Entity Information [Line Items]
Contractual Obligations, Commercial Commitments and Contingencies	Contractual Obligations, Commercial Commitments and Contingencies Guarantees In the normal course of business, DPL enters into various agreements with its wholly-owned subsidiary, AES Ohio Generation , providing financial or performance assurance to third parties. These agreements are entered into primarily to support or enhance the creditworthiness otherwise attributed to this subsidiary on a stand-alone basis, thereby facilitating the extension of sufficient credit to accomplish these subsidiary's intended commercial purposes. At March 31, 2017 , DPL had $24.6 million of guarantees on behalf of AES Ohio Generation to third parties for future financial or performance assurance under such agreements. The guarantee arrangements entered into by DPL with these third parties cover select present and future obligations of AES Ohio Generation to such beneficiaries and are terminable by DPL upon written notice to the beneficiaries within a certain time. The carrying amount of obligations for commercial transactions covered by these guarantees recorded in our Condensed Consolidated Balance Sheets was $2.4 million and $2.3 million at March 31, 2017 and December 31, 2016 , respectively. To date, DPL has not incurred any losses related to the guarantees of AES Ohio Generation ’s obligations and we believe it is remote that DPL would be required to perform or incur any losses in the future associated with any of the above guarantees. Equity Ownership Interest DP&L owns a 4.9% equity ownership interest in OVEC, which is recorded using the cost method of accounting under GAAP. As of March 31, 2017 , DP&L could be responsible for the repayment of 4.9% , or $72.5 million , of a $1,479.6 million debt obligation that has maturities from 2018 to 2040 . This would happen if OVEC defaulted on debt payments. OVEC could also seek additional contributions from us to avoid a default in the event that other OVEC members defaulted on their OVEC repayment obligations. As of March 31, 2017 , we have no knowledge of such a default. Commercial Commitments and Contractual Obligations There have been no material changes, outside the ordinary course of business, to our commercial commitments and to the information disclosed in the contractual obligations table in our Form 10-K for the fiscal year ended December 31, 2016 . Contingencies In the normal course of business, we are subject to various lawsuits, actions, proceedings, claims and other matters asserted under various laws and regulations. We believe the amounts provided in our Condensed Consolidated Financial Statements, as prescribed by GAAP, are adequate in light of the probable and estimable contingencies. However, there can be no assurances that the actual amounts required to satisfy alleged liabilities from various legal proceedings, claims, tax examinations and other matters discussed below, and to comply with applicable laws and regulations, will not exceed the amounts reflected in our Condensed Consolidated Financial Statements. As such, costs, if any, that may be incurred in excess of those amounts provided as of March 31, 2017 , cannot be reasonably determined. Environmental Matters DPL’s and DP&L’s facilities and operations are subject to a wide range of federal, state and local environmental regulations and laws. The environmental issues that may affect us include: • The federal CAA and state laws and regulations (including State Implementation Plans) which require compliance, obtaining permits and reporting as to air emissions; • Litigation with federal and certain state governments and certain special interest groups regarding whether modifications to or maintenance of certain coal-fired generating stations require additional permitting or pollution control technology, or whether emissions from coal-fired generating stations cause or contribute to climate change; • Rules and future rules issued by the USEPA and the Ohio EPA that require or will require substantial reductions in SO 2 , particulates, mercury, acid gases, NOx, and other air emissions. DP&L has installed emission control technology and is taking other measures to comply with required and anticipated reductions; • Rules and future rules issued by the USEPA, the Ohio EPA or other authorities that require or will require reporting and reductions of GHGs; • Rules and future rules issued by the USEPA associated with the federal Clean Water Act, which prohibits the discharge of pollutants into waters of the United States except pursuant to appropriate permits; and • Solid and hazardous waste laws and regulations, which govern the management and disposal of certain waste. The majority of solid waste created from the combustion of coal and fossil fuels consists of fly ash and other coal combustion by-products.
THE DAYTON POWER AND LIGHT COMPANY [Member]
Entity Information [Line Items]
Contractual Obligations, Commercial Commitments and Contingencies	Contractual Obligations, Commercial Commitments and Contingencies Equity Ownership Interest DP&L owns a 4.9% equity ownership interest in OVEC, which is recorded using the cost method of accounting under GAAP. As of March 31, 2017 , DP&L could be responsible for the repayment of 4.9% , or $72.5 million , of a $1,479.6 million debt obligation that has maturities from 2018 to 2040 . This would happen if OVEC defaulted on debt payments. OVEC could also seek additional contributions from us to avoid a default in the event that other OVEC members defaulted on their OVEC repayment obligations. As of March 31, 2017 , we have no knowledge of such a default. Commercial Commitments and Contractual Obligations There have been no material changes, outside the ordinary course of business, to our commercial commitments and to the information disclosed in the contractual obligations table in our Form 10-K for the fiscal year ended December 31, 2016 . Contingencies In the normal course of business, we are subject to various lawsuits, actions, proceedings, claims and other matters asserted under various laws and regulations. We believe the amounts provided in our Condensed Financial Statements, as prescribed by GAAP, are adequate in light of the probable and estimable contingencies. However, there can be no assurances that the actual amounts required to satisfy alleged liabilities from various legal proceedings, claims, tax examinations and other matters discussed below, and to comply with applicable laws and regulations, will not exceed the amounts reflected in our Condensed Financial Statements. As such, costs, if any, that may be incurred in excess of those amounts provided as of March 31, 2017 , cannot be reasonably determined. Environmental Matters DP&L’s facilities and operations are subject to a wide range of federal, state and local environmental regulations and laws. The environmental issues that may affect us include: • The federal CAA and state laws and regulations (including State Implementation Plans) which require compliance, obtaining permits and reporting as to air emissions; • Litigation with federal and certain state governments and certain special interest groups regarding whether modifications to or maintenance of certain coal-fired generating stations require additional permitting or pollution control technology, or whether emissions from coal-fired generating stations cause or contribute to climate change; • Rules and future rules issued by the USEPA and the Ohio EPA that require or will require substantial reductions in SO 2 , particulates, mercury, acid gases, NOx, and other air emissions. DP&L has installed emission control technology and is taking other measures to comply with required and anticipated reductions; • Rules and future rules issued by the USEPA, the Ohio EPA or other authorities that require or will require reporting and reductions of GHGs; • Rules and future rules issued by the USEPA associated with the federal Clean Water Act, which prohibits the discharge of pollutants into waters of the United States except pursuant to appropriate permits; and • Solid and hazardous waste laws and regulations, which govern the management and disposal of certain waste. The majority of solid waste created from the combustion of coal and fossil fuels consists of fly ash and other coal combustion by-products.

Related Party Transactions

Related Party Transactions	3 Months Ended
	Mar. 31, 2017
Related Party Transaction [Line Items]
Related Party Transactions	Related Party Transactions Service Company The Service Company provides services including operations, accounting, legal, human resources, information technology and other corporate services on behalf of companies that are part of the U.S. SBU, including, among other companies, DPL and DP&L . The Service Company allocates the costs for these services based on cost drivers designed to result in fair and equitable allocations. This includes ensuring that the regulated utilities served, including DP&L , are not subsidizing costs incurred for the benefit of other businesses. Benefit plans DPL has an agreement with AES or one of its affiliates to participate in a group benefits program, including but not limited to, health, dental, vision and life benefits. AES or its affiliate administers the financial aspects of the group insurance program, receives all premium payments from the participating affiliates, and makes all vendor payments. The following table provides a summary of these transactions: Three months ended March 31, $ in millions 2017 2016 Transactions with the Service Company Charges for services provided $ 13.9 $ 11.6 Charges to the Service Company $ 1.0 $ 1.2 Transactions with other AES affiliates: Charges for health, welfare and benefit plans $ 4.2 $ 4.1 Balances with the Service Company: At March 31, 2017 At December 31, 2016 Net payable to the Service Company $ — $ (2.0 ) Net payable to other AES affiliates $ (3.1 ) $ (2.5 ) DPL Capital Trust II DPL has a wholly-owned business trust, DPL Capital Trust II (the "Trust"), formed for the purpose of issuing trust capital securities to third-party investors. Effective in 2003, DPL deconsolidated the Trust upon adoption of the accounting standards related to variable interest entities and currently treats the Trust as a nonconsolidated subsidiary. The Trust holds mandatorily redeemable trust capital securities. The investment in the Trust, which amounts to $0.3 million and $0.3 million at March 31, 2017 and December 31, 2016 , respectively, is included in Other deferred assets within Other non-current assets. DPL also has a note payable to the Trust amounting to $15.6 million and $15.6 million at March 31, 2017 and December 31, 2016 , respectively, that was established upon the Trust’s deconsolidation in 2003. See Note 7 – Debt for additional information. In addition to the obligations under the note payable mentioned above, DPL also agreed to a security obligation which represents a full and unconditional guarantee of payments to the capital security holders of the Trust. Income taxes AES files federal and state income tax returns which consolidate DPL and its subsidiaries. Under a tax sharing agreement with AES, DPL is responsible for the income taxes associated with its own taxable income and records the provision for income taxes using a separate return method. DPL had net payable balances of $70.6 million and $97.2 million at March 31, 2017 and December 31, 2016, respectively, which are recorded in Accrued taxes on the accompanying Balance Sheets on a gross basis.
THE DAYTON POWER AND LIGHT COMPANY [Member]
Related Party Transaction [Line Items]
Related Party Transactions	Related Party Transactions Service Company The Service Company provides services including operations, accounting, legal, human resources, information technology and other corporate services on behalf of companies that are part of the U.S. SBU, including, among other companies, DPL and DP&L . The Service Company allocates the costs for these services based on cost drivers designed to result in fair and equitable allocations. This includes ensuring that the regulated utilities served, including DP&L , are not subsidizing costs incurred for the benefit of other businesses. Benefit plans DPL has an agreement with AES or one of its affiliates to participate in a group benefits program, including but not limited to, health, dental, vision and life benefits. AES or its affiliate administers the financial aspects of the group insurance program, receives all premium payments from the participating affiliates, and makes all vendor payments. The following table provides a summary of these transactions: Three months ended March 31, $ in millions 2017 2016 DP&L Operation & Maintenance Expenses: Premiums paid for insurance services provided by MVIC (a) $ (0.8 ) $ (0.9 ) Transactions with the Service Company: Charges for services provided $ 13.0 $ 8.9 Charges to the Service Company $ 1.0 $ 1.2 Transactions with other AES affiliates: Charges for health, welfare and benefit plans $ 4.1 $ 4.1 Balances with related parties: At March 31, 2017 At December 31, 2016 Net payable to the Service Company $ — $ (2.0 ) Short-term loan with DPL (b) $ — $ 5.0 Net prepayment with / (payable to) other AES affiliates $ 5.0 $ (2.5 ) (a) MVIC, a wholly-owned captive insurance subsidiary of DPL , provides insurance coverage to DP&L and other DPL subsidiaries for workers’ compensation, general liability, property damages and directors’ and officers’ liability. These amounts represent insurance premiums paid by DP&L to MVIC. DP&L received insurance proceeds from MVIC of $0.0 million and $0.2 million for the three months ended March 31, 2017 and 2016, respectively. (b) On December 31, 2016, DPL loaned $5.0 million to DP&L through an intercompany short-term loan at 3.02% . Income taxes AES files federal and state income tax returns which consolidate DPL and its subsidiaries, including DP&L . Under a tax sharing agreement with DPL , DP&L is responsible for the income taxes associated with its own taxable income and records the provision for income taxes using a separate return method. DP&L had net receivable balances of $23.7 million and $9.5 million at March 31, 2017 and December 31, 2016, respectively, which are recorded in Accounts receivable, net on the accompanying Balance Sheets on a gross basis. Gain on termination of contract On January 1, 2016, DPL closed on the sale of DPLER. Also on January 1, 2016, DP&L terminated the contract it had with DPLER for the supply of electricity. The agreement terminating the contract was signed on December 28, 2015 and DP&L received $27.7 million of restricted cash on December 31, 2015 for the early termination of the contract. For the three months ended March 31, 2016, this amount was recorded in Gain on termination of contract in the Condensed Statements of Operations and the cash received was included in Cash flows from operating activities in the Condensed Statements of Cash Flows.

Business Segments

Business Segments	3 Months Ended
	Mar. 31, 2017
Segment Reporting Information [Line Items]
Business Segments	Business Segments During the fourth quarter of 2016, DPL's management reassessed the reportable business segments in connection with recent changes in the regulatory environment, including the pending ESP case, and in preparation for the anticipated transfer of DP&L’s generation assets to AES Ohio Generation. DPL currently manages the business through two reportable operating segments, the T&D segment and the Generation segment. The primary segment performance measure is income / (loss) from continuing operations before income tax as management has concluded that income / (loss) from continuing operations before income tax best reflects the underlying business performance of DPL and is the most relevant measure considered in DPL’s internal evaluation of the financial performance of its segments. The segments are discussed further below: Transmission and Distribution Segment The T&D segment is comprised primarily of DP&L’s electric transmission and distribution businesses, which distribute electricity to residential, commercial, industrial and governmental customers. DP&L distributes electricity to more than 520,000 retail customers who are located in a 6,000 square mile area of West Central Ohio. DP&L’s electric transmission and distribution businesses are subject to rate regulation by federal and state regulators. Accordingly, DP&L applies the accounting standards for regulated operations to its electric transmission and distribution businesses and records regulatory assets when incurred costs are expected to be recovered in future customer rates, and regulatory liabilities when current cost recoveries in customer rates relate to expected future costs. The T&D segment includes revenues and costs associated with our investment in OVEC and the historical results of DP&L’s Beckjord, Hutchings Coal, and East Bend generating facilities, which were either closed or sold in prior periods. As these assets will not be transferring to AES Ohio Generation when DP&L’s planned generation separation occurs, they are grouped with the T&D assets for segment reporting purposes. In addition, regulatory deferrals and collections, which include fuel deferrals in historical periods, are included in the T&D segment. Generation Segment The Generation segment is comprised of AES Ohio Generation and DP&L’s electric generation business. Beginning in 2001, Ohio law gave consumers the right to choose the electric generation supplier from whom they purchase retail generation services. AES Ohio Generation owns and operates peaking generating facilities, and DP&L owns multiple coal-fired and peaking electric generating facilities. Both AES Ohio Generation and DP&L primarily sell their generated energy and capacity into the PJM wholesale market as DP&L sources all of the generation for its SSO customers through a competitive bid process. Included within the “Other” column are other businesses that do not meet the GAAP requirements for disclosure as reportable segments as well as certain corporate costs, which include interest expense on DPL’s debt and adjustments related to purchase accounting from the Merger. The accounting policies of the reportable segments are the same as those described in Note 1 – Overview and Summary of Significant Accounting Policies. Intersegment sales and profits are eliminated in consolidation. Certain shared and corporate costs are allocated among reporting segments. The following tables present financial information for each of DPL’s reportable business segments: $ in millions T&D Generation Other Adjustments and Eliminations DPL Consolidated Three months ended March 31, 2017 Revenues from external customers $ 189.8 $ 131.8 $ 2.3 $ — $ 323.9 Intersegment revenues 0.3 — 1.4 (1.7 ) — Total revenues $ 190.1 $ 131.8 $ 3.7 $ (1.7 ) $ 323.9 Depreciation and amortization $ 18.1 $ 7.0 $ 2.9 $ — $ 28.0 Fixed-asset impairment (Note 14) $ — $ 66.3 $ 0.1 $ — $ 66.4 Interest expense $ 7.4 $ — $ 19.6 $ (0.1 ) $ 26.9 Income / (loss) from continuing operations before income tax $ 25.0 $ (86.8 ) $ (21.4 ) $ — $ (83.2 ) Cash capital expenditures $ 26.3 $ 14.1 $ 1.0 $ — $ 41.4 At March 31, 2017 Total assets $ 1,680.9 $ 366.1 $ 633.6 $ (416.4 ) $ 2,264.2 $ in millions T&D Generation Other Adjustments and Eliminations DPL Consolidated Three months ended March 31, 2016 Revenues from external customers $ 204.2 $ 158.2 $ 1.6 $ — $ 364.0 Intersegment revenues 0.3 — 1.3 (1.6 ) — Total revenues $ 204.5 $ 158.2 $ 2.9 $ (1.6 ) $ 364.0 Depreciation and amortization $ 17.2 $ 18.6 $ (2.4 ) $ — $ 33.4 Interest expense $ 5.4 $ 0.1 $ 20.9 $ (0.1 ) $ 26.3 Income / (loss) from continuing operations before income tax $ 34.2 $ (12.3 ) $ (19.1 ) $ — $ 2.8 Cash capital expenditures $ 24.1 $ 13.0 $ 0.6 $ — $ 37.7 At December 31, 2016 Total assets $ 1,710.5 $ 472.3 $ 673.6 $ (437.2 ) $ 2,419.2
Subsidiaries [Member]
Segment Reporting Information [Line Items]
Business Segments	Business Segments During the fourth quarter of 2016, DP&L’s management reassessed the separate reportable business segments in connection with recent changes in the regulatory environment, including the pending ESP case, and in preparation for the anticipated transfer of DP&L’s generation assets to AES Ohio Generation. DP&L currently manages the business through two reportable operating segments, the T&D segment and the Generation segment. The primary segment performance measure is income / (loss) from operations before income tax as management has concluded that income / (loss) from operations before income tax best reflects the underlying business performance of DP&L and is the most relevant measure considered in DP&L’s internal evaluation of the financial performance of its segments. The segments are discussed further below: Transmission and Distribution Segment The T&D segment is comprised primarily of DP&L’s electric transmission and distribution businesses, which distribute electricity to residential, commercial, industrial and governmental customers. DP&L distributes electricity to more than 520,000 retail customers who are located in a 6,000 square mile area of West Central Ohio. DP&L’s electric transmission and distribution businesses are subject to rate regulation by federal and state regulators. Accordingly, DP&L applies the accounting standards for regulated operations to its electric transmission and distribution businesses and records regulatory assets when incurred costs are expected to be recovered in future customer rates, and regulatory liabilities when current cost recoveries in customer rates relate to expected future costs. The T&D segment includes revenues and costs associated with our investment in OVEC and the historical results of DP&L’s Beckjord, Hutchings Coal, and East Bend generating facilities, which were either closed or sold in prior periods. As these assets will not be transferring to AES Ohio Generation when DP&L’s planned generation separation occurs, they are grouped with the T&D assets for segment reporting purposes. In addition, regulatory deferrals and collections, which include fuel deferrals in historical periods, are included in the T&D segment. Generation Segment The Generation segment is comprised of DP&L’s electric generation business. Beginning in 2001, Ohio law gave consumers the right to choose the electric generation supplier from whom they purchase retail generation services. DP&L's generation segment owns multiple coal-fired and peaking electric generating facilities. DP&L's generation segment sells its generated energy and capacity into the wholesale market as DP&L sources all of the generation for its SSO customers through a competitive bid process. The accounting policies of the reportable segments are the same as those described in Note 1 – Overview and Summary of Significant Accounting Policies. Intersegment sales and profits are eliminated in consolidation. Certain shared and corporate costs are allocated among reporting segments. The following tables present financial information for each of DP&L’s reportable business segments: $ in millions T&D Generation Adjustments and Eliminations DP&L Total Three months ended March 31, 2017 Revenues from external customers $ 190.1 $ 121.0 $ — $ 311.1 Intersegment revenues — — — — Total revenues $ 190.1 $ 121.0 $ — $ 311.1 Depreciation and amortization $ 18.1 $ 5.4 $ — $ 23.5 Fixed-asset impairment (Note 14) $ — $ 66.3 $ — $ 66.3 Interest expense $ 7.4 $ 0.2 $ — $ 7.6 Income / (loss) from operations before income tax $ 25.0 $ (88.7 ) $ — $ (63.7 ) Cash capital expenditures $ 26.3 $ 7.8 $ — $ 34.1 At March 31, 2017 Total assets $ 1,680.9 $ 209.0 $ — $ 1,889.9 $ in millions T&D Generation Adjustments and Eliminations DP&L Total Three months ended March 31, 2016 Revenues from external customers $ 204.5 $ 144.7 $ — $ 349.2 Intersegment revenues — — — — Total revenues $ 204.5 $ 144.7 $ — $ 349.2 Depreciation and amortization $ 17.2 $ 17.1 $ — $ 34.3 Interest expense $ 5.2 $ 0.1 $ — $ 5.3 Income from operations before income tax $ 34.4 $ 11.7 $ — $ 46.1 Cash capital expenditures $ 24.1 $ 11.7 $ — $ 35.8 At December 31, 2016 Total assets $ 1,710.5 $ 324.6 $ — $ 2,035.1

Discontinued Operations

Discontinued Operations	3 Months Ended
	Mar. 31, 2017
Discontinued Operations and Disposal Groups [Abstract]
Discontinued Operations	Discontinued Operations On January 1, 2016, DPL closed on the sale of DPLER, its competitive retail business. The sale agreement was signed on December 28, 2015 and DPL received $75.5 million of restricted cash on December 31, 2015 for the sale. DPL recorded a gain on this transaction of $49.2 million in the first quarter of 2016. The gain includes the impact of DPLER’s liability to DP&L that transferred with the sale on January 1, 2016 but was eliminated in consolidation as of December 31, 2015. Operating activities related to DPLER have been reclassified to "Discontinued operations" in the Condensed Consolidated Statements of Operations for the three months ended March 31, 2016. The following table summarizes the revenues, cost of revenues, operating expenses and income tax of discontinued operations for the periods indicated: Three months ended $ in millions 2016 Revenues $ — Cost of revenues — Operating expenses (0.7 ) Loss from discontinued operations before income taxes (0.7 ) Gain from disposal of discontinued operations 49.2 Income tax expense 18.9 Income on discontinued operations $ 29.6 Cash flows related to discontinued operations are included in our Condensed Consolidated Statements of Cash Flows. Cash flows from operating activities for discontinued operations were $(0.7) million for the three months ended March 31, 2016 . Cash flows from investing activities for discontinued operations were $75.5 million for the three months ended March 31, 2016 . All cash generated from discontinued operations was paid to DPL through dividends for all periods presented.

