Benefit Plans (Tables)

12 Months Ended

Dec. 31, 2016

Pension And Postretirement Benefit Plans' Obligations And Assets

The following tables set forth the changes in our pension plan's obligations and assets recorded on the balance sheets at December 31, 2016 and 2015. The amounts presented in the following tables for pension obligations include the collective bargaining plan formula, traditional management plan formula and cash balance plan formula and the SERP in the aggregate and have not been adjusted for $1.3 million and $2.2 million of costs billed to the service company for the years ended December 31, 2016 and 2015.

$ in millions	Pension
	Years ended December 31,
	2016			2015
Change in benefit obligation
Benefit obligation at January 1	$	410.8		$	443.8
Service cost	5.7			7.1
Interest cost	14.7			17.3
Plan curtailment	2.5			—
Actuarial (gain) / loss	9.0			(34.5		)
Benefits paid	(23.1		)	(22.9		)
Benefit obligation at December 31	419.6			410.8
Change in plan assets
Fair value of plan assets at January 1	345.4			371.7
Actual return on plan assets	13.3			(8.8		)
Employer contributions	5.4			5.4
Benefits paid	(23.1		)	(22.9		)
Fair value of plan assets at December 31	341.0			345.4
Unfunded status of plan	$	(78.6	)	$	(65.4	)
	December 31,
Amounts recognized in the Balance sheets	2016			2015
Current liabilities	$	(0.4	)	$	(0.4	)
Non-current liabilities	(78.2		)	(65.0		)
Net liability at December 31,	$	(78.6	)	$	(65.4	)
Amounts recognized in Accumulated Other Comprehensive Income, Regulatory Assets and Regulatory Liabilities, pre-tax
Components:
Prior service cost	$	8.8		$	12.0
Net actuarial loss	108.9			94.7
Accumulated Other Comprehensive Income, Regulatory Assets and Regulatory Liabilities, pre-tax	$	117.7		$	106.7
Recorded as:
Regulatory asset	$	97.1		$	91.1
Accumulated other comprehensive income	20.6			15.6
Accumulated Other Comprehensive Income, Regulatory Assets and Regulatory Liabilities, pre-tax	$	117.7		$	106.7

Schedule of Amounts Recognized in Balance Sheet

The following tables set forth the changes in our pension plan's obligations and assets recorded on the balance sheets at December 31, 2016 and 2015. The amounts presented in the following tables for pension obligations include the collective bargaining plan formula, traditional management plan formula and cash balance plan formula and the SERP in the aggregate and have not been adjusted for $1.3 million and $2.2 million of costs billed to the service company for the years ended December 31, 2016 and 2015.

$ in millions	Pension
	Years ended December 31,
	2016			2015
Change in benefit obligation
Benefit obligation at January 1	$	410.8		$	443.8
Service cost	5.7			7.1
Interest cost	14.7			17.3
Plan curtailment	2.5			—
Actuarial (gain) / loss	9.0			(34.5		)
Benefits paid	(23.1		)	(22.9		)
Benefit obligation at December 31	419.6			410.8
Change in plan assets
Fair value of plan assets at January 1	345.4			371.7
Actual return on plan assets	13.3			(8.8		)
Employer contributions	5.4			5.4
Benefits paid	(23.1		)	(22.9		)
Fair value of plan assets at December 31	341.0			345.4
Unfunded status of plan	$	(78.6	)	$	(65.4	)
	December 31,
Amounts recognized in the Balance sheets	2016			2015
Current liabilities	$	(0.4	)	$	(0.4	)
Non-current liabilities	(78.2		)	(65.0		)
Net liability at December 31,	$	(78.6	)	$	(65.4	)
Amounts recognized in Accumulated Other Comprehensive Income, Regulatory Assets and Regulatory Liabilities, pre-tax
Components:
Prior service cost	$	8.8		$	12.0
Net actuarial loss	108.9			94.7
Accumulated Other Comprehensive Income, Regulatory Assets and Regulatory Liabilities, pre-tax	$	117.7		$	106.7
Recorded as:
Regulatory asset	$	97.1		$	91.1
Accumulated other comprehensive income	20.6			15.6
Accumulated Other Comprehensive Income, Regulatory Assets and Regulatory Liabilities, pre-tax	$	117.7		$	106.7