Fixed-asset Impairment (Notes)

Fixed-asset Impairment (Notes)	3 Months Ended
	Mar. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Asset Impairment Charges [Text Block]	Fixed-asset Impairment On March 17, 2017, the Board of Directors of DP&L approved the retirement of the DP&L operated and co-owned Stuart Station coal-fired and diesel-fired generating units and the Killen Station coal-fired generating unit and combustion turbine (collectively, the “Facilities”) on or before June 1, 2018. DP&L also reached agreement with the co-owners of the Facilities to proceed with this plan of retirement. We performed a long-lived asset impairment analysis and determined that the carrying amounts of the Facilities were not recoverable. The asset groups of Stuart Station and Killen Station were determined to have fair values of $3.3 million and $7.9 million , respectively, using the discounted cash flows under the income approach. As a result, we recognized an asset impairment expense of $39.1 million and $27.3 million for Stuart Station and Killen Station, respectively. Additionally, as a result of the decision to retire the Facilities by June 1, 2018, we concluded that inventory at these Facilities is considered obsolete. As a result, we recognized a loss on disposal of $9.8 million and $6.4 million for Stuart Station and Killen Station inventories, respectively, during the first quarter of 2017, which is recorded in Loss on asset disposal in the Condensed Consolidated Statements of Operations.
THE DAYTON POWER AND LIGHT COMPANY [Member]
Finite-Lived Intangible Assets [Line Items]
Asset Impairment Charges [Text Block]	Fixed-asset Impairment On March 17, 2017, the Board of Directors of DP&L approved the retirement of the DP&L operated and co-owned Stuart Station coal-fired and diesel-fired generating units and the Killen Station coal-fired generating unit and combustion turbine (collectively, the “Facilities”) on or before June 1, 2018. DP&L also reached agreement with the co-owners of the Facilities to proceed with this plan of retirement. We performed a long-lived asset impairment analysis and determined that the carrying amounts of the Facilities were not recoverable. The asset groups of Stuart Station and Killen Station were determined to have fair values of $3.3 million and $7.9 million , respectively, using the discounted cash flows under the income approach. As a result, we recognized an asset impairment expense of $39.0 million and $27.3 million for Stuart Station and Killen Station, respectively. Additionally, as a result of the decision to retire the Facilities by June 1, 2018, we concluded that inventory at these Facilities is considered obsolete. As a result, we recognized a loss on disposal of $9.8 million and $6.4 million for Stuart Station and Killen Station inventories, respectively, during the first quarter of 2017, which is recorded in Loss on asset disposal in the Condensed Statements of Operations.

Summary of Significant Accounti

Summary of Significant Accounting Policies (Policy)	3 Months Ended
	Mar. 31, 2017
Significant Accounting Policies [Line Items]
Description of Business	Description of Business DPL is a diversified regional energy company organized in 1985 under the laws of Ohio. DPL has two reportable segments: the Transmission and Distribution (T&D) segment and the Generation segment. See Note 12 – Business Segments for more information relating to these reportable segments. The terms “we,” “us,” “our” and “ours” are used to refer to DPL and its subsidiaries. DPL is an indirectly wholly-owned subsidiary of AES. DP&L is a public utility incorporated in 1911 under the laws of Ohio. Beginning in 2001, Ohio law gave Ohio consumers the right to choose the electric generation supplier from whom they purchase retail generation service; however, distribution and transmission retail services are still regulated. DP&L has the exclusive right to provide such distribution and transmission services to approximately 520,000 customers located in West Central Ohio. Additionally, DP&L offers retail SSO electric service to residential, commercial, industrial and governmental customers in a 6,000 square mile area of West Central Ohio. DP&L owns multiple coal-fired and peaking electric generating facilities as well as numerous transmission facilities, all of which are included in the financial statements at amortized cost. DP&L sources 100% of the generation for its SSO customers through a competitive bid process. Principal industries located in DP&L’s service territory include automotive, food processing, paper, plastic, manufacturing and defense. DP&L's distribution sales reflect the general economic conditions, seasonal weather patterns, retail competition in our service territory and the market price of electricity. DP&L sells all of its energy and capacity into the wholesale market. DPL’s other significant subsidiaries include AES Ohio Generation, which owns and operates peaking generating facilities from which it sells all of its energy and capacity into the wholesale market, and MVIC, our captive insurance company that provides insurance services to DPL and our subsidiaries. DPL owns all of the common stock of its subsidiaries. DPL also has a wholly-owned business trust, DPL Capital Trust II, formed for the purpose of issuing trust capital securities to investors. DP&L’s electric transmission and distribution businesses are subject to rate regulation by federal and state regulators while its generation business is deemed competitive under Ohio law. Accordingly, DP&L applies the accounting standards for regulated operations to its electric transmission and distribution businesses and records regulatory assets when incurred costs are expected to be recovered in future customer rates, and regulatory liabilities when current cost recoveries in customer rates relate to expected future costs. DPL and its subsidiaries employed 1,153 people as of March 31, 2017 , of which 1,145 were employed by DP&L . Approximately 62% of all DPL employees are under a collective bargaining agreement that expires on October 31, 2017 .
Financial Statement Presentation	Financial Statement Presentation DPL’s Condensed Consolidated Financial Statements include the accounts of DPL and its wholly-owned subsidiaries except for DPL Capital Trust II, which is not consolidated, consistent with the provisions of GAAP. DP&L has undivided ownership interests in five coal-fired generating facilities, various peaking generating facilities and numerous transmission facilities, all of which are included in the financial statements at amortized cost, which was adjusted to fair value at the date of the Merger for DPL . Operating revenues and expenses of these facilities are included on a pro rata basis in the corresponding lines in the Condensed Consolidated Statements of Operations. Certain immaterial amounts from prior periods have been reclassified to conform to the current period presentation. All material intercompany accounts and transactions are eliminated in consolidation. These financial statements have been prepared in accordance with GAAP for interim financial statements, the instructions of Form 10-Q and Regulation S-X. Accordingly, certain information and footnote disclosures normally included in the annual financial statements prepared in accordance with GAAP have been omitted from this interim report. Therefore, our interim financial statements in this report should be read along with the annual financial statements included in our Form 10-K for the fiscal year ended December 31, 2016 . In the opinion of our management, the Condensed Consolidated Financial Statements presented in this report contain all adjustments necessary to fairly state our financial position as of March 31, 2017 ; our results of operations for the three months ended March 31, 2017 and 2016 and our cash flows for the three months ended March 31, 2017 and 2016 . Unless otherwise noted, all adjustments are normal and recurring in nature. Due to various factors, including, but not limited to, seasonal weather variations, the timing of outages of EGUs, changes in economic conditions involving commodity prices and competition, and other factors, interim results for the three months ended March 31, 2017 may not be indicative of our results that will be realized for the full year ending December 31, 2017 . The preparation of financial statements in conformity with GAAP requires us to make estimates and judgments that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities, and the revenues and expenses of the periods reported. Actual results could differ from these estimates. Significant items subject to such estimates and judgments include: the carrying value of property, plant and equipment; unbilled revenues; the valuation of derivative instruments; the valuation of insurance and claims liabilities; the valuation of allowances for receivables and deferred income taxes; regulatory assets and liabilities; liabilities recorded for income tax exposures; litigation; contingencies; the valuation of AROs; and assets and liabilities related to employee benefits.
Accounting for Taxes Collected from Customers and Remitted to Governmental Authorities	Accounting for Taxes Collected from Customers and Remitted to Governmental Authorities DP&L collects certain excise taxes levied by state or local governments from its customers. These taxes are accounted for on a net basis and not included in revenue. The amounts of such taxes collected for the three months ended March 31, 2017 and 2016 were $12.5 million and $12.9 million, respectively.
Recently Issued Accounting Standards	New Accounting Pronouncements The following table provides a brief description of recent accounting pronouncements that could have a material impact on our consolidated financial statements: Accounting Standard Description Date of Adoption Effect on the financial statements upon adoption New Accounting Standards Adopted 2016-09, Compensation - Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting The standard simplifies the following aspects of accounting for share-based payments awards: accounting for income taxes, classification of excess tax benefits on the statement of cash flows, forfeitures, statutory tax withholding requirements, classification of awards as either equity or liabilities and classification of employee taxes paid on statement of cash flows when an employer withholds shares for tax-withholding purposes. Transition method: The recognition of excess tax benefits and tax deficiencies arising from vesting or settlement were applied retrospectively. The elimination of the requirement that excess tax benefits be realized before they are recognized was adopted on a modified retrospective basis with a cumulative adjustment to the opening balance sheet. January 1, 2017 The primary effect of adoption was the recognition of excess tax benefits in our provision for income taxes in the period when the awards vest or are settled, rather than in paid-in-capital in the period when the excess tax benefits are realized. We will continue to estimate the number of awards that are expected to vest in our determination of the related periodic compensation cost. The adoption of this standard did not have a material impact on the consolidated financial statements. Accounting Standard Description Date of Adoption Effect on the financial statements upon adoption New Accounting Standards Issued But Not Yet Effective 2017-08, Receivables - Nonrefundable Fees and Other Costs (Subtopic 310-20): Premium Amortization on Purchased Callable Debt Securities This standard shortens the period of amortization of the premium on certain callable debt securities to the earliest call date. January 1, 2019. We are currently evaluating the impact of adopting the standard on our consolidated financial statements. 2017-07, Compensation—Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost The standard provides guidance on the presentation of net benefit cost in an employer’s income statement and on the components eligible for capitalization. It requires that an employer report the service cost component in the same line item(s) as other employee compensation costs arising from services rendered during the period, and report the other components of net benefit cost separately from the service cost component and outside a subtotal of operating income. Only the service cost component will be eligible for capitalization. January 1, 2018. Early adoption is permitted. We are currently evaluating the impact of adopting the standard on our consolidated financial statements. 2017-01, Business Combinations (Topic 805): Clarifying the Definition of a Business This standard provides guidance to assist the entities with evaluating when a set of transferred assets and activities is a business. January 1, 2018. Early adoption is permitted We are currently evaluating the impact of adopting the standard on our consolidated financial statements. 2016-18, Statement of Cash Flows (Topic 320): Restricted Cash (a consensus of the FASB Emerging Issues Task Force) This standard requires that a statement of cash flows explain the change during the period in the total of cash, cash equivalents, and amounts generally described as restricted cash or restricted cash equivalents. Therefore, amounts generally described as restricted cash and restricted cash equivalents should be included with cash and cash equivalents when reconciling the beginning-of-period and end-of-period total amounts shown on the statement of cash flows. January 1, 2018. Early adoption is permitted We are currently evaluating the impact of adopting the standard on our consolidated financial statements. 2016-16, Income Taxes (Topic 740): Intra-Entity Transfers of Assets Other Than Inventory This standard requires that an entity recognizes the income tax consequences of an intra-entity transfer of an asset other than inventory when the transfer occurs. January 1, 2018. Early adoption is permitted. We are currently evaluating the impact of adopting the standard on our consolidated financial statements. 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Receipts and Cash Payments (a consensus of the Emerging Issues Task Force) This standard provides specific guidance on how certain cash transactions are presented and classified in the statement of cash flows. January 1, 2018. Early adoption is permitted. We are currently evaluating the impact of adopting the standard on our consolidated financial statements but do not anticipate a material impact. 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments This standard updates the impairment model for financial assets measured at amortized cost to an expected loss model rather than an incurred loss model. It also allows for the presentation of credit losses on available-for-sale debt securities as an allowance rather than a write down. January 1, 2020. Early adoption is permitted only as of January 1, 2019. We are currently evaluating the impact of adopting the standard on our consolidated financial statements. 2016-02, Leases (Topic 842) The standard creates Topic 842, Leases which supersedes Topic 840, Leases, and introduces a lessee model that brings substantially all leases onto the balance sheet while retaining most of the principles of the existing lessor model in U.S. GAAP and aligning many of those principles with ASC 606, Revenue from Contracts with Customers. January 1, 2019. Early adoption is permitted. We are currently evaluating the impact of adopting the standard on our consolidated financial statements. Accounting Standard Description Date of Adoption Effect on the financial statements upon adoption 2014-09, 2015-14, 2016-08, 2016-10, 2016-12, 2016-20, 2017-05 Revenue from Contracts with Customers (Topic 606) See discussion of the ASUs below. January 1, 2018. Earlier application is permitted only as of January 1, 2017. We will adopt the standard on January 1, 2018; see below for the evaluation of the impact of its adoption on the consolidated financial statements.
THE DAYTON POWER AND LIGHT COMPANY [Member]
Significant Accounting Policies [Line Items]
Description of Business	Description of Business DP&L is a public utility incorporated in 1911 under the laws of Ohio. Beginning in 2001, Ohio law gave Ohio consumers the right to choose the electric generation supplier from whom they purchase retail generation service; however, distribution and transmission retail services are still regulated. DP&L has the exclusive right to provide such distribution and transmission services to approximately 520,000 customers located in West Central Ohio. Additionally, DP&L offers retail SSO electric service to residential, commercial, industrial and governmental customers in a 6,000 square mile area of West Central Ohio. DP&L owns multiple coal-fired and peaking electric generating facilities as well as numerous transmission facilities, all of which are included in the financial statements at amortized cost. DP&L sources 100% of the generation for its SSO customers through a competitive bid process. Principal industries located in DP&L’s service territory include automotive, food processing, paper, plastic, manufacturing and defense. DP&L's distribution sales reflect the general economic conditions, seasonal weather patterns, retail competition in our service territory and the market price of electricity. DP&L sells all of its energy and capacity into the wholesale market. DP&L is a subsidiary of DPL . DP&L has two reportable segments: the Transmission and Distribution (T&D) segment and the Generation segment. See Note 13 – Business Segments for more information relating to these reportable segments. DP&L’s electric transmission and distribution businesses are subject to rate regulation by federal and state regulators while its generation business is deemed competitive under Ohio law. Accordingly, DP&L applies the accounting standards for regulated operations to its electric transmission and distribution businesses and records regulatory assets when incurred costs are expected to be recovered in future customer rates, and regulatory liabilities when current cost recoveries in customer rates relate to expected future costs. DP&L employed 1,145 people as of March 31, 2017 . Approximately 62% of all employees are under a collective bargaining agreement which expires on October 31, 2017 .
Financial Statement Presentation	Financial Statement Presentation DP&L does not have any subsidiaries. DP&L has undivided ownership interests in five coal-fired generating facilities, peaking electric generating facilities and numerous transmission facilities, all of which are included in the financial statements at amortized cost. Operating revenues and expenses of these facilities are included on a pro rata basis in the corresponding lines in the Condensed Statements of Operations. Certain immaterial amounts from prior periods have been reclassified to conform to the current period presentation. These financial statements have been prepared in accordance with GAAP for interim financial statements, the instructions of Form 10-Q and Regulation S-X. Accordingly, certain information and footnote disclosures normally included in the annual financial statements prepared in accordance with GAAP have been omitted from this interim report. Therefore, our interim financial statements in this report should be read along with the annual financial statements included in our Form 10-K for the fiscal year ended December 31, 2016 . In the opinion of our management, the Condensed Financial Statements presented in this report contain all adjustments necessary to fairly state our financial position as of March 31, 2017 ; our results of operations for the three months ended March 31, 2017 and 2016 and our cash flows for the three months ended March 31, 2017 and 2016 . Unless otherwise noted, all adjustments are normal and recurring in nature. Due to various factors, including, but not limited to, seasonal weather variations, the timing of outages of EGUs, changes in economic conditions involving commodity prices and competition, and other factors, interim results for the three months ended March 31, 2017 may not be indicative of our results that will be realized for the full year ending December 31, 2017 . The preparation of financial statements in conformity with GAAP requires us to make estimates and judgments that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities, and the revenues and expenses of the periods reported. Actual results could differ from these estimates. Significant items subject to such estimates and judgments include: the carrying value of property, plant and equipment; unbilled revenues; the valuation of derivative instruments; the valuation of insurance and claims liabilities; the valuation of allowances for receivables and deferred income taxes; regulatory assets and liabilities; liabilities recorded for income tax exposures; litigation; contingencies; the valuation of AROs; and assets and liabilities related to employee benefits.
Accounting for Taxes Collected from Customers and Remitted to Governmental Authorities	Accounting for Taxes Collected from Customers and Remitted to Governmental Authorities DP&L collects certain excise taxes levied by state or local governments from its customers. These taxes are accounted for on a net basis and not included in revenue. The amounts of such taxes collected for the three months ended March 31, 2017 and 2016 were $12.5 million and $12.9 million, respectively.
Recently Issued Accounting Standards	New Accounting Pronouncements The following table provides a brief description of recent accounting pronouncements that could have a material impact on our financial statements: Accounting Standard Description Date of Adoption Effect on the financial statements upon adoption New Accounting Standards Adopted 2016-09, Compensation - Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting The standard simplifies the following aspects of accounting for share-based payments awards: accounting for income taxes, classification of excess tax benefits on the statement of cash flows, forfeitures, statutory tax withholding requirements, classification of awards as either equity or liabilities and classification of employee taxes paid on statement of cash flows when an employer withholds shares for tax-withholding purposes. Transition method: The recognition of excess tax benefits and tax deficiencies arising from vesting or settlement were applied retrospectively. The elimination of the requirement that excess tax benefits be realized before they are recognized was adopted on a modified retrospective basis with a cumulative adjustment to the opening balance sheet. January 1, 2017 The primary effect of adoption was the recognition of excess tax benefits in our provision for income taxes in the period when the awards vest or are settled, rather than in paid-in-capital in the period when the excess tax benefits are realized. We will continue to estimate the number of awards that are expected to vest in our determination of the related periodic compensation cost. The adoption of this standard did not have a material impact on the financial statements. New Accounting Standards Issued But Not Yet Effective 2017-08, Receivables - Nonrefundable Fees and Other Costs (Subtopic 310-20): Premium Amortization on Purchased Callable Debt Securities This standard shortens the period of amortization of the premium on certain callable debt securities to the earliest call date. January 1, 2019. We are currently evaluating the impact of adopting the standard on our financial statements. 2017-07, Compensation—Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost The standard provides guidance on the presentation of net benefit cost in an employer’s income statement and on the components eligible for capitalization. It requires that an employer report the service cost component in the same line item(s) as other employee compensation costs arising from services rendered during the period, and report the other components of net benefit cost separately from the service cost component and outside a subtotal of operating income. Only the service cost component will be eligible for capitalization. January 1, 2018. Early adoption is permitted. We are currently evaluating the impact of adopting the standard on our financial statements. 2017-01, Business Combinations (Topic 805): Clarifying the Definition of a Business This standard provides guidance to assist the entities with evaluating when a set of transferred assets and activities is a business. January 1, 2018. Early adoption is permitted We are currently evaluating the impact of adopting the standard on our financial statements. Accounting Standard Description Date of Adoption Effect on the financial statements upon adoption 2016-18, Statement of Cash Flows (Topic 320): Restricted Cash (a consensus of the FASB Emerging Issues Task Force) This standard requires that a statement of cash flows explain the change during the period in the total of cash, cash equivalents, and amounts generally described as restricted cash or restricted cash equivalents. Therefore, amounts generally described as restricted cash and restricted cash equivalents should be included with cash and cash equivalents when reconciling the beginning-of-period and end-of-period total amounts shown on the statement of cash flows. January 1, 2018. Early adoption is permitted We are currently evaluating the impact of adopting the standard on our financial statements. 2016-16, Income Taxes (Topic 740): Intra-Entity Transfers of Assets Other Than Inventory This standard requires that an entity recognizes the income tax consequences of an intra-entity transfer of an asset other than inventory when the transfer occurs. January 1, 2018. Early adoption is permitted. We are currently evaluating the impact of adopting the standard on our financial statements. 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Receipts and Cash Payments (a consensus of the Emerging Issues Task Force) This standard provides specific guidance on how certain cash transactions are presented and classified in the statement of cash flows. January 1, 2018. Early adoption is permitted. We are currently evaluating the impact of adopting the standard on our financial statements but do not anticipate a material impact. 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments This standard updates the impairment model for financial assets measured at amortized cost to an expected loss model rather than an incurred loss model. It also allows for the presentation of credit losses on available-for-sale debt securities as an allowance rather than a write down. January 1, 2020. Early adoption is permitted only as of January 1, 2019. We are currently evaluating the impact of adopting the standard on our financial statements. 2016-02, Leases (Topic 842) The standard creates Topic 842, Leases which supersedes Topic 840, Leases, and introduces a lessee model that brings substantially all leases onto the balance sheet while retaining most of the principles of the existing lessor model in U.S. GAAP and aligning many of those principles with ASC 606, Revenue from Contracts with Customers. January 1, 2019. Early adoption is permitted. We are currently evaluating the impact of adopting the standard on our financial statements. 2014-09, 2015-14, 2016-08, 2016-10, 2016-12, 2016-20, 2017-05 Revenue from Contracts with Customers (Topic 606) See discussion of the ASUs below. January 1, 2018. Earlier application is permitted only as of January 1, 2017. We will adopt the standard on January 1, 2018; see below for the evaluation of the impact of its adoption on the financial statements.

Summary of Significant Accoun24

Summary of Significant Accounting Policies (Tables)	3 Months Ended
	Mar. 31, 2017
Related Party Transaction [Line Items]
Schedule of New Accounting Pronouncements	The following table provides a brief description of recent accounting pronouncements that could have a material impact on our consolidated financial statements: Accounting Standard Description Date of Adoption Effect on the financial statements upon adoption New Accounting Standards Adopted 2016-09, Compensation - Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting The standard simplifies the following aspects of accounting for share-based payments awards: accounting for income taxes, classification of excess tax benefits on the statement of cash flows, forfeitures, statutory tax withholding requirements, classification of awards as either equity or liabilities and classification of employee taxes paid on statement of cash flows when an employer withholds shares for tax-withholding purposes. Transition method: The recognition of excess tax benefits and tax deficiencies arising from vesting or settlement were applied retrospectively. The elimination of the requirement that excess tax benefits be realized before they are recognized was adopted on a modified retrospective basis with a cumulative adjustment to the opening balance sheet. January 1, 2017 The primary effect of adoption was the recognition of excess tax benefits in our provision for income taxes in the period when the awards vest or are settled, rather than in paid-in-capital in the period when the excess tax benefits are realized. We will continue to estimate the number of awards that are expected to vest in our determination of the related periodic compensation cost. The adoption of this standard did not have a material impact on the consolidated financial statements. Accounting Standard Description Date of Adoption Effect on the financial statements upon adoption New Accounting Standards Issued But Not Yet Effective 2017-08, Receivables - Nonrefundable Fees and Other Costs (Subtopic 310-20): Premium Amortization on Purchased Callable Debt Securities This standard shortens the period of amortization of the premium on certain callable debt securities to the earliest call date. January 1, 2019. We are currently evaluating the impact of adopting the standard on our consolidated financial statements. 2017-07, Compensation—Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost The standard provides guidance on the presentation of net benefit cost in an employer’s income statement and on the components eligible for capitalization. It requires that an employer report the service cost component in the same line item(s) as other employee compensation costs arising from services rendered during the period, and report the other components of net benefit cost separately from the service cost component and outside a subtotal of operating income. Only the service cost component will be eligible for capitalization. January 1, 2018. Early adoption is permitted. We are currently evaluating the impact of adopting the standard on our consolidated financial statements. 2017-01, Business Combinations (Topic 805): Clarifying the Definition of a Business This standard provides guidance to assist the entities with evaluating when a set of transferred assets and activities is a business. January 1, 2018. Early adoption is permitted We are currently evaluating the impact of adopting the standard on our consolidated financial statements. 2016-18, Statement of Cash Flows (Topic 320): Restricted Cash (a consensus of the FASB Emerging Issues Task Force) This standard requires that a statement of cash flows explain the change during the period in the total of cash, cash equivalents, and amounts generally described as restricted cash or restricted cash equivalents. Therefore, amounts generally described as restricted cash and restricted cash equivalents should be included with cash and cash equivalents when reconciling the beginning-of-period and end-of-period total amounts shown on the statement of cash flows. January 1, 2018. Early adoption is permitted We are currently evaluating the impact of adopting the standard on our consolidated financial statements. 2016-16, Income Taxes (Topic 740): Intra-Entity Transfers of Assets Other Than Inventory This standard requires that an entity recognizes the income tax consequences of an intra-entity transfer of an asset other than inventory when the transfer occurs. January 1, 2018. Early adoption is permitted. We are currently evaluating the impact of adopting the standard on our consolidated financial statements. 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Receipts and Cash Payments (a consensus of the Emerging Issues Task Force) This standard provides specific guidance on how certain cash transactions are presented and classified in the statement of cash flows. January 1, 2018. Early adoption is permitted. We are currently evaluating the impact of adopting the standard on our consolidated financial statements but do not anticipate a material impact. 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments This standard updates the impairment model for financial assets measured at amortized cost to an expected loss model rather than an incurred loss model. It also allows for the presentation of credit losses on available-for-sale debt securities as an allowance rather than a write down. January 1, 2020. Early adoption is permitted only as of January 1, 2019. We are currently evaluating the impact of adopting the standard on our consolidated financial statements. 2016-02, Leases (Topic 842) The standard creates Topic 842, Leases which supersedes Topic 840, Leases, and introduces a lessee model that brings substantially all leases onto the balance sheet while retaining most of the principles of the existing lessor model in U.S. GAAP and aligning many of those principles with ASC 606, Revenue from Contracts with Customers. January 1, 2019. Early adoption is permitted. We are currently evaluating the impact of adopting the standard on our consolidated financial statements. Accounting Standard Description Date of Adoption Effect on the financial statements upon adoption 2014-09, 2015-14, 2016-08, 2016-10, 2016-12, 2016-20, 2017-05 Revenue from Contracts with Customers (Topic 606) See discussion of the ASUs below. January 1, 2018. Earlier application is permitted only as of January 1, 2017. We will adopt the standard on January 1, 2018; see below for the evaluation of the impact of its adoption on the consolidated financial statements.
THE DAYTON POWER AND LIGHT COMPANY [Member]
Related Party Transaction [Line Items]
Schedule of New Accounting Pronouncements	The following table provides a brief description of recent accounting pronouncements that could have a material impact on our financial statements: Accounting Standard Description Date of Adoption Effect on the financial statements upon adoption New Accounting Standards Adopted 2016-09, Compensation - Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting The standard simplifies the following aspects of accounting for share-based payments awards: accounting for income taxes, classification of excess tax benefits on the statement of cash flows, forfeitures, statutory tax withholding requirements, classification of awards as either equity or liabilities and classification of employee taxes paid on statement of cash flows when an employer withholds shares for tax-withholding purposes. Transition method: The recognition of excess tax benefits and tax deficiencies arising from vesting or settlement were applied retrospectively. The elimination of the requirement that excess tax benefits be realized before they are recognized was adopted on a modified retrospective basis with a cumulative adjustment to the opening balance sheet. January 1, 2017 The primary effect of adoption was the recognition of excess tax benefits in our provision for income taxes in the period when the awards vest or are settled, rather than in paid-in-capital in the period when the excess tax benefits are realized. We will continue to estimate the number of awards that are expected to vest in our determination of the related periodic compensation cost. The adoption of this standard did not have a material impact on the financial statements. New Accounting Standards Issued But Not Yet Effective 2017-08, Receivables - Nonrefundable Fees and Other Costs (Subtopic 310-20): Premium Amortization on Purchased Callable Debt Securities This standard shortens the period of amortization of the premium on certain callable debt securities to the earliest call date. January 1, 2019. We are currently evaluating the impact of adopting the standard on our financial statements. 2017-07, Compensation—Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost The standard provides guidance on the presentation of net benefit cost in an employer’s income statement and on the components eligible for capitalization. It requires that an employer report the service cost component in the same line item(s) as other employee compensation costs arising from services rendered during the period, and report the other components of net benefit cost separately from the service cost component and outside a subtotal of operating income. Only the service cost component will be eligible for capitalization. January 1, 2018. Early adoption is permitted. We are currently evaluating the impact of adopting the standard on our financial statements. 2017-01, Business Combinations (Topic 805): Clarifying the Definition of a Business This standard provides guidance to assist the entities with evaluating when a set of transferred assets and activities is a business. January 1, 2018. Early adoption is permitted We are currently evaluating the impact of adopting the standard on our financial statements. Accounting Standard Description Date of Adoption Effect on the financial statements upon adoption 2016-18, Statement of Cash Flows (Topic 320): Restricted Cash (a consensus of the FASB Emerging Issues Task Force) This standard requires that a statement of cash flows explain the change during the period in the total of cash, cash equivalents, and amounts generally described as restricted cash or restricted cash equivalents. Therefore, amounts generally described as restricted cash and restricted cash equivalents should be included with cash and cash equivalents when reconciling the beginning-of-period and end-of-period total amounts shown on the statement of cash flows. January 1, 2018. Early adoption is permitted We are currently evaluating the impact of adopting the standard on our financial statements. 2016-16, Income Taxes (Topic 740): Intra-Entity Transfers of Assets Other Than Inventory This standard requires that an entity recognizes the income tax consequences of an intra-entity transfer of an asset other than inventory when the transfer occurs. January 1, 2018. Early adoption is permitted. We are currently evaluating the impact of adopting the standard on our financial statements. 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Receipts and Cash Payments (a consensus of the Emerging Issues Task Force) This standard provides specific guidance on how certain cash transactions are presented and classified in the statement of cash flows. January 1, 2018. Early adoption is permitted. We are currently evaluating the impact of adopting the standard on our financial statements but do not anticipate a material impact. 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments This standard updates the impairment model for financial assets measured at amortized cost to an expected loss model rather than an incurred loss model. It also allows for the presentation of credit losses on available-for-sale debt securities as an allowance rather than a write down. January 1, 2020. Early adoption is permitted only as of January 1, 2019. We are currently evaluating the impact of adopting the standard on our financial statements. 2016-02, Leases (Topic 842) The standard creates Topic 842, Leases which supersedes Topic 840, Leases, and introduces a lessee model that brings substantially all leases onto the balance sheet while retaining most of the principles of the existing lessor model in U.S. GAAP and aligning many of those principles with ASC 606, Revenue from Contracts with Customers. January 1, 2019. Early adoption is permitted. We are currently evaluating the impact of adopting the standard on our financial statements. 2014-09, 2015-14, 2016-08, 2016-10, 2016-12, 2016-20, 2017-05 Revenue from Contracts with Customers (Topic 606) See discussion of the ASUs below. January 1, 2018. Earlier application is permitted only as of January 1, 2017. We will adopt the standard on January 1, 2018; see below for the evaluation of the impact of its adoption on the financial statements.

Supplemental Financial Inform25

Supplemental Financial Information (Tables)	3 Months Ended
	Mar. 31, 2017
Supplemental Financial Information [Line Items]
Schedule of Supplemental Financial Information	Accounts receivable and Inventories are as follows at March 31, 2017 and December 31, 2016 : March 31, December 31, $ in millions 2017 2016 Accounts receivable, net: Unbilled revenue $ 14.7 $ 43.0 Customer receivables 68.4 73.9 Amounts due from partners in jointly owned plants 6.6 12.7 Other 12.7 6.7 Provision for uncollectible accounts (1.0 ) (1.2 ) Total accounts receivable, net $ 101.4 $ 135.1 Inventories, at average cost: Fuel and limestone $ 38.8 $ 38.9 Plant materials and supplies 20.6 36.6 Other 1.5 1.7 Total inventories, at average cost $ 60.9 $ 77.2
Reclassification out of Accumulated Other Comprehensive Income	The amounts reclassified out of Accumulated Other Comprehensive Income / (Loss) by component during the three months ended March 31, 2017 and 2016 are as follows: Details about Accumulated Other Comprehensive Income / (Loss) components Affected line item in the Condensed Consolidated Statements of Operations Three months ended March 31, $ in millions 2017 2016 Gains and losses on Available-for-sale securities activity (Note 5): Other income $ (0.1 ) $ (0.1 ) Gains and losses on cash flow hedges (Note 6): Interest expense (0.3 ) (0.2 ) Revenue (1.5 ) (17.2 ) Purchased power 3.3 4.4 Total before income taxes 1.5 (13.0 ) Tax expense / (benefit) (0.5 ) 4.8 Net of income taxes 1.0 (8.2 ) Amortization of defined benefit pension items (Note 9): Operation and maintenance 1.3 0.1 Tax benefit (0.5 ) (0.1 ) Net of income taxes 0.8 — Total reclassifications for the period, net of income taxes $ 1.7 $ (8.3 )
Schedule of Accumulated Other Comprehensive Income (Loss)	The changes in the components of Accumulated Other Comprehensive Income / (Loss) during the three months ended March 31, 2017 are as follows: $ in millions Gains / (losses) on available-for-sale securities Gains / (losses) on cash flow hedges Change in unfunded pension obligation Total Balance January 1, 2017 $ 0.6 $ 13.1 $ (13.4 ) $ 0.3 Other comprehensive income / (loss) before reclassifications 0.2 5.2 (1.5 ) 3.9 Amounts reclassified from accumulated other comprehensive income / (loss) (0.1 ) 1.0 0.8 1.7 Net current period other comprehensive income / (loss) 0.1 6.2 (0.7 ) 5.6 Balance March 31, 2017 $ 0.7 $ 19.3 $ (14.1 ) $ 5.9
THE DAYTON POWER AND LIGHT COMPANY [Member]
Supplemental Financial Information [Line Items]
Schedule of Supplemental Financial Information	Accounts receivable and Inventories are as follows at March 31, 2017 and December 31, 2016 : March 31, December 31, $ in millions 2017 2016 Accounts receivable, net: Unbilled revenue $ 14.7 $ 43.0 Customer receivables 65.2 71.2 Amounts due from partners in jointly owned plants 6.6 12.7 Amounts due from affiliates 14.8 2.9 Other 10.3 6.0 Provision for uncollectible accounts (1.0 ) (1.2 ) Total accounts receivable, net $ 110.6 $ 134.6 Inventories, at average cost: Fuel and limestone $ 38.8 $ 38.8 Plant materials and supplies 19.2 35.3 Other 1.5 1.7 Total inventories, at average cost $ 59.5 $ 75.8
Reclassification out of Accumulated Other Comprehensive Income	The amounts reclassified out of Accumulated Other Comprehensive Income / (Loss) by component during the three months ended March 31, 2017 and 2016 are as follows: Details about Accumulated Other Comprehensive Income / (Loss) components Affected line item in the Condensed Statements of Operations Three months ended March 31, $ in millions 2017 2016 Gains and losses on Available-for-sale securities activity (Note 5): Other income $ (0.1 ) $ (0.1 ) Gains and losses on cash flow hedges (Note 6): Interest expense (0.3 ) (0.3 ) Revenue (1.5 ) (17.1 ) Purchased power 3.3 4.4 Total before income taxes 1.5 (13.0 ) Tax expense / (benefit) (0.5 ) 4.6 Net of income taxes 1.0 (8.4 ) Amortization of defined benefit pension items (Note 9): Operation and maintenance 3.8 1.1 Tax benefit (1.3 ) (0.8 ) Net of income taxes 2.5 0.3 Total reclassifications for the period, net of income taxes $ 3.4 $ (8.2 )
Schedule of Accumulated Other Comprehensive Income (Loss)	The changes in the components of Accumulated Other Comprehensive Income / (Loss) during the three months ended March 31, 2017 are as follows: $ in millions Gains / (losses) on available-for-sale securities Gains / (losses) on cash flow hedges Change in unfunded pension obligation Total Balance January 1, 2017 $ 0.7 $ (2.7 ) $ (40.5 ) $ (42.5 ) Other comprehensive income / (loss) before reclassifications 0.2 5.2 (1.6 ) 3.8 Amounts reclassified from accumulated other comprehensive income / (loss) (0.1 ) 1.0 2.5 3.4 Net current period other comprehensive income 0.1 6.2 0.9 7.2 Balance March 31, 2017 $ 0.8 $ 3.5 $ (39.6 ) $ (35.3 )

Property, Plant and Equipment26

Property, Plant and Equipment (Tables)	3 Months Ended
	Mar. 31, 2017
Property, Plant and Equipment [Line Items]
Schedule of Jointly Owned Utility Plants [Table Text Block]	DP&L’s undivided ownership interest in such facilities at March 31, 2017 , is as follows: DP&L Share DPL Carrying Value Ownership (%) Summer Production Capacity (MW) Gross Plant In Service ($ in millions) Accumulated Depreciation ($ in millions) Construction Work in Process ($ in millions) Jointly-owned production units Conesville - Unit 4 16.5 129 $ — $ — $ — Killen - Unit 2 67.0 402 7.0 1.0 1.0 Miami Fort - Units 7 and 8 36.0 368 28.0 1.0 5.0 Stuart - Units 1 through 4 35.0 808 1.0 1.0 — Zimmer - Unit 1 28.1 371 12.0 1.0 5.0 Transmission (at varying percentages) 43.0 11.0 — Total 2,078 $ 91.0 $ 15.0 $ 11.0
Schedule of Change in Asset Retirement Obligation [Table Text Block]	Changes in the Liability for Generation AROs $ in millions Balance January 1, 2017 $ 138.8 Revisions to cash flow and timing estimates (4.4 ) Accretion expense 1.1 Settlements 0.1 Balance March 31, 2017 $ 135.6
Subsidiaries [Member]
Property, Plant and Equipment [Line Items]
Schedule of Jointly Owned Utility Plants [Table Text Block]	DP&L’s undivided ownership interest in such facilities at March 31, 2017 , is as follows: DP&L Share DP&L Carrying Value Ownership % Summer Production Capacity (MW) Gross Plant In Service ($ in millions) Accumulated Depreciation ($ in millions) Construction Work in Process ($ in millions) Jointly-owned production units Conesville - Unit 4 16.5 129 $ — $ — $ — Killen - Unit 2 67.0 402 7.0 1.0 1.0 Miami Fort - Units 7 and 8 36.0 368 28.0 1.0 5.0 Stuart - Units 1 through 4 35.0 808 1.0 1.0 — Zimmer - Unit 1 28.1 371 12.0 1.0 5.0 Transmission (at varying percentages) 99.0 67.0 — Total 2,078 $ 147.0 $ 71.0 $ 11.0
Schedule of Change in Asset Retirement Obligation [Table Text Block]	Changes in the Liability for Generation AROs $ in millions Balance January 1, 2017 $ 135.2 Revisions to cash flow and timing estimates (4.4 ) Accretion expense 1.4 Settlements 0.1 Balance March 31, 2017 $ 132.3

Fair Value (Tables)

Fair Value (Tables)	3 Months Ended
	Mar. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value and Cost Of Non-Derivative Instruments	The following table presents the fair value, carrying value and cost of our non-derivative instruments at March 31, 2017 and December 31, 2016 . Information about the fair value of our derivative instruments can be found in Note 6 – Derivative Instruments and Hedging Activities . March 31, 2017 December 31, 2016 $ in millions Cost Fair Value Cost Fair Value Assets Money market funds $ 0.3 $ 0.3 $ 0.4 $ 0.4 Equity securities 2.6 3.9 2.4 3.4 Debt securities 4.3 4.3 4.4 4.4 Hedge funds 0.1 0.1 — 0.1 Real estate — — 0.3 0.3 Tangible assets 0.1 0.1 0.1 0.1 Total Assets $ 7.4 $ 8.7 $ 7.6 $ 8.7 Carrying Value Fair Value Carrying Value Fair Value Liabilities Debt (a) $ 1,851.6 $ 1,940.7 $ 1,858.0 $ 1,907.7
Fair Value of Assets and Liabilities Measured on Recurring Basis	The fair value of assets and liabilities at March 31, 2017 and December 31, 2016 and the respective category within the fair value hierarchy for DPL was determined as follows: Assets and Liabilities at Fair Value Level 1 Level 2 Level 3 $ in millions Fair value at March 31, 2017 Based on Quoted Prices in Active Markets Other Observable Inputs Unobservable Inputs Assets Master Trust assets Money market funds $ 0.3 $ 0.3 $ — $ — Equity securities 3.9 — 3.9 — Debt securities 4.3 — 4.3 — Hedge funds 0.1 — 0.1 — Tangible assets 0.1 — 0.1 — Total Master Trust assets 8.7 0.3 8.4 — Derivative Assets Forward power contracts 18.9 — 18.9 — Interest rate hedges 1.4 — 1.4 — Natural gas 0.3 0.3 — — Total Derivative assets 20.6 0.3 20.3 — Total Assets $ 29.3 $ 0.6 $ 28.7 $ — Liabilities Derivative Liabilities Interest rate hedges $ 0.3 $ — $ 0.3 $ — Natural gas futures 0.5 0.5 — — Forward power contracts 18.1 — 17.0 1.1 Total Derivative liabilities 18.9 0.5 17.3 1.1 Debt 1,940.6 — 1,922.7 17.9 Total Liabilities $ 1,959.5 $ 0.5 $ 1,940.0 $ 19.0 Assets and Liabilities at Fair Value Level 1 Level 2 Level 3 $ in millions Fair value at December 31, 2016 Based on Quoted Prices in Active Markets Other Observable Inputs Unobservable Inputs Assets Master Trust assets Money market funds $ 0.4 $ 0.4 $ — $ — Equity securities 3.4 — 3.4 — Debt securities 4.4 — 4.4 — Hedge funds 0.1 — 0.1 — Real estate 0.3 — 0.3 — Tangible assets 0.1 — 0.1 — Total Master Trust assets 8.7 0.4 8.3 — Derivative assets Forward power contracts 19.5 — 19.5 — Interest rate hedges 1.2 — 1.2 — FTRs 0.1 — — 0.1 Total Derivative assets 20.8 — 20.7 0.1 Total Assets $ 29.5 $ 0.4 $ 29.0 $ 0.1 Liabilities Derivative liabilities Interest rate hedges $ 0.7 $ — $ 0.7 $ — Forward power contracts 28.5 — 26.0 2.5 Total Derivative liabilities 29.2 — 26.7 2.5 Debt 1,907.7 — 1,889.7 18.0 Total Liabilities $ 1,936.9 $ — $ 1,916.4 $ 20.5
Fair Value Measurements, Nonrecurring [Table Text Block]	When evaluating impairment of long-lived assets, we measure fair value using the applicable fair value measurement guidance. Impairment expense is measured by comparing the fair value at the evaluation date to the carrying amount. The following table summarizes Long-lived assets measured at fair value on a non-recurring basis during the period and their level within the fair value hierarchy (there were no impairments during the three months ended March 31, 2016): $ in millions Three months ended March 31, 2017 Carrying Fair Value Gross Amount (b) Level 1 Level 2 Level 3 Loss Assets Long-lived assets (a) Stuart $ 42.4 $ — $ — $ 3.3 $ 39.1 Killen $ 35.2 $ — $ — $ 7.9 $ 27.3 (a) See Note 14 – Fixed-asset Impairment for further information (b) Carrying amount at date of valuation
Fair Value Inputs, Assets, Quantitative Information [Table Text Block]	The following summarizes the significant unobservable inputs used in the Level 3 measurement on a non-recurring basis during the three months ended March 31, 2017: $ in millions Fair value Valuation technique Unobservable input Weighted average Long-lived assets held and used: Stuart $ 3.3 Discounted cash flow Pre-tax operating margin 10% Weighted-average cost of capital 7% Killen $ 7.9 Discounted cash flow Pre-tax operating margin 22% Weighted-average cost of capital 7%
THE DAYTON POWER AND LIGHT COMPANY [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value and Cost Of Non-Derivative Instruments	The following table presents the fair value, carrying value and cost of our non-derivative instruments at March 31, 2017 and December 31, 2016 . Information about the fair value of our derivative instruments can be found in Note 6 – Derivative Instruments and Hedging Activities . March 31, 2017 December 31, 2016 $ in millions Cost Fair Value Cost Fair Value Assets Money market funds $ 0.3 $ 0.3 $ 0.4 $ 0.4 Equity securities 2.6 3.9 2.4 3.4 Debt securities 4.3 4.3 4.4 4.4 Hedge funds 0.1 0.1 — 0.1 Real estate — — 0.3 0.3 Tangible assets 0.1 0.1 0.1 0.1 Total assets $ 7.4 $ 8.7 $ 7.6 $ 8.7 Carrying Value Fair Value Carrying Value Fair Value Liabilities Debt (a) $ 748.3 $ 762.3 $ 749.0 $ 763.5
Fair Value of Assets and Liabilities Measured on Recurring Basis	The fair value of assets and liabilities at March 31, 2017 and December 31, 2016 and the respective category within the fair value hierarchy for DP&L was determined as follows: Assets and Liabilities at Fair Value Level 1 Level 2 Level 3 $ in millions Fair value at March 31, 2017 Based on Quoted Prices in Active Markets Other Observable Inputs Unobservable Inputs Assets Master Trust assets Money market funds $ 0.3 $ 0.3 $ — $ — Equity securities 3.9 — 3.9 — Debt securities 4.3 — 4.3 — Hedge funds 0.1 — 0.1 — Tangible assets 0.1 — 0.1 — Total Master Trust assets 8.7 0.3 8.4 — Derivative assets Natural gas futures 0.3 0.3 — — Interest rate hedges 1.4 — 1.4 — Forward power contracts 19.0 — 19.0 — Total derivative assets 20.7 0.3 20.4 — Total assets $ 29.4 $ 0.6 $ 28.8 $ — Liabilities Derivative liabilities Interest rate hedges $ 0.3 $ — $ 0.3 $ — Natural gas futures 0.5 0.5 — — Forward power contracts 18.1 — 17.0 1.1 Total derivative liabilities 18.9 0.5 17.3 1.1 Debt 762.3 — 744.4 17.9 Total liabilities $ 781.2 $ 0.5 $ 761.7 $ 19.0 Assets and Liabilities at Fair Value Level 1 Level 2 Level 3 $ in millions Fair value at December 31, 2016 Based on Quoted Prices in Active Markets Other Observable Inputs Unobservable Inputs Assets Master Trust assets Money market funds $ 0.4 $ 0.4 $ — $ — Equity securities 3.4 — 3.4 — Debt securities 4.4 — 4.4 — Hedge funds 0.1 — 0.1 — Real estate 0.3 — 0.3 — Tangible assets 0.1 0.1 — Total Master Trust assets 8.7 0.4 8.3 — Derivative assets FTRs 0.1 — — 0.1 Interest rate hedges 1.2 — 1.2 — Forward power contracts 19.5 — 19.5 — Total Derivative assets 20.8 — 20.7 0.1 Total assets $ 29.5 $ 0.4 $ 29.0 $ 0.1 Liabilities Derivative liabilities Interest rate hedges $ 0.7 $ — $ 0.7 $ — Forward power contracts 28.5 — 26.0 2.5 Total Derivative liabilities 29.2 — 26.7 2.5 Debt 763.5 — 745.5 18.0 Total liabilities $ 792.7 $ — $ 772.2 $ 20.5
Fair Value Measurements, Nonrecurring [Table Text Block]	When evaluating impairment of long-lived assets, we measure fair value using the applicable fair value measurement guidance. Impairment expense is measured by comparing the fair value at the evaluation date to the carrying amount. The following table summarizes Long-lived assets measured at fair value on a non-recurring basis during the period and their level within the fair value hierarchy (there were no impairments during the three months ended March 31, 2016): $ in millions Three months ended March 31, 2017 Carrying Fair Value Gross Amount (b) Level 1 Level 2 Level 3 Loss Assets Long-lived assets (a) Stuart $ 42.3 $ — $ — $ 3.3 $ 39.0 Killen $ 35.2 $ — $ — $ 7.9 $ 27.3 (a) See Note 14 – Fixed-asset Impairment for further information (b) Carrying amount at date of valuation
Fair Value Inputs, Assets, Quantitative Information [Table Text Block]	The following summarizes the significant unobservable inputs used in the Level 3 measurement on a non-recurring basis during the three months ended March 31, 2017: $ in millions Fair value Valuation technique Unobservable input Weighted average Long-lived assets held and used: Stuart $ 3.3 Discounted cash flow Pre-tax operating margin 10 % Weighted-average cost of capital 7% Killen $ 7.9 Discounted cash flow Pre-tax operating margin 22 % Weighted-average cost of capital 7%