Schedule of Net Periodic Benefit Cost / (Income)

Net Periodic Benefit Cost
	Years ended December 31,
$ in millions	2016			2015			2014
Service cost	$	5.7		$	7.1		$	5.9
Interest cost	14.7			17.3			17.5
Expected return on assets	(22.8		)	(22.6		)	(22.9		)
Plan curtailment	3.8			—			—
Amortization of unrecognized:
Actuarial loss	4.3			5.8			3.4
Prior service cost	1.8			2.0			1.5
Net periodic benefit cost	$	7.5		$	9.6		$	5.4
Rates relevant to each year's expense calculations
Discount rate	4.49		%	4.02		%	4.86		%
Expected return on plan assets	6.50		%	6.50		%	6.75		%

Other Changes in Plan Assets and Benefit Obligation Recognized in Accumulated Other Comprehensive Income, Regulatory Assets and Regulatory Liabilities

Other Changes in Plan Assets and Benefit Obligation Recognized in Accumulated Other Comprehensive Income, Regulatory Assets And Regulatory Liabilities

Other Changes in Plan Assets and Benefit Obligation Recognized in Accumulated Other Comprehensive Income, Regulatory Assets and Regulatory Liabilities

	Years ended December 31,
$ in millions	2016			2015			2014
Net actuarial loss / (gain)	$	20.9		$	(3.0	)	$	43.8
Prior service cost	—			—			6.8
Plan curtailment	(3.8		)	—			—
Reversal of amortization item:
Net actuarial loss	(4.3		)	(5.8		)	(3.4		)
Prior service cost	(1.8		)	(2.0		)	(1.5		)
Total recognized in Accumulated Other Comprehensive Income, Regulatory Assets and Regulatory Liabilities	$	11.0		$	(10.8	)	$	45.7
Total recognized in net periodic benefit cost and Accumulated Other Comprehensive Income, Regulatory Assets and Regulatory Liabilities	$	18.5		$	(1.2	)	$	51.1

Estimated Amounts that will be Amortized from Accumulated Other Comprehensive Income, Regulatory Assets And Regulatory Liabilities

Estimated amounts that will be amortized from AOCI, Regulatory assets and Regulatory liabilities into net periodic benefit costs during 2017 are:

$ in millions	Pension
Actuarial loss	$	5.8
Prior service cost	$	1.4

Weighted Average Assumptions Used to Determine Benefit Obligations

The weighted average assumptions used to determine benefit obligations at December 31, 2016, 2015 and 2014 were:

Benefit Obligation Assumptions	Pension
	2016	2015	2014
Discount rate for obligations	4.28%	4.49%	4.02%
Rate of compensation increases	3.94%	3.94%	3.94%

Schedule of Allocation of Plan Assets

The following table summarizes our target pension plan allocation for 2016:

	Long-Term Mid-Point Target Allocation	Percentage of plan assets as of December 31,
Asset category		2016	2015
Equity Securities	38%	37%	17%
Debt Securities	56%	53%	67%
Real Estate	6%	10%	9%
Other	—%	—%	7%

Estimated Future Benefit Payments and Medicare Part D Reimbursements

Estimated future benefit payments
$ in millions due within the following years:	Pension
2017	$	25.0
2018	$	25.5
2019	$	26.0
2020	$	26.4
2021	$	26.7
2022 - 2026	$	139.6

THE DAYTON POWER AND LIGHT COMPANY [Member]

Schedule of Amounts Recognized in Balance Sheet

December 31, 2016 and 2015. The amounts presented in the following tables for pension obligations include the collective bargaining plan formula, traditional management plan formula and cash balance plan formula and the SERP in the aggregate and have not been adjusted for $1.3 million and $2.2 million of costs billed to the service company for the years ended December 31, 2016 and 2015.