Derivative Instruments and He28

Derivative Instruments and Hedging Activities (Tables)	3 Months Ended
	Mar. 31, 2017
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Schedule of Notional Amounts of Outstanding Derivative Positions	At March 31, 2017 , DPL had the following outstanding derivative instruments: Commodity Accounting Treatment (a) Unit Purchases (in thousands) Sales (in thousands) Net Purchases/ (Sales) (in thousands) FTRs Not designated MWh 0.9 — 0.9 Natural gas futures Not designated Dths 17,127.5 — 17,127.5 Forward power contracts Designated MWh 1,276.6 (6,250.9 ) (4,974.3 ) Forward power contracts Not designated MWh 1,727.3 (2,052.6 ) (325.3 ) Interest rate swaps Designated USD $ 200,000.0 $ — $ 200,000.0 (a) Refers to whether the derivative instruments have been designated as a cash flow hedge. At December 31, 2016 , DPL had the following outstanding derivative instruments: Commodity Accounting Treatment (a) Unit Purchases (in thousands) Sales (in thousands) Net Purchases/ (Sales) (in thousands) FTRs Not designated MWh 2.3 — 2.3 Natural gas futures Not designated Dths 1,590.0 — 1,590.0 Forward power contracts Designated MWh 342.9 (9,974.5 ) (9,631.6 ) Forward power contracts Not designated MWh 2,568.3 (2,020.9 ) 547.4 Interest rate swaps Designated USD $ 200,000.0 $ — $ 200,000.0
Gains or Losses Recognized in AOCI for the Cash Flow Hedges	The following table provides information for DPL concerning gains or losses recognized in AOCI for the cash flow hedges for the three months ended March 31, 2017 and 2016 : Three months ended Three months ended March 31, 2017 March 31, 2016 Interest Interest $ in millions (net of tax) Power Rate Hedge Power Rate Hedge Beginning accumulated derivative gains / (losses) in AOCI $ (4.3 ) $ 17.4 $ 9.2 $ 17.5 Net gains associated with current period hedging transactions 4.9 0.3 21.5 — Net gains / (losses) reclassified to earnings Interest expense — (0.2 ) — — Revenues (0.9 ) — (11.0 ) — Purchased power 2.1 — 2.8 — Ending accumulated derivative gains in AOCI $ 1.8 $ 17.5 $ 22.5 $ 17.5 Portion expected to be reclassified to earnings in the next twelve months (a) $ 2.0 $ (0.2 ) Maximum length of time that we are hedging our exposure to variability in future cash flows related to forecasted transactions (in months) 17 41 (a) The actual amounts that we reclassify from AOCI to earnings related to power can differ from the estimate above due to market price changes.
Schedule of Other Derivatives Not Designated as Hedging Instruments, Statements of Financial Performance and Financial Position, Location	The following tables present the amount and classification within the Condensed Consolidated Statements of Operations of the gains and losses on DPL’s derivatives not designated as hedging instruments for the three months ended March 31, 2017 and 2016 : For the three months ended March 31, 2017 $ in millions FTRs Power Natural Gas Total Change in unrealized loss $ — $ (0.1 ) $ (0.1 ) $ (0.2 ) Realized gain / (loss) 0.2 (2.6 ) (0.2 ) (2.6 ) Total $ 0.2 $ (2.7 ) $ (0.3 ) $ (2.8 ) Recorded in Income Statement: gain / (loss) Revenues $ — $ (6.7 ) $ — $ (6.7 ) Purchased power 0.2 4.0 (0.3 ) 3.9 Total $ 0.2 $ (2.7 ) $ (0.3 ) $ (2.8 ) For the three months ended March 31, 2016 $ in millions FTRs Power Natural Gas Total Change in unrealized gain / (loss) $ 0.1 $ (1.5 ) $ (0.2 ) $ (1.6 ) Realized gain / (loss) 0.2 (0.4 ) (0.2 ) (0.4 ) Total $ 0.3 $ (1.9 ) $ (0.4 ) $ (2.0 ) Recorded in Income Statement: gain / (loss) Revenue $ — $ (1.1 ) $ — $ (1.1 ) Purchased power 0.3 (0.8 ) (0.4 ) (0.9 ) Total $ 0.3 $ (1.9 ) $ (0.4 ) $ (2.0 )
Schedule of Derivative Instruments in Statement of Financial Position, Fair Value	The following tables summarize the derivative positions presented in the balance sheet where a right of offset exists under these arrangements and related cash collateral received or pledged. The following table presents the fair value and balance sheet classification of DPL’s derivative instruments at March 31, 2017 : Fair Values of Derivative Instruments at March 31, 2017 Gross Amounts Not Offset in the Condensed Consolidated Balance Sheets $ in millions Hedging Designation Gross Fair Value as presented in the Condensed Consolidated Balance Sheets Financial Instruments with Same Counterparty in Offsetting Position Cash Collateral Net Balance Fair Value Assets Short-term derivative positions (presented in Other prepayments and current assets) Forward power contracts Designated $ 12.7 $ (8.6 ) $ — $ 4.1 Forward power contracts Not designated 6.1 (5.5 ) — 0.6 Natural gas futures Not designated 0.3 (0.2 ) — 0.1 Long-term derivative positions (presented in Other deferred assets) Interest rate swap Designated 1.4 — — 1.4 Forward power contracts Not designated 0.1 (0.1 ) — — Total assets $ 20.6 $ (14.4 ) $ — $ 6.2 Liabilities Short-term derivative positions (presented in Other current liabilities) Forward power contracts Designated $ 9.7 $ (8.6 ) $ — $ 1.1 Interest rate swap Designated 0.3 — — 0.3 Forward power contracts Not designated 8.1 (5.5 ) (0.1 ) 2.5 Natural gas futures Not designated 0.2 (0.2 ) — — Long-term derivative positions (presented in Other deferred credits) Forward power contracts Designated 0.1 — (0.1 ) — Natural gas futures Not designated 0.3 — (0.3 ) — Forward power contracts Not designated 0.2 (0.1 ) — 0.1 Total liabilities $ 18.9 $ (14.4 ) $ (0.5 ) $ 4.0 The following table presents the fair value and balance sheet classification of DPL’s derivative instruments at December 31, 2016 : Fair Values of Derivative Instruments at December 31, 2016 Gross Amounts Not Offset in the Condensed Consolidated Balance Sheets $ in millions Hedging Designation Gross Fair Value as presented in the Condensed Consolidated Balance Sheets Financial Instruments with Same Counterparty in Offsetting Position Cash Collateral Net Balance Fair Value Assets Short-term derivative positions (presented in Other prepayments and current assets) Forward power contracts Designated $ 11.0 $ (10.5 ) $ — $ 0.5 Forward power contracts Not designated 6.0 (4.7 ) — 1.3 FTRs Not designated 0.1 — — 0.1 Long-term derivative positions (presented in Other deferred assets) Interest rate swaps Designated 1.2 — — 1.2 Forward power contracts Designated 0.6 (0.6 ) — — Forward power contracts Not designated 1.9 (1.0 ) — 0.9 Total assets $ 20.8 $ (16.8 ) $ — $ 4.0 Liabilities Short-term derivative positions (presented in Other current liabilities) Interest rate swaps Designated $ 0.7 $ — $ — $ 0.7 Forward power contracts Designated 16.4 (10.5 ) (5.5 ) 0.4 Forward power contracts Not designated 7.7 (4.7 ) — 3.0 Long-term derivative positions (presented in Other deferred credits) Forward power contracts Designated 2.4 (0.6 ) (0.8 ) 1.0 Forward power contracts Not designated 2.0 (1.0 ) — 1.0 Total liabilities $ 29.2 $ (16.8 ) $ (6.3 ) $ 6.1
THE DAYTON POWER AND LIGHT COMPANY [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Schedule of Notional Amounts of Outstanding Derivative Positions	At March 31, 2017 , DP&L had the following outstanding derivative instruments: Commodity Accounting Treatment (a) Unit Purchases (in thousands) Sales (in thousands) Net Purchases/ (Sales) (in thousands) FTRs Not designated MWh 0.9 — 0.9 Natural gas futures Not designated Dths 17,127.5 — 17,127.5 Forward power contracts Designated MWh 1,276.6 (6,250.9 ) (4,974.3 ) Forward power contracts Not designated MWh 1,727.3 (2,057.9 ) (330.6 ) Interest rate swaps Designated USD $ 200,000.0 $ — $ 200,000.0 (a) Refers to whether the derivative instruments have been designated as a cash flow hedge. At December 31, 2016 , DP&L had the following outstanding derivative instruments: Commodity Accounting Treatment (a) Unit Purchases (in thousands) Sales (in thousands) Net Purchases/ (Sales) (in thousands) FTRs Not designated MWh 2.3 — 2.3 Natural gas futures Not designated Dths 1,590.0 — 1,590.0 Forward power contracts Designated MWh 342.9 (9,974.5 ) (9,631.6 ) Forward power contracts Not designated MWh 2,568.3 (2,037.5 ) 530.8 Interest rate swaps Designated USD $ 200,000.0 $ — $ 200,000.0
Gains or Losses Recognized in AOCI for the Cash Flow Hedges	The following table provides information for DP&L concerning gains or losses recognized in AOCI for the cash flow hedges for the three months ended March 31, 2017 and 2016 : Three months ended Three months ended March 31, 2017 March 31, 2016 Interest Interest $ in millions (net of tax) Power Rate Hedge Power Rate Hedge Beginning accumulated derivative gains / (losses) in AOCI $ (4.3 ) $ 1.6 $ 9.2 $ 2.0 Net gains associated with current period hedging transactions 4.9 0.3 21.5 — Net gains / (losses) reclassified to earnings Interest expense — (0.2 ) — (0.2 ) Revenues (0.9 ) — (11.0 ) — Purchased power 2.1 — 2.8 — Ending accumulated derivative gains in AOCI $ 1.8 $ 1.7 $ 22.5 $ 1.8 Portion expected to be reclassified to earnings in the next twelve months (a) $ 2.0 $ (0.2 ) Maximum length of time that we are hedging our exposure to variability in future cash flows related to forecasted transactions (in months) 17 41 (a) The actual amounts that we reclassify from AOCI to earnings related to power can differ from the estimate above due to market price changes.
Schedule of Other Derivatives Not Designated as Hedging Instruments, Statements of Financial Performance and Financial Position, Location	The following tables present the amount and classification within the Condensed Statements of Operations of the gains and losses on DP&L's derivatives not designated as hedging instruments for the three months ended March 31, 2017 and 2016 : For the three months ended March 31, 2017 $ in millions FTRs Power Natural Gas Total Change in unrealized loss $ — $ (0.1 ) $ (0.1 ) $ (0.2 ) Realized gain / (loss) 0.2 (2.6 ) (0.2 ) (2.6 ) Total $ 0.2 $ (2.7 ) $ (0.3 ) $ (2.8 ) Recorded in Income Statement: gain / (loss) Revenues $ — $ (6.7 ) $ — $ (6.7 ) Purchased power 0.2 4.0 (0.3 ) 3.9 Total $ 0.2 $ (2.7 ) $ (0.3 ) $ (2.8 ) For the three months ended March 31, 2016 $ in millions FTRs Power Natural Gas Total Change in unrealized gain / (loss) $ 0.1 $ (1.9 ) (0.2 ) $ (2.0 ) Realized gain / (loss) 0.2 (0.3 ) (0.2 ) (0.3 ) Total $ 0.3 $ (2.2 ) $ (0.4 ) $ (2.3 ) Recorded in Income Statement: gain / (loss) Revenues — (1.4 ) — (1.4 ) Purchased power 0.3 (0.8 ) (0.4 ) (0.9 ) Total $ 0.3 $ (2.2 ) $ (0.4 ) $ (2.3 )
Schedule of Derivative Instruments in Statement of Financial Position, Fair Value	DP&L’s derivative instruments at March 31, 2017 : Fair Values of Derivative Instruments at March 31, 2017 Gross Amounts Not Offset in the Condensed Balance Sheets $ in millions Hedging Designation Gross Fair Value as presented in the Condensed Balance Sheets Financial Instruments with Same Counterparty in Offsetting Position Cash Collateral Net Balance Fair Value Assets Short-term derivative positions (presented in Other prepayments and current assets) Forward power contracts Designated $ 12.7 $ (8.6 ) $ — $ 4.1 Forward power contracts Not designated 6.2 (5.5 ) — 0.7 Natural gas futures Not designated 0.3 (0.2 ) — 0.1 Long-term derivative positions (presented in Other deferred assets) Interest rate swaps Designated 1.4 — — 1.4 Forward power contracts Not designated 0.1 (0.1 ) — — Total assets $ 20.7 $ (14.4 ) $ — $ 6.3 Liabilities Short-term derivative positions (presented in Other current liabilities) Forward power contracts Designated $ 9.7 $ (8.6 ) $ — $ 1.1 Interest rate swaps Designated 0.3 — — 0.3 Forward power contracts Not designated 8.1 (5.5 ) (0.1 ) 2.5 Natural gas futures Not designated 0.2 (0.2 ) — — Long-term derivative positions (presented in Other deferred credits) Forward power contracts Designated 0.1 — (0.1 ) — Natural gas futures Not designated 0.3 — (0.3 ) — Forward power contracts Not designated 0.2 (0.1 ) — 0.1 Total liabilities $ 18.9 $ (14.4 ) $ (0.5 ) $ 4.0 The following table presents the fair value and balance sheet classification of DP&L’s derivative instruments at December 31, 2016 : Fair Values of Derivative Instruments at December 31, 2016 Gross Amounts Not Offset in the Condensed Balance Sheets $ in millions Hedging Designation Gross Fair Value as presented in the Condensed Balance Sheets Financial Instruments with Same Counterparty in Offsetting Position Cash Collateral Net Balance Fair Value Assets Short-term derivative positions (presented in Other prepayments and current assets) Forward power contracts Designated $ 11.0 $ (10.5 ) $ — $ 0.5 Forward power contracts Not designated 6.0 (4.7 ) — 1.3 FTRs Not designated 0.1 — — 0.1 Long-term derivative positions (presented in Other deferred assets) Interest rate swaps Designated 1.2 — — 1.2 Forward power contracts Designated 0.6 (0.6 ) — — Forward power contracts Not designated 1.9 (1.0 ) — 0.9 Total assets $ 20.8 $ (16.8 ) $ — $ 4.0 Liabilities Short-term derivative positions (presented in Other current liabilities) Forward power contracts Designated $ 16.4 $ (10.5 ) $ (5.5 ) $ 0.4 Interest rate swaps Designated 0.7 — — 0.7 Forward power contracts Not designated 7.7 (4.7 ) — 3.0 Long-term derivative positions (presented in Other deferred credits) Forward power contracts Designated 2.4 (0.6 ) (0.8 ) 1.0 Forward power contracts Not designated 2.0 (1.0 ) — 1.0 Total liabilities $ 29.2 $ (16.8 ) $ (6.3 ) $ 6.1

Debt (Tables)

Debt (Tables)	3 Months Ended
	Mar. 31, 2017
Debt Instrument [Line Items]
Long-term Debt	Interest March 31, December 31, $ in millions Rate Maturity 2017 2016 Term loan - rates from 4.01% - 4.04% (a) and 4.00% - 4.01% (b) 2022 $ 443.9 $ 445.0 Tax-exempt First Mortgage Bonds 4.8% 2036 100.0 100.0 Tax-exempt First Mortgage Bonds - rates from 1.52% - 1.53% (a) and 1.29% - 1.42% (b) 2020 200.0 200.0 U.S. Government note 4.2% 2061 17.9 18.0 Capital leases 0.4 0.4 Unamortized deferred financing costs (10.1 ) (10.7 ) Unamortized debt discount and premiums, net (5.3 ) (5.5 ) Total long-term debt at consolidated subsidiary 746.8 747.2 Bank term loan - rates from 3.02% - 3.73% (a) and 2.67% - 3.02% (b) 2020 118.8 125.0 Senior unsecured notes 6.75% 2019 200.0 200.0 Senior unsecured notes 7.25% 2021 780.0 780.0 Note to DPL Capital Trust II (c) 8.125% 2031 15.6 15.6 Unamortized deferred financing costs (8.4 ) (8.8 ) Unamortized debt discounts and premiums, net (0.8 ) (0.6 ) Total long-term debt 1,852.0 1,858.4 Less: current portion (29.7 ) (29.7 ) Long-term debt, net of current portion $ 1,822.3 $ 1,828.7
THE DAYTON POWER AND LIGHT COMPANY [Member]
Debt Instrument [Line Items]
Long-term Debt	Interest March 31, December 31, $ in millions Rate Maturity 2017 2016 Term loan - rates from 4.01% - 4.04% (a) and 4.00% - 4.01% (b) 2022 $ 443.9 $ 445.0 Tax-exempt First Mortgage Bonds 4.8% 2036 100.0 100.0 Tax-exempt First Mortgage Bonds - rates from 1.52% - 1.53% (a) and 1.29% - 1.42% (b) 2020 200.0 200.0 U.S. Government note 4.2% 2061 17.9 18.0 Capital leases 0.4 0.4 Unamortized deferred financing costs (11.5 ) (11.8 ) Unamortized debt discount (2.0 ) (2.2 ) Total long-term debt 748.7 749.4 Less: current portion (4.7 ) (4.7 ) Long-term debt, net of current portion $ 744.0 $ 744.7

Income Taxes (Tables)

Income Taxes (Tables)	3 Months Ended
	Mar. 31, 2017
Entity Information [Line Items]
Schedule of Effective Income Tax Rates	The following table details the effective tax rates for the three months ended March 31, 2017 and 2016 . Three months ended March 31, 2017 2016 DPL 37.9% 21.4%
THE DAYTON POWER AND LIGHT COMPANY [Member]
Entity Information [Line Items]
Schedule of Effective Income Tax Rates	The following table details the effective tax rates for the three months ended March 31, 2017 and 2016 . Three months ended March 31, 2017 2016 DP&L 34.4% 26.9%

Benefit Plans (Tables)

Benefit Plans (Tables)	3 Months Ended
	Mar. 31, 2017
Entity Information [Line Items]
Schedule of Net Periodic Benefit Cost / (Income)	The net periodic benefit cost of the pension benefit plans for the three months ended March 31, 2017 and 2016 was: Net Periodic Benefit Cost Pension Three months ended March 31, $ in millions 2017 2016 Service cost $ 1.4 $ 1.4 Interest cost 3.6 3.7 Expected return on plan assets (5.7 ) (5.7 ) Plan curtailment (a) 4.1 — Amortization of unrecognized: Prior service cost 0.4 0.5 Actuarial loss 1.3 1.0 Net periodic benefit cost $ 5.1 $ 0.9 (a) As a result of the decision to retire certain of DP&L's coal-fired plants, we recognized a plan curtailment of $4.1 million in the first quarter of 2017. See Note 14 – Fixed-asset Impairment for more information.
Estimated Future Benefit Payments and Medicare Part D Reimbursements	Benefit payments, which reflect future service, are estimated to be paid as follows: $ in millions Estimated to be paid during the twelve months ending March 31, Pension 2018 $ 18.8 2019 25.5 2020 26.0 2021 26.4 2022 26.7 2023 - 2027 139.6
THE DAYTON POWER AND LIGHT COMPANY [Member]
Entity Information [Line Items]
Schedule of Net Periodic Benefit Cost / (Income)	The net periodic benefit cost of the pension benefit plans for the three months ended March 31, 2017 and 2016 was: Net Periodic Benefit Cost Pension Three months ended March 31, $ in millions 2017 2016 Service cost $ 1.4 $ 1.4 Interest cost 3.6 3.7 Expected return on plan assets (5.7 ) (5.7 ) Plan curtailment (a) 5.6 — Amortization of unrecognized: Prior service cost 0.5 0.8 Actuarial loss 2.2 1.8 Net periodic benefit cost $ 7.6 $ 2.0 (a) As a result of the decision to retire certain of DP&L's coal-fired plants, we recognized a plan curtailment of $5.6 million in the first quarter of 2017. See Note 14 – Fixed-asset Impairment for more information.
Estimated Future Benefit Payments and Medicare Part D Reimbursements	Benefit payments, which reflect future service, are estimated to be paid as follows: $ in millions Estimated to be paid during the twelve months ending March 31, Pension 2018 $ 18.8 2019 25.5 2020 26.0 2021 26.4 2022 26.7 2023 - 2027 139.6

Related Party Transactions (Tab

Related Party Transactions (Tables)	3 Months Ended
	Mar. 31, 2017
Related Party Transaction [Line Items]
Schedule of Related Party Transactions	The following table provides a summary of these transactions: Three months ended March 31, $ in millions 2017 2016 Transactions with the Service Company Charges for services provided $ 13.9 $ 11.6 Charges to the Service Company $ 1.0 $ 1.2 Transactions with other AES affiliates: Charges for health, welfare and benefit plans $ 4.2 $ 4.1 Balances with the Service Company: At March 31, 2017 At December 31, 2016 Net payable to the Service Company $ — $ (2.0 ) Net payable to other AES affiliates $ (3.1 ) $ (2.5 )
THE DAYTON POWER AND LIGHT COMPANY [Member]
Related Party Transaction [Line Items]
Schedule of Related Party Transactions	The following table provides a summary of these transactions: Three months ended March 31, $ in millions 2017 2016 DP&L Operation & Maintenance Expenses: Premiums paid for insurance services provided by MVIC (a) $ (0.8 ) $ (0.9 ) Transactions with the Service Company: Charges for services provided $ 13.0 $ 8.9 Charges to the Service Company $ 1.0 $ 1.2 Transactions with other AES affiliates: Charges for health, welfare and benefit plans $ 4.1 $ 4.1 Balances with related parties: At March 31, 2017 At December 31, 2016 Net payable to the Service Company $ — $ (2.0 ) Short-term loan with DPL (b) $ — $ 5.0 Net prepayment with / (payable to) other AES affiliates $ 5.0 $ (2.5 ) (a) MVIC, a wholly-owned captive insurance subsidiary of DPL , provides insurance coverage to DP&L and other DPL subsidiaries for workers’ compensation, general liability, property damages and directors’ and officers’ liability. These amounts represent insurance premiums paid by DP&L to MVIC. DP&L received insurance proceeds from MVIC of $0.0 million and $0.2 million for the three months ended March 31, 2017 and 2016, respectively. (b) On December 31, 2016, DPL loaned $5.0 million to DP&L through an intercompany short-term loan at 3.02% .

Business Segments (Tables)

Business Segments (Tables)	3 Months Ended
	Mar. 31, 2017
Segment Reporting Information [Line Items]
Financial Reporting for Reportable Business Segments	The following tables present financial information for each of DPL’s reportable business segments: $ in millions T&D Generation Other Adjustments and Eliminations DPL Consolidated Three months ended March 31, 2017 Revenues from external customers $ 189.8 $ 131.8 $ 2.3 $ — $ 323.9 Intersegment revenues 0.3 — 1.4 (1.7 ) — Total revenues $ 190.1 $ 131.8 $ 3.7 $ (1.7 ) $ 323.9 Depreciation and amortization $ 18.1 $ 7.0 $ 2.9 $ — $ 28.0 Fixed-asset impairment (Note 14) $ — $ 66.3 $ 0.1 $ — $ 66.4 Interest expense $ 7.4 $ — $ 19.6 $ (0.1 ) $ 26.9 Income / (loss) from continuing operations before income tax $ 25.0 $ (86.8 ) $ (21.4 ) $ — $ (83.2 ) Cash capital expenditures $ 26.3 $ 14.1 $ 1.0 $ — $ 41.4 At March 31, 2017 Total assets $ 1,680.9 $ 366.1 $ 633.6 $ (416.4 ) $ 2,264.2 $ in millions T&D Generation Other Adjustments and Eliminations DPL Consolidated Three months ended March 31, 2016 Revenues from external customers $ 204.2 $ 158.2 $ 1.6 $ — $ 364.0 Intersegment revenues 0.3 — 1.3 (1.6 ) — Total revenues $ 204.5 $ 158.2 $ 2.9 $ (1.6 ) $ 364.0 Depreciation and amortization $ 17.2 $ 18.6 $ (2.4 ) $ — $ 33.4 Interest expense $ 5.4 $ 0.1 $ 20.9 $ (0.1 ) $ 26.3 Income / (loss) from continuing operations before income tax $ 34.2 $ (12.3 ) $ (19.1 ) $ — $ 2.8 Cash capital expenditures $ 24.1 $ 13.0 $ 0.6 $ — $ 37.7 At December 31, 2016 Total assets $ 1,710.5 $ 472.3 $ 673.6 $ (437.2 ) $ 2,419.2
Subsidiaries [Member]
Segment Reporting Information [Line Items]
Financial Reporting for Reportable Business Segments	The following tables present financial information for each of DP&L’s reportable business segments: $ in millions T&D Generation Adjustments and Eliminations DP&L Total Three months ended March 31, 2017 Revenues from external customers $ 190.1 $ 121.0 $ — $ 311.1 Intersegment revenues — — — — Total revenues $ 190.1 $ 121.0 $ — $ 311.1 Depreciation and amortization $ 18.1 $ 5.4 $ — $ 23.5 Fixed-asset impairment (Note 14) $ — $ 66.3 $ — $ 66.3 Interest expense $ 7.4 $ 0.2 $ — $ 7.6 Income / (loss) from operations before income tax $ 25.0 $ (88.7 ) $ — $ (63.7 ) Cash capital expenditures $ 26.3 $ 7.8 $ — $ 34.1 At March 31, 2017 Total assets $ 1,680.9 $ 209.0 $ — $ 1,889.9 $ in millions T&D Generation Adjustments and Eliminations DP&L Total Three months ended March 31, 2016 Revenues from external customers $ 204.5 $ 144.7 $ — $ 349.2 Intersegment revenues — — — — Total revenues $ 204.5 $ 144.7 $ — $ 349.2 Depreciation and amortization $ 17.2 $ 17.1 $ — $ 34.3 Interest expense $ 5.2 $ 0.1 $ — $ 5.3 Income from operations before income tax $ 34.4 $ 11.7 $ — $ 46.1 Cash capital expenditures $ 24.1 $ 11.7 $ — $ 35.8 At December 31, 2016 Total assets $ 1,710.5 $ 324.6 $ — $ 2,035.1

Discontinued Operations (Tables

Discontinued Operations (Tables)	3 Months Ended
	Mar. 31, 2017
Discontinued Operations and Disposal Groups [Abstract]
Summary of Balance Sheet and Profit and Loss Information for Discontinued Operations	The following table summarizes the revenues, cost of revenues, operating expenses and income tax of discontinued operations for the periods indicated: Three months ended $ in millions 2016 Revenues $ — Cost of revenues — Operating expenses (0.7 ) Loss from discontinued operations before income taxes (0.7 ) Gain from disposal of discontinued operations 49.2 Income tax expense 18.9 Income on discontinued operations $ 29.6

Summary of Significant Accoun35

Summary of Significant Accounting Policies (Narrative) (Details) $ in Millions	1 Months Ended	3 Months Ended
	Jan. 31, 2016	Mar. 31, 2017USD ($)mi²employeesegmentgenerating_facilitycustomer	Mar. 31, 2016USD ($)	Dec. 31, 2016USD ($)
Significant Accounting Policies [Line Items]
Number of reportable segments | segment		2
Entity number of employees | employee		1,153
Employees under a collective bargaining agreement which expires in October-2011		62.00%
Excise taxes collected		$ 12.5	$ 12.9
THE DAYTON POWER AND LIGHT COMPANY [Member]
Significant Accounting Policies [Line Items]
Approximate number of retail customers | customer		520,000
Service area, square miles | mi²		6,000
Number of Operating Segments | segment		2
Entity number of employees | employee		1,145
Employees under a collective bargaining agreement which expires in October-2011		62.00%
Number Of Generating Facilities | generating_facility		5
Excise taxes collected		$ 12.5	$ 12.9
Line of Credit [Member]
Significant Accounting Policies [Line Items]
Noncurrent portion of deferred finance costs
Line of Credit [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Significant Accounting Policies [Line Items]
Noncurrent portion of deferred finance costs
Adjustments for New Accounting Pronouncement [Member]
Significant Accounting Policies [Line Items]
Current portion of deferred finance costs
Noncurrent portion of deferred finance costs
Adjustments for New Accounting Pronouncement [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Significant Accounting Policies [Line Items]
Current portion of deferred finance costs
Noncurrent portion of deferred finance costs
Year 2016 [Member]
Significant Accounting Policies [Line Items]
Electric generation through competitive bid	100.00%

Supplemental Financial Inform36

Supplemental Financial Information (Supplemental Financial Information) (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Supplemental Financial Information [Line Items]
Unbilled revenue	$ 14.7	$ 43
Customer receivables	68.4	73.9
Amounts due from partners in jointly owned stations	6.6	12.7
Other	12.7	6.7
Provision for uncollectible accounts	(1)	(1.2)
Total accounts receivable, net	101.4	135.1
Fuel and limestone	38.8	38.9
Plant materials and supplies	20.6	36.6
Other	1.5	1.7
Total inventories, at average cost	60.9	77.2
THE DAYTON POWER AND LIGHT COMPANY [Member]
Supplemental Financial Information [Line Items]
Unbilled revenue	14.7	43
Customer receivables	65.2	71.2
Amounts due from partners in jointly owned stations	6.6	12.7
Amounts due from affiliates	14.8	2.9
Other	10.3	6
Provision for uncollectible accounts	(1)	(1.2)
Total accounts receivable, net	110.6	134.6
Fuel and limestone	38.8	38.8
Plant materials and supplies	19.2	35.3
Other	1.5	1.7
Total inventories, at average cost	$ 59.5	$ 75.8

Supplemental Financial Inform37

Supplemental Financial Information (Reclassification out of ACOI) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Other income	$ (27.9)	$ (29.4)
Tax expense	31.5	(0.6)
Net income / (loss)	(51.7)	31.8
Interest expense	(26.9)	(26.3)
Revenue	323.9	364
Purchased power	(102)	(121.9)
Operating Expenses	(223.1)	(143)
THE DAYTON POWER AND LIGHT COMPANY [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Other income	(8.5)	(5.6)
Tax expense	21.9	(12.4)
Net income / (loss)	(41.8)	33.7
Interest expense	(7.6)	(5.3)
Revenue	311.1	349.2
Purchased power	(100.8)	(121.3)
Operating Expenses	(215.4)	(113.3)
Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Net income / (loss)	1.7	(8.3)
Reclassification out of Accumulated Other Comprehensive Income [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Net income / (loss)	3.4	(8.2)
Gains / (losses) on available-for-sale securities [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Other income	(0.1)	(0.1)
Gains / (losses) on available-for-sale securities [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Other income	(0.1)	(0.1)
Gains / (losses) on cash flow hedges [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Tax expense	(0.5)	4.8
Net income / (loss)	1	(8.2)
Interest expense	(0.3)	(0.2)
Revenue	(1.5)	(17.2)
Purchased power	3.3	4.4
Total before income taxes	1.5	(13)
Gains / (losses) on cash flow hedges [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Tax expense	(0.5)	4.6
Net income / (loss)	1	(8.4)
Interest expense	(0.3)	(0.3)
Revenue	(1.5)	(17.1)
Purchased power	3.3	4.4
Total before income taxes	1.5	(13)
Amortization of defined benefit pension items [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Tax expense	(0.5)	(0.1)
Net income / (loss)	0.8	0
Operating Expenses	1.3	0.1
Amortization of defined benefit pension items [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Tax expense	(1.3)	(0.8)
Net income / (loss)	2.5	0.3
Operating Expenses	$ 3.8	$ 1.1

Supplemental Financial Inform38

Supplemental Financial Information (Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, beginning of period	$ 0.3
Other comprehensive income before reclassifications	3.9
Amounts reclassified from accumulated other comprehensive income / (loss)	1.7
Other comprehensive income / (loss)	5.6	$ 13.4
Balance, end of period	5.9
THE DAYTON POWER AND LIGHT COMPANY [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, beginning of period	(42.5)
Other comprehensive income before reclassifications	3.8
Amounts reclassified from accumulated other comprehensive income / (loss)	3.4
Other comprehensive income / (loss)	7.2	$ 13.5
Balance, end of period	(35.3)
Gains / (losses) on available-for-sale securities [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, beginning of period	0.6
Other comprehensive income before reclassifications	0.2
Amounts reclassified from accumulated other comprehensive income / (loss)	(0.1)
Other comprehensive income / (loss)	0.1
Balance, end of period	0.7
Gains / (losses) on available-for-sale securities [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, beginning of period	0.7
Other comprehensive income before reclassifications	0.2
Amounts reclassified from accumulated other comprehensive income / (loss)	(0.1)
Other comprehensive income / (loss)	0.1
Balance, end of period	0.8
Gains / (losses) on cash flow hedges [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, beginning of period	13.1
Other comprehensive income before reclassifications	5.2
Amounts reclassified from accumulated other comprehensive income / (loss)	1
Other comprehensive income / (loss)	6.2
Balance, end of period	19.3
Gains / (losses) on cash flow hedges [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, beginning of period	(2.7)
Other comprehensive income before reclassifications	5.2
Amounts reclassified from accumulated other comprehensive income / (loss)	1
Other comprehensive income / (loss)	6.2
Balance, end of period	3.5
Change in unfunded pension obligation [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, beginning of period	(13.4)
Other comprehensive income before reclassifications	(1.5)
Amounts reclassified from accumulated other comprehensive income / (loss)	0.8
Other comprehensive income / (loss)	(0.7)
Balance, end of period	(14.1)
Change in unfunded pension obligation [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, beginning of period	(40.5)
Other comprehensive income before reclassifications	(1.6)
Amounts reclassified from accumulated other comprehensive income / (loss)	2.5
Other comprehensive income / (loss)	0.9
Balance, end of period	$ (39.6)

Regulatory Matters (Details)

Regulatory Matters (Details) - USD ($)	Mar. 13, 2017	Oct. 11, 2016	Dec. 31, 2016
Distribution Modernization Rider		$ 145,000,000
Distribution Modernization Rider Period		7 years
Regulatory Assets, Renewable Energy Recovery		$ 10,500,000
Energy Reduction Riders		0
Non-bypassable DMR	$ 105,000,000
Service stability rider per year			$ 110,000,000
Subsidiaries [Member]
Distribution Modernization Rider		$ 145,000,000
Distribution Modernization Rider Period		7 years
Regulatory Assets, Renewable Energy Recovery		$ 10,500,000
Energy Reduction Riders		$ 0
Non-bypassable DMR	$ 105,000,000
Service stability rider per year			$ 110,000,000

Property, Plant and Equipment40

Property, Plant and Equipment (Details) $ in Millions	3 Months Ended
	Mar. 31, 2017USD ($)generating_facilitypower_plantMW	Mar. 31, 2016USD ($)	Apr. 21, 2017USD ($)	Dec. 31, 2016USD ($)
Property, Plant and Equipment [Line Items]
Asset Retirement Obligation	$ 135.6			$ 138.8
Asset Retirement Obligation, Revision of Estimate	(4.4)
Asset Retirement Obligation, Accretion Expense	1.1
Asset Retirement Obligation, Liabilities Settled	0.1
Gain (Loss) on Sale of Assets and Asset Impairment Charges	(19.4)	$ (0.1)
Electric Transmission [Member] | Dpandl Investment [Member]
Property, Plant and Equipment [Line Items]
Jointly Owned Utility Plant, Gross Ownership Amount of Plant in Service	43
Jointly Owned Utility Plant, Ownership Amount of Plant Accumulated Depreciation	11
Total Jointly Owned Stations [Member] | Dpandl Investment [Member]
Property, Plant and Equipment [Line Items]
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress	11
Jointly Owned Utility Plant, Gross Ownership Amount of Plant in Service	91
Jointly Owned Utility Plant, Ownership Amount of Plant Accumulated Depreciation	$ 15
Total Jointly Owned Stations [Member] | Dpandl Share [Member]
Property, Plant and Equipment [Line Items]
Production Plan Capacity | MW	2,078
Conesville Unit Four [Member] | Dpandl Investment [Member]
Property, Plant and Equipment [Line Items]
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress	$ 0
Jointly Owned Utility Plant, Gross Ownership Amount of Plant in Service	0
Jointly Owned Utility Plant, Ownership Amount of Plant Accumulated Depreciation	$ 0
Conesville Unit Four [Member] | Dpandl Share [Member]
Property, Plant and Equipment [Line Items]
Jointly Owned Utility Plant, Proportionate Ownership Share	16.50%
Killen Station [Member] | Dpandl Investment [Member]
Property, Plant and Equipment [Line Items]
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress	$ 1
Jointly Owned Utility Plant, Gross Ownership Amount of Plant in Service	7
Jointly Owned Utility Plant, Ownership Amount of Plant Accumulated Depreciation	$ 1
Killen Station [Member] | Dpandl Share [Member]
Property, Plant and Equipment [Line Items]
Jointly Owned Utility Plant, Proportionate Ownership Share	67.00%
Miami Fort Unit Seven And Eight [Member] | Dpandl Investment [Member]
Property, Plant and Equipment [Line Items]
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress	$ 5
Jointly Owned Utility Plant, Gross Ownership Amount of Plant in Service	28
Jointly Owned Utility Plant, Ownership Amount of Plant Accumulated Depreciation	$ 1
Miami Fort Unit Seven And Eight [Member] | Dpandl Share [Member]
Property, Plant and Equipment [Line Items]
Jointly Owned Utility Plant, Proportionate Ownership Share	36.00%
Stuart Station [Member] | Dpandl Investment [Member]
Property, Plant and Equipment [Line Items]
Write off of net book value	$ 6.4
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress	0
Jointly Owned Utility Plant, Gross Ownership Amount of Plant in Service	1
Jointly Owned Utility Plant, Ownership Amount of Plant Accumulated Depreciation	1
Gain (Loss) on Sale of Assets and Asset Impairment Charges	$ 3.2
Stuart Station [Member] | Dpandl Share [Member]
Property, Plant and Equipment [Line Items]
Jointly Owned Utility Plant, Proportionate Ownership Share	35.00%
Zimmer Station [Member] | Dpandl Investment [Member]
Property, Plant and Equipment [Line Items]
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress	$ 5
Jointly Owned Utility Plant, Gross Ownership Amount of Plant in Service	12
Jointly Owned Utility Plant, Ownership Amount of Plant Accumulated Depreciation	$ 1
Zimmer Station [Member] | Dpandl Share [Member]
Property, Plant and Equipment [Line Items]
Jointly Owned Utility Plant, Proportionate Ownership Share	28.10%
Subsidiaries [Member]
Property, Plant and Equipment [Line Items]
Number Of Coal Fired Power Plants | power_plant	5
Asset Retirement Obligation	$ 132.3			$ 135.2
Asset Retirement Obligation, Revision of Estimate	$ (4.4)
Number Of Generating Facilities | generating_facility	5
Asset Retirement Obligation, Accretion Expense	$ 1.4
Asset Retirement Obligation, Liabilities Settled	0.1
Gain (Loss) on Sale of Assets and Asset Impairment Charges	(19.4)	$ (0.1)
Subsidiaries [Member] | Electric Transmission [Member] | Dpandl Investment [Member]
Property, Plant and Equipment [Line Items]
Jointly Owned Utility Plant, Gross Ownership Amount of Plant in Service	99
Jointly Owned Utility Plant, Ownership Amount of Plant Accumulated Depreciation	67
Subsidiaries [Member] | Total Jointly Owned Stations [Member] | Dpandl Investment [Member]
Property, Plant and Equipment [Line Items]
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress	11
Jointly Owned Utility Plant, Gross Ownership Amount of Plant in Service	147
Jointly Owned Utility Plant, Ownership Amount of Plant Accumulated Depreciation	$ 71
Subsidiaries [Member] | Total Jointly Owned Stations [Member] | Dpandl Share [Member]
Property, Plant and Equipment [Line Items]
Production Plan Capacity | MW	2,078
Subsidiaries [Member] | Conesville Unit Four [Member] | Dpandl Investment [Member]
Property, Plant and Equipment [Line Items]
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress	$ 0
Jointly Owned Utility Plant, Gross Ownership Amount of Plant in Service	0
Jointly Owned Utility Plant, Ownership Amount of Plant Accumulated Depreciation	$ 0
Subsidiaries [Member] | Conesville Unit Four [Member] | Dpandl Share [Member]
Property, Plant and Equipment [Line Items]
Jointly Owned Utility Plant, Proportionate Ownership Share	16.50%
Production Plan Capacity | MW	129
Subsidiaries [Member] | Killen Station [Member] | Dpandl Investment [Member]
Property, Plant and Equipment [Line Items]
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress	$ 1
Jointly Owned Utility Plant, Gross Ownership Amount of Plant in Service	7
Jointly Owned Utility Plant, Ownership Amount of Plant Accumulated Depreciation	$ 1
Subsidiaries [Member] | Killen Station [Member] | Dpandl Share [Member]
Property, Plant and Equipment [Line Items]
Jointly Owned Utility Plant, Proportionate Ownership Share	67.00%
Production Plan Capacity | MW	402
Subsidiaries [Member] | Miami Fort Unit Seven And Eight [Member] | Dpandl Investment [Member]
Property, Plant and Equipment [Line Items]
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress	$ 5
Jointly Owned Utility Plant, Gross Ownership Amount of Plant in Service	28
Jointly Owned Utility Plant, Ownership Amount of Plant Accumulated Depreciation	$ 1
Subsidiaries [Member] | Miami Fort Unit Seven And Eight [Member] | Dpandl Share [Member]
Property, Plant and Equipment [Line Items]
Jointly Owned Utility Plant, Proportionate Ownership Share	36.00%
Production Plan Capacity | MW	368
Subsidiaries [Member] | Stuart Station [Member] | Dpandl Investment [Member]
Property, Plant and Equipment [Line Items]
Write off of net book value	$ 6.4
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress	0
Jointly Owned Utility Plant, Gross Ownership Amount of Plant in Service	1
Jointly Owned Utility Plant, Ownership Amount of Plant Accumulated Depreciation	1
Gain (Loss) on Sale of Assets and Asset Impairment Charges	$ 3.2
Subsidiaries [Member] | Stuart Station [Member] | Dpandl Share [Member]
Property, Plant and Equipment [Line Items]
Jointly Owned Utility Plant, Proportionate Ownership Share	35.00%
Production Plan Capacity | MW	808
Subsidiaries [Member] | Zimmer Station [Member] | Dpandl Investment [Member]
Property, Plant and Equipment [Line Items]
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress	$ 5
Jointly Owned Utility Plant, Gross Ownership Amount of Plant in Service	12
Jointly Owned Utility Plant, Ownership Amount of Plant Accumulated Depreciation	$ 1
Subsidiaries [Member] | Zimmer Station [Member] | Dpandl Share [Member]
Property, Plant and Equipment [Line Items]
Jointly Owned Utility Plant, Proportionate Ownership Share	28.10%
Production Plan Capacity | MW	371
Subsequent Event [Member] | Miami Fort and Zimmer [Member] | Dpandl Investment [Member]
Property, Plant and Equipment [Line Items]
Sale of undivided interest in jointly-owned production units			$ 50
Subsequent Event [Member] | Subsidiaries [Member] | Miami Fort and Zimmer [Member] | Dpandl Investment [Member]
Property, Plant and Equipment [Line Items]
Sale of undivided interest in jointly-owned production units			$ 50