$ in millions	Pension
	Years ended December 31,
	2016			2015
Change in benefit obligation
Benefit obligation at January 1	$	410.8		$	443.8
Service cost	5.7			7.1
Interest cost	14.7			17.3
Plan curtailment	2.5			—
Actuarial (gain) / loss	9.0			(34.5		)
Benefits paid	(23.1		)	(22.9		)
Benefit obligation at December 31	419.6			410.8
Change in plan assets
Fair value of plan assets at January 1	345.4			371.7
Actual return on plan assets	13.3			(8.8		)
Employer contributions	5.4			5.4
Benefits paid	(23.1		)	(22.9		)
Fair value of plan assets at December 31	341.0			345.4
Funded status of plan	$	(78.6	)	$	(65.4	)
	December 31,
Amounts recognized in the Balance sheets	2016			2015
Current liabilities	$	(0.4	)	$	(0.4	)
Non-current liabilities	(78.2		)	(65.0		)
Net liability	$	(78.6	)	$	(65.4	)
Amounts recognized in Accumulated Other Comprehensive Income, Regulatory Assets and Regulatory Liabilities, pre-tax
Components:
Prior service cost	$	10.8		$	17.0
Net actuarial loss	150.9			139.7
Accumulated Other Comprehensive Income, Regulatory Assets and Regulatory Liabilities, pre-tax	$	161.7		$	156.7
Recorded as:
Regulatory asset	$	97.1		$	91.1
Accumulated other comprehensive income	64.6			65.6
Accumulated Other Comprehensive Income, Regulatory Assets and Regulatory Liabilities, pre-tax	$	161.7		$	156.7

Schedule of Net Periodic Benefit Cost / (Income)

Net Periodic Benefit Cost
	Years ended December 31,
$ in millions	2016			2015			2014
Service cost	$	5.7		$	7.1		$	5.9
Interest cost	14.7			17.3			17.5
Expected return on assets	(22.8		)	(22.6		)	(22.9		)
Plan curtailment	5.7			—			—
Amortization of unrecognized:
Actuarial loss	7.2			9.8			6.4
Prior service cost	3.0			3.3			2.8
Net periodic benefit cost	$	13.5		$	14.9		$	9.7
Rates relevant to each year's expense calculations
Discount rate	4.49		%	4.02		%	4.86		%
Expected return on plan assets	6.50		%	6.50		%	6.75		%

Estimated Amounts that will be Amortized from Accumulated Other Comprehensive Income, Regulatory Assets And Regulatory Liabilities

Estimated amounts that will be amortized from AOCI, Regulatory assets and Regulatory liabilities into net periodic benefit costs during 2017 are:

$ in millions	Pension
Actuarial loss	$	9.7
Prior service cost	$	1.9

Weighted Average Assumptions Used to Determine Benefit Obligations

The weighted average assumptions used to determine benefit obligations at December 31, 2016, 2015 and 2014 were:

Benefit Obligation Assumptions	Pension
	2016	2015	2014
Discount rate for obligations	4.28%	4.49%	4.02%
Rate of compensation increases	3.94%	3.94%	3.94%

Weighted Average Assumptions Used to Determine Net Periodic Benefit Cost (Income)

Assumed Health Care Cost Trend Rates

Effect of Change in Health Care Cost Trend Rate

Schedule of Allocation of Plan Assets

The following table summarizes our target pension plan allocation for 2016:

	Long-Term Mid-Point Target Allocation	Percentage of plan assets as of December 31,
Asset Category		2016	2015
Equity Securities	38%	37%	17%
Debt Securities	56%	53%	67%
Real Estate	6%	10%	9%
Other	—%	—%	7%

Fair Value Measurements for Plan Assets

The fair values of our pension plan assets at December 31, 2016 by asset category are as follows:

Fair Value Measurements for Pension Plan Assets at December 31, 2016
Asset Category $ in millions	Market Value at December 31, 2016		Quoted prices in active markets for identical assets		Significant observable inputs		Significant unobservable inputs
			(Level 1)		(Level 2)		(Level 3)
Mutual funds:
U.S. equities (a)	$	81.4	$	81.4	$	—	$	—
International equities (a)	44.4		44.4		—		—
Fixed income (b)	151.1		151.1		—		—
Fixed income securities
U.S. Treasury securities	31.0		31.0		—		—
Other investments:
Core property collective fund (c)	33.1		—		33.1		—
Total pension plan assets	$	341.0	$	307.9	$	33.1	$	—

(a) This category includes investments in equity securities of large, small and medium sized U.S. companies and equity securities of foreign companies including those in developing countries. The funds are valued using the net asset value method in which an average of the market prices for the underlying investments is used to value the fund.