Fair Value (Narrative) (Details

Fair Value (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2017	Dec. 31, 2016
Long-term debt, earliest maturities	2,019
Long-term debt, latest maturities	2,061
Unrealized gains in AOCI, before tax	$ 1.2
Unrealized Gains in AOCI, Net of Tax	0.8
Unrealized Gains and Immaterial Unrealized Losses in AOCI, Before Tax		$ 1
Unrealized gains and immaterial unrealized losses in AOCI, after tax		0.6
Realized gains on investments sold to facilitate the distribution of benefits	0.7
Realized gains on investments sold to facilitate the distribution of benefits, after tax	$ 0.5
Percent of inputs to the fair value of derivative instruments from quoted market prices (percent)	94.00%
Increase (Decrease) in Asset Retirement Obligations	$ 4.4
THE DAYTON POWER AND LIGHT COMPANY [Member]
Long-term debt, earliest maturities	2,020
Long-term debt, latest maturities	2,061
Unrealized gains in AOCI, before tax	$ 1.3
Unrealized Gains in AOCI, Net of Tax	0.9
Unrealized Gains and Immaterial Unrealized Losses in AOCI, Before Tax		1.1
Unrealized gains and immaterial unrealized losses in AOCI, after tax		$ 0.7
Realized gains on investments sold to facilitate the distribution of benefits	0.7
Realized gains on investments sold to facilitate the distribution of benefits, after tax	$ 0.5
Percent of inputs to the fair value of derivative instruments from quoted market prices (percent)	94.00%
Increase (Decrease) in Asset Retirement Obligations	$ 4.4

Fair Value (Fair Value and Cost

Fair Value (Fair Value and Cost of Non-Derivative Instruments) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2017	Dec. 31, 2016
Realized gains on investments sold to facilitate the distribution of benefits, after tax	$ 0.5
Unrealized Gains in AOCI, Net of Tax	0.8
Unrealized Gains and Immaterial Unrealized Losses in AOCI, Before Tax		$ 1
THE DAYTON POWER AND LIGHT COMPANY [Member]
Realized gains on investments sold to facilitate the distribution of benefits, after tax	0.5
Unrealized Gains in AOCI, Net of Tax	0.9
Unrealized Gains and Immaterial Unrealized Losses in AOCI, Before Tax		1.1
Cost [Member]
Total Assets	7.4	7.6
Cost [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Total Assets	7.4	7.6
Fair Value [Member]
Total Master Trust Assets, Fair Value	8.7	8.7
Total Assets	8.7	8.7
Fair Value [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Total Master Trust Assets, Fair Value	8.7	8.7
Total Assets	8.7	8.7
Money Market Funds [Member] | Cost [Member]
Total Master Trust Assets, Cost	0.3	0.4
Money Market Funds [Member] | Cost [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Total Master Trust Assets, Cost	0.3	0.4
Money Market Funds [Member] | Fair Value [Member]
Total Master Trust Assets, Fair Value	0.3	0.4
Money Market Funds [Member] | Fair Value [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Total Master Trust Assets, Fair Value	0.3	0.4
Equity Securities [Member] | Cost [Member]
Total Master Trust Assets, Cost	2.6	2.4
Equity Securities [Member] | Cost [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Total Master Trust Assets, Cost	2.6	2.4
Equity Securities [Member] | Fair Value [Member]
Total Master Trust Assets, Fair Value	3.9	3.4
Equity Securities [Member] | Fair Value [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Total Master Trust Assets, Fair Value	3.9	3.4
Debt Securities [Member] | Cost [Member]
Total Master Trust Assets, Cost	4.3	4.4
Debt Securities [Member] | Cost [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Total Master Trust Assets, Cost	4.3	4.4
Debt Securities [Member] | Fair Value [Member]
Total Master Trust Assets, Fair Value	4.3	4.4
Debt Securities [Member] | Fair Value [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Total Master Trust Assets, Fair Value	4.3	4.4
Hedge Funds [Member] | Cost [Member]
Total Master Trust Assets, Cost	0.1	0
Hedge Funds [Member] | Cost [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Total Master Trust Assets, Cost	0.1	0
Hedge Funds [Member] | Fair Value [Member]
Total Master Trust Assets, Fair Value	0.1	0.1
Hedge Funds [Member] | Fair Value [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Total Master Trust Assets, Fair Value	0.1	0.1
Real Estate Funds [Member] | Cost [Member]
Total Master Trust Assets, Cost	0	0.3
Real Estate Funds [Member] | Cost [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Total Master Trust Assets, Cost	0	0.3
Real Estate Funds [Member] | Fair Value [Member]
Total Master Trust Assets, Fair Value	0	0.3
Real Estate Funds [Member] | Fair Value [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Total Master Trust Assets, Fair Value	0	0.3
Tangible Assets [Member] | Cost [Member]
Total Master Trust Assets, Cost	0.1	0.1
Tangible Assets [Member] | Cost [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Total Master Trust Assets, Cost	0.1	0.1
Tangible Assets [Member] | Fair Value [Member]
Total Master Trust Assets, Fair Value	0.1	0.1
Tangible Assets [Member] | Fair Value [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Total Master Trust Assets, Fair Value	0.1	0.1
Debt [Member] | Cost [Member]
Debt, Cost	1,851.6	1,858
Debt [Member] | Cost [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Debt, Cost	748.3	749
Debt [Member] | Fair Value [Member]
Debt, Fair Value	1,940.7	1,907.7
Debt [Member] | Fair Value [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Debt, Fair Value	$ 762.3	$ 763.5

Fair Value (Fair Value of Asset

Fair Value (Fair Value of Assets and Liabilities Measured on Recurring Basis) (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Level 1 [Member]
Total Master Trust Assets, Fair Value	$ 0.3	$ 0.4
Total Derivative Assets	0.3	0
Total Assets	0.6	0.4
Total Derivative Liabilities	0.5	0
Total Liabilities	0.5	0
Level 1 [Member] | Commodity Contract - FTR [Member]
Total Derivative Assets		0
Level 1 [Member] | Forward Contract Power [Member]
Total Derivative Assets	0	0
Total Derivative Liabilities	0	0
Level 1 [Member] | Interest Rate Contract [Member]
Total Derivative Assets	0	0
Total Derivative Liabilities	0	0
Level 1 [Member] | Natural Gas [Member]
Total Derivative Assets	0.3
Total Derivative Liabilities	0.5
Level 1 [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Total Master Trust Assets, Fair Value	0.3	0.4
Total Derivative Assets	0.3	0
Total Assets	0.6	0.4
Total Derivative Liabilities	0.5	0
Total Liabilities	0.5	0
Level 1 [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | Commodity Contract - FTR [Member]
Total Derivative Assets		0
Level 1 [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | Forward Contract Power [Member]
Total Derivative Assets	0	0
Total Derivative Liabilities	0	0
Level 1 [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | Interest Rate Contract [Member]
Total Derivative Assets	0	0
Total Derivative Liabilities	0	0
Level 1 [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | Natural Gas [Member]
Total Derivative Assets	0.3
Total Derivative Liabilities	0.5
Level 2 [Member]
Total Master Trust Assets, Fair Value	8.4	8.3
Total Derivative Assets	20.3	20.7
Total Assets	28.7	29
Total Derivative Liabilities	17.3	26.7
Total Liabilities	1,940	1,916.4
Level 2 [Member] | Commodity Contract - FTR [Member]
Total Derivative Assets		0
Level 2 [Member] | Forward Contract Power [Member]
Total Derivative Assets	18.9	19.5
Total Derivative Liabilities	17	26
Level 2 [Member] | Interest Rate Contract [Member]
Total Derivative Assets	1.4	1.2
Total Derivative Liabilities	0.3	0.7
Level 2 [Member] | Natural Gas [Member]
Total Derivative Assets	0
Total Derivative Liabilities	0
Level 2 [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Total Master Trust Assets, Fair Value	8.4	8.3
Total Derivative Assets	20.4	20.7
Total Assets	28.8	29
Total Derivative Liabilities	17.3	26.7
Total Liabilities	761.7	772.2
Level 2 [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | Commodity Contract - FTR [Member]
Total Derivative Assets		0
Level 2 [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | Forward Contract Power [Member]
Total Derivative Assets	19	19.5
Total Derivative Liabilities	17	26
Level 2 [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | Interest Rate Contract [Member]
Total Derivative Assets	1.4	1.2
Total Derivative Liabilities	0.3	0.7
Level 2 [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | Natural Gas [Member]
Total Derivative Assets	0
Total Derivative Liabilities	0
Level 3 [Member]
Total Master Trust Assets, Fair Value	0	0
Total Derivative Assets	0	0.1
Total Assets	0	0.1
Total Derivative Liabilities	1.1	2.5
Total Liabilities	19	20.5
Level 3 [Member] | Commodity Contract - FTR [Member]
Total Derivative Assets		0.1
Level 3 [Member] | Forward Contract Power [Member]
Total Derivative Assets	0	0
Total Derivative Liabilities	1.1	2.5
Level 3 [Member] | Interest Rate Contract [Member]
Total Derivative Assets	0	0
Total Derivative Liabilities	0	0
Level 3 [Member] | Natural Gas [Member]
Total Derivative Assets	0
Total Derivative Liabilities	0
Level 3 [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Total Master Trust Assets, Fair Value	0	0
Total Derivative Assets	0	0.1
Total Assets	0	0.1
Total Derivative Liabilities	1.1	2.5
Total Liabilities	19	20.5
Level 3 [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | Commodity Contract - FTR [Member]
Total Derivative Assets		0.1
Level 3 [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | Forward Contract Power [Member]
Total Derivative Assets	0	0
Total Derivative Liabilities	1.1	2.5
Level 3 [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | Interest Rate Contract [Member]
Total Derivative Assets	0	0
Total Derivative Liabilities	0	0
Level 3 [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | Natural Gas [Member]
Total Derivative Assets	0
Total Derivative Liabilities	0
Fair Value [Member]
Total Master Trust Assets, Fair Value	8.7	8.7
Total Derivative Assets	20.6	20.8
Total Assets	29.3	29.5
Total Derivative Liabilities	18.9	29.2
Total Liabilities	1,959.5	1,936.9
Fair Value [Member] | Commodity Contract - FTR [Member]
Total Derivative Assets		0.1
Fair Value [Member] | Forward Contract Power [Member]
Total Derivative Assets	18.9	19.5
Total Derivative Liabilities	18.1	28.5
Fair Value [Member] | Interest Rate Contract [Member]
Total Derivative Assets	1.4	1.2
Total Derivative Liabilities	0.3	0.7
Fair Value [Member] | Natural Gas [Member]
Total Derivative Assets	0.3
Total Derivative Liabilities	0.5
Fair Value [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Total Master Trust Assets, Fair Value	8.7	8.7
Total Derivative Assets	20.7	20.8
Total Assets	29.4	29.5
Total Derivative Liabilities	18.9	29.2
Total Liabilities	781.2	792.7
Fair Value [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | Commodity Contract - FTR [Member]
Total Derivative Assets		0.1
Fair Value [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | Forward Contract Power [Member]
Total Derivative Assets	19	19.5
Total Derivative Liabilities	18.1	28.5
Fair Value [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | Interest Rate Contract [Member]
Total Derivative Assets	1.4	1.2
Total Derivative Liabilities	0.3	0.7
Fair Value [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | Natural Gas [Member]
Total Derivative Assets	0.3
Total Derivative Liabilities	0.5
Money Market Funds [Member] | Level 1 [Member]
Total Master Trust Assets, Fair Value	0.3	0.4
Money Market Funds [Member] | Level 1 [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Total Master Trust Assets, Fair Value	0.3	0.4
Money Market Funds [Member] | Level 2 [Member]
Total Master Trust Assets, Fair Value	0	0
Money Market Funds [Member] | Level 2 [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Total Master Trust Assets, Fair Value	0	0
Money Market Funds [Member] | Level 3 [Member]
Total Master Trust Assets, Fair Value	0	0
Money Market Funds [Member] | Level 3 [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Total Master Trust Assets, Fair Value	0	0
Money Market Funds [Member] | Fair Value [Member]
Total Master Trust Assets, Fair Value	0.3	0.4
Money Market Funds [Member] | Fair Value [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Total Master Trust Assets, Fair Value	0.3	0.4
Equity Securities [Member] | Level 1 [Member]
Total Master Trust Assets, Fair Value	0	0
Equity Securities [Member] | Level 1 [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Total Master Trust Assets, Fair Value	0	0
Equity Securities [Member] | Level 2 [Member]
Total Master Trust Assets, Fair Value	3.9	3.4
Equity Securities [Member] | Level 2 [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Total Master Trust Assets, Fair Value	3.9	3.4
Equity Securities [Member] | Level 3 [Member]
Total Master Trust Assets, Fair Value	0	0
Equity Securities [Member] | Level 3 [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Total Master Trust Assets, Fair Value	0	0
Equity Securities [Member] | Fair Value [Member]
Total Master Trust Assets, Fair Value	3.9	3.4
Equity Securities [Member] | Fair Value [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Total Master Trust Assets, Fair Value	3.9	3.4
Debt Securities [Member] | Level 1 [Member]
Total Master Trust Assets, Fair Value	0	0
Debt Securities [Member] | Level 1 [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Total Master Trust Assets, Fair Value	0	0
Debt Securities [Member] | Level 2 [Member]
Total Master Trust Assets, Fair Value	4.3	4.4
Debt Securities [Member] | Level 2 [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Total Master Trust Assets, Fair Value	4.3	4.4
Debt Securities [Member] | Level 3 [Member]
Total Master Trust Assets, Fair Value	0	0
Debt Securities [Member] | Level 3 [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Total Master Trust Assets, Fair Value	0	0
Debt Securities [Member] | Fair Value [Member]
Total Master Trust Assets, Fair Value	4.3	4.4
Debt Securities [Member] | Fair Value [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Total Master Trust Assets, Fair Value	4.3	4.4
Hedge Funds [Member] | Level 1 [Member]
Total Master Trust Assets, Fair Value	0	0
Hedge Funds [Member] | Level 1 [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Total Master Trust Assets, Fair Value	0	0
Hedge Funds [Member] | Level 2 [Member]
Total Master Trust Assets, Fair Value	0.1	0.1
Hedge Funds [Member] | Level 2 [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Total Master Trust Assets, Fair Value	0.1	0.1
Hedge Funds [Member] | Level 3 [Member]
Total Master Trust Assets, Fair Value	0	0
Hedge Funds [Member] | Level 3 [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Total Master Trust Assets, Fair Value	0	0
Hedge Funds [Member] | Fair Value [Member]
Total Master Trust Assets, Fair Value	0.1	0.1
Hedge Funds [Member] | Fair Value [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Total Master Trust Assets, Fair Value	0.1	0.1
Real Estate Funds [Member] | Level 1 [Member]
Total Master Trust Assets, Fair Value		0
Real Estate Funds [Member] | Level 1 [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Total Master Trust Assets, Fair Value		0
Real Estate Funds [Member] | Level 2 [Member]
Total Master Trust Assets, Fair Value		0.3
Real Estate Funds [Member] | Level 2 [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Total Master Trust Assets, Fair Value		0.3
Real Estate Funds [Member] | Level 3 [Member]
Total Master Trust Assets, Fair Value		0
Real Estate Funds [Member] | Level 3 [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Total Master Trust Assets, Fair Value		0
Real Estate Funds [Member] | Fair Value [Member]
Total Master Trust Assets, Fair Value	0	0.3
Real Estate Funds [Member] | Fair Value [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Total Master Trust Assets, Fair Value	0	0.3
Tangible Assets [Member] | Level 1 [Member]
Total Master Trust Assets, Fair Value	0	0
Tangible Assets [Member] | Level 1 [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Total Master Trust Assets, Fair Value	0
Tangible Assets [Member] | Level 2 [Member]
Total Master Trust Assets, Fair Value	0.1	0.1
Tangible Assets [Member] | Level 2 [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Total Master Trust Assets, Fair Value	0.1	0.1
Tangible Assets [Member] | Level 3 [Member]
Total Master Trust Assets, Fair Value	0	0
Tangible Assets [Member] | Level 3 [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Total Master Trust Assets, Fair Value	0	0
Tangible Assets [Member] | Fair Value [Member]
Total Master Trust Assets, Fair Value	0.1	0.1
Tangible Assets [Member] | Fair Value [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Total Master Trust Assets, Fair Value	0.1	0.1
Debt [Member] | Level 1 [Member]
Debt	0	0
Debt [Member] | Level 1 [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Debt	0	0
Debt [Member] | Level 2 [Member]
Debt	1,922.7	1,889.7
Debt [Member] | Level 2 [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Debt	744.4	745.5
Debt [Member] | Level 3 [Member]
Debt	17.9	18
Debt [Member] | Level 3 [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Debt	17.9	18
Debt [Member] | Fair Value [Member]
Debt	1,940.6	1,907.7
Debt [Member] | Fair Value [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Debt	$ 762.3	$ 763.5

Fair Value Fair Value Measureme

Fair Value Fair Value Measurements (Fair Value of Assets and Liabilities Measured on a Non-recurring Basis) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Increase (Decrease) in Asset Retirement Obligations	$ 4.4
Property, Plant and Equipment, Net	1,700.6		$ 1,767.2
Impairment of Long-Lived Assets Held-for-use	66.4	$ 0
Stuart [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Property, Plant and Equipment, Net	42.4
Impairment of Long-Lived Assets Held-for-use	39.1
Stuart [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Property, Plant, and Equipment, Fair Value Disclosure	0
Stuart [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Property, Plant, and Equipment, Fair Value Disclosure	0
Stuart [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Property, Plant, and Equipment, Fair Value Disclosure	3.3
Killen [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Property, Plant and Equipment, Net	35.2
Impairment of Long-Lived Assets Held-for-use	27.3
Killen [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Property, Plant, and Equipment, Fair Value Disclosure	0
Killen [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Property, Plant, and Equipment, Fair Value Disclosure	0
Killen [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Property, Plant, and Equipment, Fair Value Disclosure	7.9
THE DAYTON POWER AND LIGHT COMPANY [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Increase (Decrease) in Asset Retirement Obligations	4.4
Property, Plant and Equipment, Net	1,370.8		$ 1,440.6
Impairment of Long-Lived Assets Held-for-use	66.3	0
THE DAYTON POWER AND LIGHT COMPANY [Member] | Stuart [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Property, Plant and Equipment, Net	42.3
Impairment of Long-Lived Assets Held-for-use	39
THE DAYTON POWER AND LIGHT COMPANY [Member] | Stuart [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Property, Plant, and Equipment, Fair Value Disclosure	0
THE DAYTON POWER AND LIGHT COMPANY [Member] | Stuart [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Property, Plant, and Equipment, Fair Value Disclosure	0
THE DAYTON POWER AND LIGHT COMPANY [Member] | Stuart [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Property, Plant, and Equipment, Fair Value Disclosure	3.3
THE DAYTON POWER AND LIGHT COMPANY [Member] | Killen [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Property, Plant and Equipment, Net	35.2
Impairment of Long-Lived Assets Held-for-use	27.3
THE DAYTON POWER AND LIGHT COMPANY [Member] | Killen [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Property, Plant, and Equipment, Fair Value Disclosure	0
THE DAYTON POWER AND LIGHT COMPANY [Member] | Killen [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Property, Plant, and Equipment, Fair Value Disclosure	0
THE DAYTON POWER AND LIGHT COMPANY [Member] | Killen [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Property, Plant, and Equipment, Fair Value Disclosure	$ 7.9
Income Approach Valuation Technique [Member] | Weighted Average [Member] | Stuart [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Inputs, Long-term Pre-tax Operating Margin, Percent	10.00%
Fair Value Inputs, Discount Rate	7.00%
Income Approach Valuation Technique [Member] | Weighted Average [Member] | Killen [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Inputs, Long-term Pre-tax Operating Margin, Percent	22.00%
Fair Value Inputs, Discount Rate	7.00%
Income Approach Valuation Technique [Member] | Weighted Average [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | Stuart [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Inputs, Long-term Pre-tax Operating Margin, Percent	10.00%
Fair Value Inputs, Discount Rate	7.00%
Income Approach Valuation Technique [Member] | Weighted Average [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | Killen [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Inputs, Long-term Pre-tax Operating Margin, Percent	22.00%
Fair Value Inputs, Discount Rate	7.00%
Ash ponds, asbestos, river structures and underground storage tanks [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Increase (Decrease) in Asset Retirement Obligations	$ (3.1)	(0.6)
Ash ponds, asbestos, river structures and underground storage tanks [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Increase (Decrease) in Asset Retirement Obligations	$ (2.9)	$ (0.6)

Derivative Instruments and He45

Derivative Instruments and Hedging Activities (Narrative) (Details)	Mar. 31, 2017USD ($)Number_of_interest_rate_swaps	Dec. 31, 2016USD ($)
Additional Collateral, Aggregate Fair Value, OTC Commodity Derivatives	$ 900,000
Fair value of commodity derivative instruments	18,900,000
Collateral Already Posted, Aggregate Fair Value	500,000
Liability position offset by the asset position of counterparties with master netting agreements	14,400,000
Collateral if debt were to fall below investment grade	$ 4,000,000
THE DAYTON POWER AND LIGHT COMPANY [Member]
Debt Instrument, Number of Financial Covenants | Number_of_interest_rate_swaps	2
Additional Collateral, Aggregate Fair Value, OTC Commodity Derivatives	$ 900,000
Fair value of commodity derivative instruments	18,900,000
Collateral Already Posted, Aggregate Fair Value	500,000
Liability position offset by the asset position of counterparties with master netting agreements	14,400,000
Collateral if debt were to fall below investment grade	4,000,000
One Point One Three To One Point One Seven Bonds Maturing In August Two Thousand Twenty [Member]
Long-term Debt, Gross	200,000,000
One Point One Three To One Point One Seven Bonds Maturing In August Two Thousand Twenty [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Long-term Debt, Gross	200,000,000
Interest Rate Swap [Member] | Designated as Hedging Instrument [Member]
Derivative, Notional Amount, Purchase (Sales), Net	200,000,000	$ 200,000,000
Interest Rate Swap [Member] | Designated as Hedging Instrument [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Derivative, Notional Amount, Purchase (Sales), Net	$ 200,000,000	$ 200,000,000

Derivative Instruments and He46

Derivative Instruments and Hedging Activities (Outstanding Derivative Instruments) (Details)	Mar. 31, 2017USD ($)MMBTUMWh	Dec. 31, 2016USD ($)MMBTUMWh
Not Designated as Hedging Instrument [Member] | Commodity Contract - FTR [Member]
Purchase of Units Derivative Instruments Financial Transmission Rights	900	2,300
Sale of Units Derivative Instruments Financial Transmission Rights	0	0
Derivative, Nonmonetary Notional Amount MWh	900	2,300
Not Designated as Hedging Instrument [Member] | Natural Gas [Member]
Purchase of Units Derivative Instruments Natural Gas | MMBTU	17,127,500	1,590,000
Sale of Units Derivative Instruments Natural Gas | MMBTU	0	0
Derivative, Nonmonetary Notional Amount MWh | MMBTU	17,127,500	1,590,000
Not Designated as Hedging Instrument [Member] | Forward Contract Power [Member]
Purchase of Units Derivative Instruments Forward Power Contracts Not Designated as Hedged	1,727,300	2,568,300
Sales of Units Derivative Instruments Forward Power Contracts Not Designated as Hedged	(2,052,600)	(2,020,900)
Derivative, Nonmonetary Notional Amount MWh	(325,300)	547,400
Not Designated as Hedging Instrument [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | Commodity Contract - FTR [Member]
Purchase of Units Derivative Instruments Financial Transmission Rights	900	2,300
Sale of Units Derivative Instruments Financial Transmission Rights	0	0
Derivative, Nonmonetary Notional Amount MWh	900	2,300
Not Designated as Hedging Instrument [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | Natural Gas [Member]
Purchase of Units Derivative Instruments Natural Gas | MMBTU	17,127,500	1,590,000
Sale of Units Derivative Instruments Natural Gas | MMBTU	0	0
Derivative, Nonmonetary Notional Amount MWh | MMBTU	17,127,500	1,590,000
Not Designated as Hedging Instrument [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | Forward Contract Power [Member]
Purchase of Units Derivative Instruments Forward Power Contracts Not Designated as Hedged	1,727,300	2,568,300
Sales of Units Derivative Instruments Forward Power Contracts Not Designated as Hedged	(2,057,900)	(2,037,500)
Derivative, Nonmonetary Notional Amount MWh	(330,600)	530,800
Designated as Hedging Instrument [Member] | Forward Contract Power [Member]
Purchase of Units Derivative Instruments Forward Power Contracts Designated as Cash Flow Hedge	1,276,600	342,900
Sales of Units Derivative Instruments Forward Power Contracts Designated as Cash Flow Hedge	(6,250,900)	(9,974,500)
Derivative, Nonmonetary Notional Amount MWh	(4,974,300)	(9,631,600)
Designated as Hedging Instrument [Member] | Interest Rate Swap [Member]
Purchase of Derivative Instruments Interest Rate Swap | $	$ 200,000,000	$ 200,000,000
Sale of Derivative Instruments Interest Rate Swap | $	0	0
Derivative, Notional Amount, Purchase (Sales), Net | $	$ 200,000,000	$ 200,000,000
Designated as Hedging Instrument [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | Forward Contract Power [Member]
Purchase of Units Derivative Instruments Forward Power Contracts Designated as Cash Flow Hedge	1,276,600	342,900
Sales of Units Derivative Instruments Forward Power Contracts Designated as Cash Flow Hedge	(6,250,900)	(9,974,500)
Derivative, Nonmonetary Notional Amount MWh	(4,974,300)	(9,631,600)
Designated as Hedging Instrument [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | Interest Rate Swap [Member]
Purchase of Derivative Instruments Interest Rate Swap | $	$ 200,000,000	$ 200,000,000
Sale of Derivative Instruments Interest Rate Swap | $	0	0
Derivative, Notional Amount, Purchase (Sales), Net | $	$ 200,000,000	$ 200,000,000

Derivative Instruments and He47

Derivative Instruments and Hedging Activities (Gains or Losses Recognized in AOCI for the Cash Flow Hedges) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Forward Contract Power [Member]
Accumulated Derivative Gain/Loss in AOCI [Roll Forward]
Beginning accumulated derivative gain / (loss) in AOCI	$ (4.3)	$ 9.2
Net gains / (losses) associated with current period hedging transactions	4.9	21.5
Ending accumulated derivative gain / (loss) in AOCI	1.8	22.5
Portion expected to be reclassified to earnings in the next twelve months	$ 2
Maximum length of time that we are hedging our exposure to variability in future cash flows related to forecasted transactions (in months)	17 months
Interest Rate Contract [Member]
Accumulated Derivative Gain/Loss in AOCI [Roll Forward]
Beginning accumulated derivative gain / (loss) in AOCI	$ 17.4	17.5
Net gains / (losses) associated with current period hedging transactions	0.3	0
Ending accumulated derivative gain / (loss) in AOCI	17.5	17.5
Portion expected to be reclassified to earnings in the next twelve months	$ (0.2)
Maximum length of time that we are hedging our exposure to variability in future cash flows related to forecasted transactions (in months)	41 months
THE DAYTON POWER AND LIGHT COMPANY [Member] | Forward Contract Power [Member]
Accumulated Derivative Gain/Loss in AOCI [Roll Forward]
Beginning accumulated derivative gain / (loss) in AOCI	$ (4.3)	9.2
Net gains / (losses) associated with current period hedging transactions	4.9	21.5
Ending accumulated derivative gain / (loss) in AOCI	1.8	22.5
Portion expected to be reclassified to earnings in the next twelve months	$ 2
Maximum length of time that we are hedging our exposure to variability in future cash flows related to forecasted transactions (in months)	17 months
THE DAYTON POWER AND LIGHT COMPANY [Member] | Interest Rate Contract [Member]
Accumulated Derivative Gain/Loss in AOCI [Roll Forward]
Beginning accumulated derivative gain / (loss) in AOCI	$ 1.6	2
Net gains / (losses) associated with current period hedging transactions	0.3	0
Ending accumulated derivative gain / (loss) in AOCI	1.7	1.8
Portion expected to be reclassified to earnings in the next twelve months	$ (0.2)
Maximum length of time that we are hedging our exposure to variability in future cash flows related to forecasted transactions (in months)	41 months
Interest Expense [Member] | Forward Contract Power [Member]
Accumulated Derivative Gain/Loss in AOCI [Roll Forward]
Net gains losses reclassified to earnings	$ 0	0
Interest Expense [Member] | Interest Rate Contract [Member]
Accumulated Derivative Gain/Loss in AOCI [Roll Forward]
Net gains losses reclassified to earnings	(0.2)	0
Interest Expense [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | Forward Contract Power [Member]
Accumulated Derivative Gain/Loss in AOCI [Roll Forward]
Net gains losses reclassified to earnings	0	0
Interest Expense [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | Interest Rate Contract [Member]
Accumulated Derivative Gain/Loss in AOCI [Roll Forward]
Net gains losses reclassified to earnings	(0.2)	(0.2)
Revenue [Member] | Forward Contract Power [Member]
Accumulated Derivative Gain/Loss in AOCI [Roll Forward]
Net gains losses reclassified to earnings	(0.9)	(11)
Revenue [Member] | Interest Rate Contract [Member]
Accumulated Derivative Gain/Loss in AOCI [Roll Forward]
Net gains losses reclassified to earnings	0	0
Revenue [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | Forward Contract Power [Member]
Accumulated Derivative Gain/Loss in AOCI [Roll Forward]
Net gains losses reclassified to earnings	(0.9)	(11)
Revenue [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | Interest Rate Contract [Member]
Accumulated Derivative Gain/Loss in AOCI [Roll Forward]
Net gains losses reclassified to earnings	0	0
Purchased Power [Member] | Forward Contract Power [Member]
Accumulated Derivative Gain/Loss in AOCI [Roll Forward]
Net gains losses reclassified to earnings	2.1	2.8
Purchased Power [Member] | Interest Rate Contract [Member]
Accumulated Derivative Gain/Loss in AOCI [Roll Forward]
Net gains losses reclassified to earnings	0	0
Purchased Power [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | Forward Contract Power [Member]
Accumulated Derivative Gain/Loss in AOCI [Roll Forward]
Net gains losses reclassified to earnings	2.1	2.8
Purchased Power [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | Interest Rate Contract [Member]
Accumulated Derivative Gain/Loss in AOCI [Roll Forward]
Net gains losses reclassified to earnings	$ 0	$ 0

Derivative Instruments and He48

Derivative Instruments and Hedging Activities (Classification within the Condensed Consolidated Statements of Results of Operations or Balance Sheets of the Gains and Losses) (Details) - Not Designated as Hedging Instrument [Member] - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Change in unrealized gain / (loss)	$ (0.2)	$ (1.6)
Realized loss	(2.6)	(0.4)
Derivative, Gain (Loss) on Derivative, Net	(2.8)	(2)
Commodity Contract - FTR [Member]
Change in unrealized gain / (loss)	0	0.1
Realized loss	0.2	0.2
Derivative, Gain (Loss) on Derivative, Net	0.2	0.3
Forward Contract Power [Member]
Change in unrealized gain / (loss)	(0.1)	(1.5)
Realized loss	(2.6)	(0.4)
Derivative, Gain (Loss) on Derivative, Net	(2.7)	(1.9)
Natural Gas [Member]
Change in unrealized gain / (loss)	(0.1)	(0.2)
Realized loss	(0.2)	(0.2)
Derivative, Gain (Loss) on Derivative, Net	(0.3)	(0.4)
THE DAYTON POWER AND LIGHT COMPANY [Member]
Change in unrealized gain / (loss)	(0.2)	(2)
Realized loss	(2.6)	(0.3)
Derivative, Gain (Loss) on Derivative, Net	(2.8)	(2.3)
THE DAYTON POWER AND LIGHT COMPANY [Member] | Commodity Contract - FTR [Member]
Change in unrealized gain / (loss)	0	0.1
Realized loss	0.2	0.2
Derivative, Gain (Loss) on Derivative, Net	0.2	0.3
THE DAYTON POWER AND LIGHT COMPANY [Member] | Forward Contract Power [Member]
Change in unrealized gain / (loss)	(0.1)	(1.9)
Realized loss	(2.6)	(0.3)
Derivative, Gain (Loss) on Derivative, Net	(2.7)	(2.2)
THE DAYTON POWER AND LIGHT COMPANY [Member] | Natural Gas [Member]
Change in unrealized gain / (loss)	(0.1)	(0.2)
Realized loss	(0.2)	(0.2)
Derivative, Gain (Loss) on Derivative, Net	(0.3)	(0.4)
Revenue [Member]
Derivative, Gain (Loss) on Derivative, Net	(6.7)	(1.1)
Revenue [Member] | Commodity Contract - FTR [Member]
Derivative, Gain (Loss) on Derivative, Net	0	0
Revenue [Member] | Forward Contract Power [Member]
Derivative, Gain (Loss) on Derivative, Net	(6.7)	(1.1)
Revenue [Member] | Natural Gas [Member]
Derivative, Gain (Loss) on Derivative, Net	0	0
Revenue [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Derivative, Gain (Loss) on Derivative, Net	(6.7)	(1.4)
Revenue [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | Commodity Contract - FTR [Member]
Derivative, Gain (Loss) on Derivative, Net	0	0
Revenue [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | Forward Contract Power [Member]
Derivative, Gain (Loss) on Derivative, Net	(6.7)	(1.4)
Revenue [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | Natural Gas [Member]
Derivative, Gain (Loss) on Derivative, Net	0	0
Purchased Power [Member]
Derivative, Gain (Loss) on Derivative, Net	3.9	(0.9)
Purchased Power [Member] | Commodity Contract - FTR [Member]
Derivative, Gain (Loss) on Derivative, Net	0.2	0.3
Purchased Power [Member] | Forward Contract Power [Member]
Derivative, Gain (Loss) on Derivative, Net	4	(0.8)
Purchased Power [Member] | Natural Gas [Member]
Derivative, Gain (Loss) on Derivative, Net	(0.3)	(0.4)
Purchased Power [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Derivative, Gain (Loss) on Derivative, Net	3.9	(0.9)
Purchased Power [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | Commodity Contract - FTR [Member]
Derivative, Gain (Loss) on Derivative, Net	0.2	0.3
Purchased Power [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | Forward Contract Power [Member]
Derivative, Gain (Loss) on Derivative, Net	4	(0.8)
Purchased Power [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | Natural Gas [Member]
Derivative, Gain (Loss) on Derivative, Net	$ (0.3)	$ (0.4)

Derivative Instruments and He49

Derivative Instruments and Hedging Activities (Fair Value and Balance Sheet Location (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Derivative Liability, Fair Value	$ 18.9
Liability position offset by the asset position of counterparties with master netting agreements	14.4
THE DAYTON POWER AND LIGHT COMPANY [Member]
Derivative Liability, Fair Value	18.9
Liability position offset by the asset position of counterparties with master netting agreements	14.4
Total Assets [Member]
Derivative Asset, Fair Value	20.6	$ 20.8
Derivative, Collateral, Obligation to Return Securities	(14.4)	(16.8)
Derivative, Collateral, Obligation to Return Cash	0	0
Derivative Asset, Fair Value, Amount Offset Against Collateral	6.2	4
Total Assets [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Derivative Asset, Fair Value	20.7	20.8
Derivative, Collateral, Obligation to Return Securities	(14.4)	(16.8)
Derivative, Collateral, Obligation to Return Cash	0	0
Derivative Asset, Fair Value, Amount Offset Against Collateral	6.3	4
Total Liabilities [Member]
Derivative Liability, Fair Value	18.9	29.2
Derivative, Collateral, Right to Reclaim Securities	(14.4)	(16.8)
Derivative, Collateral, Right to Reclaim Cash	(0.5)	(6.3)
Liability position offset by the asset position of counterparties with master netting agreements	4	6.1
Total Liabilities [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Derivative Liability, Fair Value	18.9	29.2
Derivative, Collateral, Right to Reclaim Securities	(14.4)	(16.8)
Derivative, Collateral, Right to Reclaim Cash	(0.5)	(6.3)
Liability position offset by the asset position of counterparties with master netting agreements	4	6.1
Cash Flow Hedging [Member] | Forward Contract Power [Member] | Short-term Derivative Positions [Member] | Other Prepayments and Current Assets [Member]
Derivative Asset, Fair Value	12.7	11
Derivative, Collateral, Obligation to Return Securities	(8.6)	(10.5)
Derivative, Collateral, Obligation to Return Cash	0	0
Derivative Asset, Fair Value, Amount Offset Against Collateral	4.1	0.5
Cash Flow Hedging [Member] | Forward Contract Power [Member] | Short-term Derivative Positions [Member] | Other Prepayments and Current Assets [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Derivative Asset, Fair Value	12.7	11
Derivative, Collateral, Obligation to Return Securities	(8.6)	(10.5)
Derivative, Collateral, Obligation to Return Cash	0	0
Derivative Asset, Fair Value, Amount Offset Against Collateral	4.1	0.5
Cash Flow Hedging [Member] | Forward Contract Power [Member] | Short-term Derivative Positions [Member] | Other Current Liabilities [Member]
Derivative Liability, Fair Value	9.7	16.4
Derivative, Collateral, Right to Reclaim Securities	(8.6)	(10.5)
Derivative, Collateral, Right to Reclaim Cash	0	(5.5)
Liability position offset by the asset position of counterparties with master netting agreements	1.1	0.4
Cash Flow Hedging [Member] | Forward Contract Power [Member] | Short-term Derivative Positions [Member] | Other Current Liabilities [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Derivative Liability, Fair Value	9.7	16.4
Derivative, Collateral, Right to Reclaim Securities	(8.6)	(10.5)
Derivative, Collateral, Right to Reclaim Cash	0	(5.5)
Liability position offset by the asset position of counterparties with master netting agreements	1.1	0.4
Cash Flow Hedging [Member] | Forward Contract Power [Member] | Long-term Derivative Positions [Member] | Other Deferred Asset [Member]
Derivative Asset, Fair Value		0.6
Derivative, Collateral, Obligation to Return Securities		(0.6)
Derivative, Collateral, Obligation to Return Cash		0
Derivative Asset, Fair Value, Amount Offset Against Collateral		0
Cash Flow Hedging [Member] | Forward Contract Power [Member] | Long-term Derivative Positions [Member] | Other Deferred Asset [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Derivative Asset, Fair Value		0.6
Derivative, Collateral, Obligation to Return Securities		(0.6)
Derivative, Collateral, Obligation to Return Cash		0
Derivative Asset, Fair Value, Amount Offset Against Collateral		0
Cash Flow Hedging [Member] | Forward Contract Power [Member] | Long-term Derivative Positions [Member] | Other Deferred Credit [Member]
Derivative Liability, Fair Value	0.1	2.4
Derivative, Collateral, Right to Reclaim Securities	0	(0.6)
Derivative, Collateral, Right to Reclaim Cash	(0.1)	(0.8)
Liability position offset by the asset position of counterparties with master netting agreements	0	1
Cash Flow Hedging [Member] | Forward Contract Power [Member] | Long-term Derivative Positions [Member] | Other Deferred Credit [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Derivative Liability, Fair Value	0.1	2.4
Derivative, Collateral, Right to Reclaim Securities	0	(0.6)
Derivative, Collateral, Right to Reclaim Cash	(0.1)	(0.8)
Liability position offset by the asset position of counterparties with master netting agreements	0	1
Cash Flow Hedging [Member] | Interest Rate Swap [Member] | Short-term Derivative Positions [Member] | Other Current Liabilities [Member]
Derivative Liability, Fair Value		0.7
Derivative, Collateral, Right to Reclaim Securities		0
Derivative, Collateral, Right to Reclaim Cash		0
Liability position offset by the asset position of counterparties with master netting agreements		0.7
Cash Flow Hedging [Member] | Interest Rate Swap [Member] | Short-term Derivative Positions [Member] | Other Current Liabilities [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Derivative Liability, Fair Value		0.7
Derivative, Collateral, Right to Reclaim Securities		0
Derivative, Collateral, Right to Reclaim Cash		0
Liability position offset by the asset position of counterparties with master netting agreements		0.7
Cash Flow Hedging [Member] | Interest Rate Swap [Member] | Long-term Derivative Positions [Member] | Other Deferred Asset [Member]
Derivative Asset, Fair Value	1.4	1.2
Derivative, Collateral, Obligation to Return Securities	0	0
Derivative, Collateral, Obligation to Return Cash	0	0
Derivative Asset, Fair Value, Amount Offset Against Collateral	1.4	1.2
Cash Flow Hedging [Member] | Interest Rate Swap [Member] | Long-term Derivative Positions [Member] | Other Deferred Asset [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Derivative Asset, Fair Value	1.4	1.2
Derivative, Collateral, Obligation to Return Securities	0	0
Derivative, Collateral, Obligation to Return Cash	0	0
Derivative Asset, Fair Value, Amount Offset Against Collateral	1.4	1.2
Fair Value Hedging [Member] | Commodity Contract - FTR [Member] | Short-term Derivative Positions [Member] | Other Prepayments and Current Assets [Member]
Derivative Asset, Fair Value		0.1
Derivative, Collateral, Obligation to Return Securities		0
Derivative, Collateral, Obligation to Return Cash		0
Derivative Asset, Fair Value, Amount Offset Against Collateral		0.1
Fair Value Hedging [Member] | Commodity Contract - FTR [Member] | Short-term Derivative Positions [Member] | Other Prepayments and Current Assets [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Derivative Asset, Fair Value		0.1
Derivative, Collateral, Obligation to Return Securities		0
Derivative, Collateral, Obligation to Return Cash		0
Derivative Asset, Fair Value, Amount Offset Against Collateral		0.1
Fair Value Hedging [Member] | Natural Gas [Member] | Short-term Derivative Positions [Member] | Other Current Liabilities [Member]
Derivative Liability, Fair Value	0.2
Derivative, Collateral, Right to Reclaim Securities	(0.2)
Derivative, Collateral, Right to Reclaim Cash	0
Liability position offset by the asset position of counterparties with master netting agreements	0
Fair Value Hedging [Member] | Natural Gas [Member] | Short-term Derivative Positions [Member] | Other Current Liabilities [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Derivative Liability, Fair Value	0.2
Derivative, Collateral, Right to Reclaim Securities	(0.2)
Derivative, Collateral, Right to Reclaim Cash	0
Liability position offset by the asset position of counterparties with master netting agreements	0
Fair Value Hedging [Member] | Forward Contract Power [Member] | Short-term Derivative Positions [Member] | Other Prepayments and Current Assets [Member]
Derivative Asset, Fair Value	6.1	6
Derivative, Collateral, Obligation to Return Securities	(5.5)	(4.7)
Derivative, Collateral, Obligation to Return Cash	0	0
Derivative Asset, Fair Value, Amount Offset Against Collateral	0.6	1.3
Fair Value Hedging [Member] | Forward Contract Power [Member] | Short-term Derivative Positions [Member] | Other Prepayments and Current Assets [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Derivative Asset, Fair Value	6.2	6
Derivative, Collateral, Obligation to Return Securities	(5.5)	(4.7)
Derivative, Collateral, Obligation to Return Cash	0	0
Derivative Asset, Fair Value, Amount Offset Against Collateral	0.7	1.3
Fair Value Hedging [Member] | Forward Contract Power [Member] | Short-term Derivative Positions [Member] | Other Current Liabilities [Member]
Derivative Liability, Fair Value	8.1	7.7
Derivative, Collateral, Right to Reclaim Securities	(5.5)	(4.7)
Derivative, Collateral, Right to Reclaim Cash	(0.1)	0
Liability position offset by the asset position of counterparties with master netting agreements	2.5	3
Fair Value Hedging [Member] | Forward Contract Power [Member] | Short-term Derivative Positions [Member] | Other Current Liabilities [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Derivative Liability, Fair Value	8.1	7.7
Derivative, Collateral, Right to Reclaim Securities	(5.5)	(4.7)
Derivative, Collateral, Right to Reclaim Cash	(0.1)	0
Liability position offset by the asset position of counterparties with master netting agreements	2.5	3
Fair Value Hedging [Member] | Forward Contract Power [Member] | Long-term Derivative Positions [Member] | Other Deferred Asset [Member]
Derivative Asset, Fair Value	0.1	1.9
Derivative, Collateral, Obligation to Return Securities	(0.1)	(1)
Derivative, Collateral, Obligation to Return Cash	0	0
Derivative Asset, Fair Value, Amount Offset Against Collateral	0	0.9
Fair Value Hedging [Member] | Forward Contract Power [Member] | Long-term Derivative Positions [Member] | Other Deferred Asset [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Derivative Asset, Fair Value	0.1	1.9
Derivative, Collateral, Obligation to Return Securities	(0.1)	(1)
Derivative, Collateral, Obligation to Return Cash	0	0
Derivative Asset, Fair Value, Amount Offset Against Collateral	0	0.9
Fair Value Hedging [Member] | Forward Contract Power [Member] | Long-term Derivative Positions [Member] | Other Deferred Credit [Member]
Derivative Liability, Fair Value		2
Derivative, Collateral, Right to Reclaim Securities		(1)
Derivative, Collateral, Right to Reclaim Cash		0
Liability position offset by the asset position of counterparties with master netting agreements		1
Fair Value Hedging [Member] | Forward Contract Power [Member] | Long-term Derivative Positions [Member] | Other Deferred Credit [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Derivative Liability, Fair Value	0.2	2
Derivative, Collateral, Right to Reclaim Securities	(0.1)	(1)
Derivative, Collateral, Right to Reclaim Cash	0	0
Liability position offset by the asset position of counterparties with master netting agreements	0.1	$ 1
Fair Value Hedging [Member] | Natural Gas Futures [Member] | Short-term Derivative Positions [Member] | Other Prepayments and Current Assets [Member]
Derivative Asset, Fair Value	0.3
Derivative, Collateral, Obligation to Return Securities	(0.2)
Derivative, Collateral, Obligation to Return Cash	0
Derivative Asset, Fair Value, Amount Offset Against Collateral	0.1
Fair Value Hedging [Member] | Natural Gas Futures [Member] | Short-term Derivative Positions [Member] | Other Prepayments and Current Assets [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Derivative Asset, Fair Value	0.3
Derivative, Collateral, Obligation to Return Securities	(0.2)
Derivative, Collateral, Obligation to Return Cash	0
Derivative Asset, Fair Value, Amount Offset Against Collateral	0.1
Designated as Hedging Instrument [Member] | Interest Rate Swap [Member] | Short-term Derivative Positions [Member] | Other Current Liabilities [Member]
Derivative Liability, Fair Value	0.3
Derivative, Collateral, Right to Reclaim Securities	0
Derivative, Collateral, Right to Reclaim Cash	0
Liability position offset by the asset position of counterparties with master netting agreements	0.3
Designated as Hedging Instrument [Member] | Interest Rate Swap [Member] | Short-term Derivative Positions [Member] | Other Current Liabilities [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Derivative Liability, Fair Value	0.3
Derivative, Collateral, Right to Reclaim Securities	0
Derivative, Collateral, Right to Reclaim Cash	0
Liability position offset by the asset position of counterparties with master netting agreements	0.3
Not Designated as Hedging Instrument [Member] | Forward Contract Power [Member] | Long-term Derivative Positions [Member] | Other Deferred Credit [Member]
Derivative Liability, Fair Value	0.2
Derivative, Collateral, Right to Reclaim Securities	(0.1)
Derivative, Collateral, Right to Reclaim Cash	0
Liability position offset by the asset position of counterparties with master netting agreements	0.1
Not Designated as Hedging Instrument [Member] | Natural Gas Futures [Member] | Long-term Derivative Positions [Member] | Other Deferred Credit [Member]
Derivative Liability, Fair Value	0.3
Derivative, Collateral, Right to Reclaim Securities	0
Derivative, Collateral, Right to Reclaim Cash	(0.3)
Liability position offset by the asset position of counterparties with master netting agreements	0
Not Designated as Hedging Instrument [Member] | Natural Gas Futures [Member] | Long-term Derivative Positions [Member] | Other Deferred Credit [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Derivative Liability, Fair Value	0.3
Derivative, Collateral, Right to Reclaim Securities	0
Derivative, Collateral, Right to Reclaim Cash	(0.3)
Liability position offset by the asset position of counterparties with master netting agreements	$ 0