(b) This category includes investments in investment-grade fixed-income instruments, U.S. dollar-denominated debt securities of emerging market issuers and high yield fixed-income securities that are rated below investment grade. The funds are valued using the net asset value method in which an average of the market prices for the underlying investments is used to value the fund.

(c) This category represents a property fund that invests in commercial real estate. The fair value of the fund is valued using the net asset value method in which an average of the market prices for the underlying investments is used to value the fund.

The fair values of our pension plan assets at December 31, 2015 by asset category are as follows:

Fair Value Measurements for Pension Plan Assets at December 31, 2015
Asset Category $ in millions	Market Value at December 31, 2015		Quoted prices in active markets for identical assets		Significant observable inputs		Significant unobservable inputs
			(Level 1)		(Level 2)		(Level 3)
Mutual funds:
U.S. equities (a)	$	39.4	$	39.4	$	—	$	—
International equities (a)	20.9		20.9		—		—
Fixed income (b)	232.1		232.1		—		—
Other investments:(c)
Core property collective fund	30.2		—		30.2		—
Common collective fund	22.8		—		22.8		—
Total pension plan assets	$	345.4	$	292.4	$	53.0	$	—

(a) This category includes investments in equity securities of large, small and medium sized U.S. companies and equity securities of foreign companies including those in developing countries. The funds are valued using the net asset value method in which an average of the market prices for the underlying investments is used to value the fund.

(b) This category includes investments in investment-grade fixed-income instruments, U.S. dollar-denominated debt securities of emerging market issuers and high yield fixed-income securities that are rated below investment grade. The funds are valued using the net asset value method in which an average of the market prices for the underlying investments is used to value the fund.

(c) This category represents a property fund that invests in commercial real estate and a hedge fund of funds made up of 30+ different hedge fund managers diversified over eight different hedge strategies. The fair value of the hedge fund is valued using the net asset value method in which an average of the market prices for the underlying investments is used to value the fund.

Estimated Future Benefit Payments and Medicare Part D Reimbursements

Estimated future benefit payments
$ in millions due within the following years:	Pension
2017	$	25.0
2018	$	25.5
2019	$	26.0
2020	$	26.4
2021	$	26.7
2022 - 2026	$	139.6

Pension [Member]

Fair Value Measurements for Plan Assets

The fair values of our pension plan assets at December 31, 2016 by asset category are as follows:

Fair Value Measurements for Pension Plan Assets at December 31, 2016
Asset Category $ in millions	Market Value at December 31, 2016		Quoted prices in active markets for identical assets		Significant observable inputs		Significant unobservable inputs
			(Level 1)		(Level 2)		(Level 3)
Mutual funds:
U.S. equities (a)	$	81.4	$	81.4	$	—	$	—
International equities (a)	44.4		44.4		—		—
Fixed income (b)	151.1		151.1		—		—
Fixed income securities:
U.S. Treasury securities	31.0		31.0		—		—
Other investments:
Core property collective fund (c)	33.1		—		33.1		—
Total pension plan assets	$	341.0	$	307.9	$	33.1	$	—

(a) This category includes investments in equity securities of large, small and medium sized U.S. companies and equity securities of foreign companies including those in developing countries. The funds are valued using the net asset value method in which an average of the market prices for the underlying investments is used to value the fund.

(b) This category includes investments in investment-grade fixed-income instruments, U.S. dollar-denominated debt securities of emerging market issuers and high yield fixed-income securities that are rated below investment grade. The funds are valued using the net asset value method in which an average of the market prices for the underlying investments is used to value the fund.

(c) This category represents a property fund that invests in commercial real estate. The fair value of the fund is valued using the net asset value method in which an average of the market prices for the underlying investments is used to value the fund.

The fair values of our pension plan assets at December 31, 2015 by asset category are as follows:

Fair Value Measurements for Pension Plan Assets at December 31, 2015
Asset Category $ in millions	Market Value at December 31, 2015		Quoted prices in active markets for identical assets		Significant observable inputs		Significant unobservable inputs
			(Level 1)		(Level 2)		(Level 3)
Mutual funds:
U.S. equities (a)	$	39.4	$	39.4	$	—	$	—
International equities (a)	20.9		20.9		—		—
Fixed income (b)	232.1		232.1		—		—
Other investments:(c)
Core property collective fund	30.2		—		30.2		—
Common collective fund	22.8		—		22.8		—
Total pension plan assets	$	345.4	$	292.4	$	53.0	$	—

(a) This category includes investments in equity securities of large, small and medium sized U.S. companies and equity securities of foreign companies including those in developing countries. The funds are valued using the net asset value method in which an average of the market prices for the underlying investments is used to value the fund.

(b) This category includes investments in investment-grade fixed-income instruments, U.S. dollar-denominated debt securities of emerging market issuers and high yield fixed-income securities that are rated below investment grade. The funds are valued using the net asset value method in which an average of the market prices for the underlying investments is used to value the fund.

(c) This category represents a property fund that invests in commercial real estate and a hedge fund of funds made up of 30+ different hedge fund managers diversified over eight different hedge strategies. The fair value of the hedge fund is valued using the net asset value method in which an average of the market prices for the underlying investments is used to value the fund.

Pension [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]

Pension And Postretirement Benefit Plans' Obligations And Assets

$ in millions	Pension
	Years ended December 31,
	2016			2015
Change in benefit obligation
Benefit obligation at January 1	$	410.8		$	443.8
Service cost	5.7			7.1
Interest cost	14.7			17.3
Plan curtailment	2.5			—
Actuarial (gain) / loss	9.0			(34.5		)
Benefits paid	(23.1		)	(22.9		)
Benefit obligation at December 31	419.6			410.8
Change in plan assets
Fair value of plan assets at January 1	345.4			371.7
Actual return on plan assets	13.3			(8.8		)
Employer contributions	5.4			5.4
Benefits paid	(23.1		)	(22.9		)
Fair value of plan assets at December 31	341.0			345.4
Funded status of plan	$	(78.6	)	$	(65.4	)
	December 31,
Amounts recognized in the Balance sheets	2016			2015
Current liabilities	$	(0.4	)	$	(0.4	)
Non-current liabilities	(78.2		)	(65.0		)
Net liability	$	(78.6	)	$	(65.4	)
Amounts recognized in Accumulated Other Comprehensive Income, Regulatory Assets and Regulatory Liabilities, pre-tax
Components:
Prior service cost	$	10.8		$	17.0
Net actuarial loss	150.9			139.7
Accumulated Other Comprehensive Income, Regulatory Assets and Regulatory Liabilities, pre-tax	$	161.7		$	156.7
Recorded as:
Regulatory asset	$	97.1		$	91.1
Accumulated other comprehensive income	64.6			65.6
Accumulated Other Comprehensive Income, Regulatory Assets and Regulatory Liabilities, pre-tax	$	161.7		$	156.7

Other Changes in Plan Assets and Benefit Obligation Recognized in Accumulated Other Comprehensive Income, Regulatory Assets And Regulatory Liabilities

Other Changes in Plan Assets and Benefit Obligation Recognized in Accumulated Other Comprehensive Income, Regulatory Assets and Regulatory Liabilities

	Years ended December 31,
$ in millions	2016			2015			2014
Net actuarial loss / (gain)	$	20.9		$	(3.0	)	$	43.8
Prior service cost	—			—			6.8
Plan curtailment	(5.7		)	—			—
Reversal of amortization item:
Net actuarial loss	(7.2		)	(9.8		)	(6.4		)
Prior service cost	(3.0		)	(3.3		)	(2.8		)
Total recognized in Accumulated Other Comprehensive Income, Regulatory Assets and Regulatory Liabilities	$	5.0		$	(16.1	)	$	41.4
Total recognized in net periodic benefit cost and Accumulated Other Comprehensive Income, Regulatory Assets and Regulatory Liabilities	$	18.5		$	(1.2	)	$	51.1

Postretirement [Member]

Fair Value Measurements for Plan Assets

Pension funding

Postretirement [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]

Pension And Postretirement Benefit Plans' Obligations And Assets

Fair Value Measurements for Plan Assets