Debt (Narrative) (Details)

Debt (Narrative) (Details)	Feb. 05, 2016	Mar. 31, 2017USD ($)fiscal_quarterdebt_covenant	Mar. 31, 2016USD ($)	Jun. 30, 2018USD ($)	Dec. 31, 2016USD ($)
Debt Instrument [Line Items]
Retirement of long-term debt		$ 7,400,000	$ 75,400,000
Total Debt to Total Capitalization Ratio		0.53
THE DAYTON POWER AND LIGHT COMPANY [Member]
Debt Instrument [Line Items]
Retirement of long-term debt		$ 1,100,000	$ 0
Total Debt to Total Capitalization Ratio		0.53
Senior unsecured due in October 2016 - 6.5% [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate	0.50%
Term Loan Maturing 2022 [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		$ 443,900,000			$ 445,000,000
Term Loan Maturing 2022 [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		$ 443,900,000			$ 445,000,000
Revolving Credit Agreement and Standby Letters of Credit [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Debt Instrument [Line Items]
Number of financial covenants | debt_covenant		2
Number of prior quarters included in EBITDA to interest calculation | fiscal_quarter		4
DPL Revolving Credit Agreement and Term Loan Maturing July 2020 [Member]
Debt Instrument [Line Items]
Number of financial covenants | debt_covenant		2
Number of prior quarters included in EBITDA to interest calculation | fiscal_quarter		4
Number of prior quarters included in debt to EBITDA ratio | fiscal_quarter		4
Subsequent Event [Member]
Debt Instrument [Line Items]
Long Term Indebtedness, Less than or Equal to				$ 750,000,000
Subsequent Event [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Debt Instrument [Line Items]
Long Term Indebtedness, Less than or Equal to				$ 750,000,000

Debt (Long-term Debt) (Details)

Debt (Long-term Debt) (Details) - USD ($) $ in Millions	Feb. 05, 2016	Mar. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Capital Lease Obligations		$ 0.4	$ 0.4
Unamortized deferred finance costs		(10.1)	(10.7)
Unamortized deferred finance costs		(8.4)	(8.8)
Unamortized debt discount and premiums, net		(0.8)	(0.6)
Total long-term debt at subsidiary		746.8	747.2
Total long-term debt		1,852	1,858.4
Less: current portion		(29.7)	(29.7)
Long-term debt		$ 1,822.3	1,828.7
Long-term debt, earliest maturities		2,019
Long-term debt, latest maturities		2,061
THE DAYTON POWER AND LIGHT COMPANY [Member]
Debt Instrument [Line Items]
Capital Lease Obligations		$ 0.4	0.4
Unamortized deferred finance costs		(11.5)	(11.8)
Unamortized debt discount and premiums, net		(5.3)	(5.5)
Unamortized debt discount		(2)	(2.2)
Total long-term debt		748.7	749.4
Less: current portion		(4.7)	(4.7)
Long-term debt		$ 744	744.7
Long-term debt, earliest maturities		2,020
Long-term debt, latest maturities		2,061
Term Loan Maturing 2022 [Domain]
Debt Instrument [Line Items]
Debt instrument maturity year		Aug. 24, 2022
Term Loan Maturing 2022 [Domain] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Debt Instrument [Line Items]
Debt instrument maturity year		Aug. 24, 2022
Term Loan Maturing 2022 [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		$ 443.9	$ 445
Debt Instrument, Interest Rate, Effective Percentage Rate Range, Minimum		4.00%	4.00%
Debt instrument interest percentage maximum		4.00%
Debt Instrument, Interest Rate, Effective Percentage Rate Range, Maximum			4.00%
Term Loan Maturing 2022 [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		$ 443.9	$ 445
Debt Instrument, Interest Rate, Effective Percentage Rate Range, Minimum		4.01%	4.00%
Debt instrument interest percentage maximum		4.04%
Debt Instrument, Interest Rate, Effective Percentage Rate Range, Maximum			4.01%
Pollution Control Series Maturing in September 2036 - 4.80% [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		$ 100	$ 100
Debt instrument maturity year		Sep. 1, 2036
Debt instrument interest percentage		4.80%
Pollution Control Series Maturing in September 2036 - 4.80% [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		$ 100	$ 100
Debt instrument maturity year		Sep. 1, 2036
Debt instrument interest percentage		4.80%
Pollution Control Series Maturing in August 2020 - 1.13% - 1.14% [Member]
Debt Instrument [Line Items]
Debt instrument maturity year		Aug. 1, 2020
Debt instrument interest percentage minimum			1.29%
Debt instrument interest percentage maximum			1.42%
Pollution Control Series Maturing in August 2020 - 1.13% - 1.14% [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		$ 200	$ 200
Debt instrument maturity year		Aug. 1, 2020
Zero Point Two Three To Zero Point Two Nine And Zero Point One Six To Zero Point Three Six Percentage Of Bonds Maturing In November Two Thousand Forty [Member]
Debt Instrument [Line Items]
Debt instrument interest percentage minimum		1.52%
Debt instrument interest percentage maximum		1.53%
Zero Point Two Three To Zero Point Two Nine And Zero Point One Six To Zero Point Three Six Percentage Of Bonds Maturing In November Two Thousand Forty [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Debt Instrument [Line Items]
Debt instrument interest percentage minimum		1.52%	1.29%
Debt instrument interest percentage maximum		1.53%	1.42%
U.S. Government note maturing in February 2061 - 4.20% [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		$ 17.9	$ 18
Debt instrument maturity year		Feb. 1, 2061
Debt instrument interest percentage		4.20%
U.S. Government note maturing in February 2061 - 4.20% [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		$ 17.9	18
Debt instrument maturity year		Feb. 1, 2061
Debt instrument interest percentage		4.20%
Bank term loan due in July 2020 - rates from: 2.44% - 2.45% [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		$ 118.8	$ 125
Debt instrument maturity year		Jul. 31, 2020
Debt instrument interest percentage minimum		3.02%	2.67%
Debt instrument interest percentage maximum		3.73%	3.02%
Senior unsecured due in October 2016 - 6.5% [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate	0.50%
Senior unsecured due in October 2019 - 6.75% [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		$ 200	$ 200
Debt instrument maturity year		Oct. 1, 2019
Debt instrument interest percentage		6.75%
Senior unsecured due in October 2021 - 7.25% [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		$ 780	780
Debt instrument maturity year		Oct. 1, 2021
Debt instrument interest percentage		7.25%
Note to DPL Capital Trust II Maturing in September 2031 - 8.125% [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		$ 15.6	$ 15.6
Debt instrument maturity year		Sep. 1, 2031
Debt instrument interest percentage		8.125%

Income Taxes (Narrative) (Detai

Income Taxes (Narrative) (Details)	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Entity Information [Line Items]
Effective income tax rates	37.90%	21.40%
Estimated annual effective income tax rate	37.60%	20.60%
THE DAYTON POWER AND LIGHT COMPANY [Member]
Entity Information [Line Items]
Effective income tax rates	34.40%	26.90%
Estimated annual effective income tax rate	33.80%	27.00%

Benefit Plans (Net Periodic Ben

Benefit Plans (Net Periodic Benefit Cost (Income)) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Pension [Member]
Contributions by employer	$ 5	$ 5
Service cost	1.4	1.4
Interest cost	3.6	3.7
Expected return on assets	(5.7)	(5.7)
Defined Benefit Plan, Curtailments	(4.1)	0
Prior service cost	0.4	0.5
Actuarial loss / (gain)	1.3	1
Net periodic benefit cost	5.1	0.9
Postretirement [Member]
Defined Benefit Plan, Funded Status of Plan	15.8		$ 15.8
Postretirement Health Coverage [Member]
Defined Benefit Plan, Benefit Obligation	7		6.8
THE DAYTON POWER AND LIGHT COMPANY [Member] | Pension [Member]
Contributions by employer	5	5
Service cost	1.4	1.4
Interest cost	3.6	3.7
Expected return on assets	(5.7)	(5.7)
Defined Benefit Plan, Curtailments	(5.6)	0
Prior service cost	0.5	0.8
Actuarial loss / (gain)	2.2	1.8
Net periodic benefit cost	7.6	$ 2
THE DAYTON POWER AND LIGHT COMPANY [Member] | Postretirement [Member]
Defined Benefit Plan, Funded Status of Plan	15.8		15.8
THE DAYTON POWER AND LIGHT COMPANY [Member] | Postretirement Health Coverage [Member]
Defined Benefit Plan, Benefit Obligation	$ 7		$ 6.8

Benefit Plans (Estimated Future

Benefit Plans (Estimated Future Benefit Payments and Medicare Part D Reimbursements) (Details) - Pension [Member] $ in Millions	Mar. 31, 2017USD ($)
2,016	$ 18.8
2,017	25.5
2,018	26
2,019	26.4
2,020	26.7
2021 - 2025	139.6
THE DAYTON POWER AND LIGHT COMPANY [Member]
2,016	18.8
2,017	25.5
2,018	26
2,019	26.4
2,020	26.7
2021 - 2025	$ 139.6

Shareholder's Equity (Details)

Shareholder's Equity (Details) - USD ($)	3 Months Ended
	Mar. 31, 2017	Dec. 31, 2016
Class of Stock [Line Items]
Accounts Payable, Related Parties, Current	$ 0	$ 2,000,000
Common stock, shares authorized	1,500	1,500
Common stock, shares outstanding	1	1
THE DAYTON POWER AND LIGHT COMPANY [Member]
Class of Stock [Line Items]
Accounts Payable, Related Parties, Current	$ 0	$ 2,000,000
Common stock, shares authorized	250,000,000
Par value common shares (in USD per share)	$ 0.01	$ 0.01
Common stock, shares outstanding	41,172,173
PUCO merger equity ratio approval (at least)	50.00%
PUCO Equity Ratio	30.00%
PUCO merger, maximum long-term debt allowed	$ 750,000,000
PUCO merger, maximum long-term debt as percent of rate base (percent)	75.00%

Shareholder's Equity Equity Set

Shareholder's Equity Equity Settlement of Related Party Payable (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Accounts Payable, Related Parties, Current	$ 0	$ 2
Subsidiaries [Member]
Accounts Payable, Related Parties, Current	$ 0	$ 2

Contractual Obligations, Comm57

Contractual Obligations, Commercial Commitments and Contingencies (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Dec. 31, 2016
Public Utility, Property, Plant and Equipment [Line Items]
Due to third parties, current	$ 2.4	$ 2.3
THE DAYTON POWER AND LIGHT COMPANY [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Debt maturity, earliest	2,018
Debt maturity, latest	2,040
DPLE [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Third party guarantees	$ 24.6
Debt Obligation on 4.9% Equity Ownership [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Equity ownership interest	4.90%
Equity ownership interest aggregate cost	$ 72.5
Electric Generation Company [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Debt obligation	$ 1,479.6

Related Party Transactions (Det

Related Party Transactions (Details) - USD ($) $ in Millions	Dec. 31, 2016	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Related Party Transaction [Line Items]
Charges for services provided		$ 13.9	$ 11.6
Sales to related party		1	1.2
Net payable to the Service Company	$ (2)	0		$ (2)
Investment in trust	$ 0.3	0.3		0.3
Debt Instrument, Interest Rate, Stated Percentage	3.02%
Due to Affiliate	$ (2.5)	(3.1)		(2.5)
Note to DPL Capital Trust II Maturing in September 2031 - 8.125% [Member]
Related Party Transaction [Line Items]
Note payable to trust	15.6	15.6		15.6
Prepaid Expenses and Other Current Assets [Member]
Related Party Transaction [Line Items]
Accounts Receivable, Related Parties, Current
Accrued Liabilities [Member]
Related Party Transaction [Line Items]
Net payable to the Service Company	(97.2)	(70.6)		(97.2)
Charges for health, welfare and benefit plans [Member] | Subsidiary of Common Parent [Member]
Related Party Transaction [Line Items]
Transactions with other AES affiliates		4.2	4.1
THE DAYTON POWER AND LIGHT COMPANY [Member]
Related Party Transaction [Line Items]
Charges for services provided		13	8.9
Sales to related party		1	1.2
Premiums paid for insurance services provided by MVIC		(0.8)	(0.9)
Net payable to the Service Company	(2)	0		(2)
Gain on termination of contract		0	27.7
Notes Payable, Related Parties		(30)	(5)	(5)
Notes Payable, Related Parties	5	0		5
Due to Affiliate	(2.5)	5		(2.5)
THE DAYTON POWER AND LIGHT COMPANY [Member] | Prepaid Expenses and Other Current Assets [Member]
Related Party Transaction [Line Items]
Accounts Receivable, Related Parties, Current	9.5	23.7		9.5
THE DAYTON POWER AND LIGHT COMPANY [Member] | Accrued Liabilities [Member]
Related Party Transaction [Line Items]
Net payable to the Service Company
THE DAYTON POWER AND LIGHT COMPANY [Member] | Insurance Proceeds Received [Member] | Subsidiary of Common Parent [Member]
Related Party Transaction [Line Items]
Transactions with other AES affiliates		0	0.2
THE DAYTON POWER AND LIGHT COMPANY [Member] | Charges for health, welfare and benefit plans [Member] | Subsidiary of Common Parent [Member]
Related Party Transaction [Line Items]
Transactions with other AES affiliates		$ 4.1	$ 4.1

Business Segments (Narrative) (

Business Segments (Narrative) (Details) - THE DAYTON POWER AND LIGHT COMPANY [Member]	3 Months Ended
	Mar. 31, 2017mi²segmentcustomer
Segment Reporting Information [Line Items]
Number of Operating Segments | segment	2
Approximate number of retail customers | customer	520,000
Service area, square miles | mi²	6,000

Business Segments (Segment Fina

Business Segments (Segment Financial Information) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Segment Reporting Information [Line Items]
External customer revenues	$ 323.9	$ 364
Intersegment revenues	0	0
Total revenues	323.9	364
Depreciation and amortization	28	33.4
Fuel Costs	54.1	66.9
Depreciation and amortization	28	33.4
Impairment of Long-Lived Assets Held-for-use	66.4	0
Interest expense	26.9	26.3
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest	(83.2)	2.8
Net income / (loss) from continuing operations	(51.7)	2.2
Discontinued operations, net of tax	0	29.6
Net income/ (loss)	(51.7)	31.8
Capital expenditures	41.4	37.7
Total assets	2,264.2		$ 2,419.2
Operating Segments [Member] | Transmission and Distribution [Member]
Segment Reporting Information [Line Items]
External customer revenues	189.8	204.2
Intersegment revenues	0.3	0.3
Total revenues	190.1	204.5
Depreciation and amortization	18.1	17.2
Impairment of Long-Lived Assets Held-for-use	0
Interest expense	7.4	5.4
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest	25	34.2
Capital expenditures	26.3	24.1
Total assets	1,680.9		1,710.5
Operating Segments [Member] | Generation [Member]
Segment Reporting Information [Line Items]
External customer revenues	131.8	158.2
Intersegment revenues	0	0
Total revenues	131.8	158.2
Depreciation and amortization	7	18.6
Impairment of Long-Lived Assets Held-for-use	66.3
Interest expense	0	0.1
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest	(86.8)	(12.3)
Capital expenditures	14.1	13
Total assets	366.1		472.3
Other [Member]
Segment Reporting Information [Line Items]
External customer revenues	2.3	1.6
Intersegment revenues	1.4	1.3
Total revenues	3.7	2.9
Depreciation and amortization	2.9	(2.4)
Impairment of Long-Lived Assets Held-for-use	0.1
Interest expense	19.6	20.9
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest	(21.4)	(19.1)
Capital expenditures	1	0.6
Total assets	633.6		673.6
Adjustments and Eliminations [Member]
Segment Reporting Information [Line Items]
External customer revenues	0	0
Intersegment revenues	(1.7)	(1.6)
Total revenues	(1.7)	(1.6)
Depreciation and amortization	0	0
Impairment of Long-Lived Assets Held-for-use	0
Interest expense	(0.1)	(0.1)
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest	0	0
Capital expenditures	0	0
Total assets	(416.4)		(437.2)
Subsidiaries [Member]
Segment Reporting Information [Line Items]
External customer revenues	311.1	349.2
Intersegment revenues	0	0
Total revenues	311.1	349.2
Depreciation and amortization	23.5	34.3
Fuel Costs	50.1	62.9
Depreciation and amortization	23.5	34.3
Impairment of Long-Lived Assets Held-for-use	66.3	0
Interest expense	7.6	5.3
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest	(63.7)	46.1
Net income/ (loss)	(41.8)	33.7
Capital expenditures	34.1	35.8
Total assets	1,889.9		2,035.1
Subsidiaries [Member] | Operating Segments [Member] | Transmission and Distribution [Member]
Segment Reporting Information [Line Items]
External customer revenues	190.1	204.5
Intersegment revenues	0	0
Total revenues	190.1	204.5
Depreciation and amortization	18.1	17.2
Impairment of Long-Lived Assets Held-for-use	0
Interest expense	7.4	5.2
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest	25	34.4
Capital expenditures	26.3	24.1
Total assets	1,680.9		1,710.5
Subsidiaries [Member] | Operating Segments [Member] | Generation [Member]
Segment Reporting Information [Line Items]
External customer revenues	121	144.7
Intersegment revenues	0	0
Total revenues	121	144.7
Depreciation and amortization	5.4	17.1
Impairment of Long-Lived Assets Held-for-use	66.3
Interest expense	0.2	0.1
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest	(88.7)	11.7
Capital expenditures	7.8	11.7
Total assets	209		324.6
Subsidiaries [Member] | Adjustments and Eliminations [Member]
Segment Reporting Information [Line Items]
External customer revenues	0	0
Intersegment revenues	0	0
Total revenues	0	0
Depreciation and amortization	0	0
Impairment of Long-Lived Assets Held-for-use	0
Interest expense	0	0
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest	0	0
Capital expenditures	0	$ 0
Total assets	$ 0		$ 0

Discontinued Operations (Detail

Discontinued Operations (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2015
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Revenues		$ 0
Cost of revenues		0
Operating expenses		(0.7)
(Loss) / income from discontinued operations before income taxes	$ 0	(0.7)
Gain from disposal of discontinued operations	0	49.2
Income tax expense / (benefit) for discontinued operations	0	18.9
Discontinued operations	$ 0	29.6
Cash flows from operating activities for discontinued operations		(0.7)
Cash flows from investing activities for discontinued operations		$ 75.5
Dpler [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Deposit received on sale of DPLER			$ 75.5

Fixed-asset Impairment Fixed-as

Fixed-asset Impairment Fixed-asset Impairment (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Impairment of Long-Lived Assets Held-for-use	$ 66.4	$ 0
Stuart [Member]
Impairment of Long-Lived Assets Held-for-use	39.1
Impaired Assets to be Disposed of by Method Other than Sale, Amount of Impairment Loss	9.8
Killen [Member]
Impairment of Long-Lived Assets Held-for-use	27.3
Impaired Assets to be Disposed of by Method Other than Sale, Amount of Impairment Loss	6.4
THE DAYTON POWER AND LIGHT COMPANY [Member]
Impairment of Long-Lived Assets Held-for-use	66.3	$ 0
THE DAYTON POWER AND LIGHT COMPANY [Member] | Stuart [Member]
Impairment of Long-Lived Assets Held-for-use	39
Impaired Assets to be Disposed of by Method Other than Sale, Amount of Impairment Loss	9.8
THE DAYTON POWER AND LIGHT COMPANY [Member] | Killen [Member]
Impairment of Long-Lived Assets Held-for-use	27.3
Impaired Assets to be Disposed of by Method Other than Sale, Amount of Impairment Loss	6.4
Level 3 [Member] | Stuart [Member]
Property, Plant, and Equipment, Fair Value Disclosure	3.3
Level 3 [Member] | Killen [Member]
Property, Plant, and Equipment, Fair Value Disclosure	7.9
Level 3 [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | Stuart [Member]
Property, Plant, and Equipment, Fair Value Disclosure	3.3
Level 3 [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | Killen [Member]
Property, Plant, and Equipment, Fair Value Disclosure	$ 7.9