Benefit Plans (Narrative) (Details) - USD ($) | 12 Months Ended |
Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019 |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined Benefit Plan, Amount Billed to Service Company | $ 1,700,000 | $ 1,400,000 | $ 1,400,000 |
Defined contribution plan, maximum annual contributions per employee (percent) | 85.00% | | |
Employer contributions to defined contribution plan | $ 3,300,000 | 3,200,000 | 3,100,000 |
Accumulated benefit obligation for our defined benefit pension plans | 400,700,000 | 436,400,000 | |
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, after Tax | 6,400,000 | (8,800,000) | (3,400,000) |
THE DAYTON POWER AND LIGHT COMPANY [Member] | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined Benefit Plan, Amount Billed to Service Company | $ 1,700,000 | 1,400,000 | 1,400,000 |
Defined contribution plan, maximum annual contributions per employee (percent) | 85.00% | | |
Employer contributions to defined contribution plan | $ 3,300,000 | 3,200,000 | 3,100,000 |
Accumulated benefit obligation for our defined benefit pension plans | 400,700,000 | 436,400,000 | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan | (8,900,000) | | |
Defined Benefit Plan, Amount Billed to AES Ohio Generation | 1,900,000 | 1,400,000 | 1,500,000 |
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, after Tax | $ 6,400,000 | (8,700,000) | $ (3,600,000) |
Defined Benefit Plan [Member] | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan employee vested percentage | 100.00% | | |
Defined benefit plan, percent forfeited if terminated, other than by death or disability, prior to full vesting (percent) | 100.00% | | |
Defined Benefit Plan [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan employee vested percentage | 100.00% | | |
Defined benefit plan, percent forfeited if terminated, other than by death or disability, prior to full vesting (percent) | 100.00% | | |
Management Employees [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan employee vested percentage | 100.00% | | |
Defined benefit plan, percent forfeited if terminated, other than by death or disability, prior to full vesting (percent) | 100.00% | | |
Cash Balance Plan [Member] | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined benefit plan employee vested percentage | 100.00% | | |
Defined benefit plan, percent forfeited if terminated, other than by death or disability, prior to full vesting (percent) | 100.00% | | |
Pension [Member] | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss) | $ (12,700,000) | $ 52,700,000 | |
Payment for Pension Benefits | $ 9,800,000 | | |
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets | 4.55% | 5.60% | 6.25% |
Discount rate for obligations | 2.83% | 2.44% | 3.33% |
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate | 2.44% | 3.33% | 4.35% |
Defined Benefit Plan, Plan Assets, Amount | $ 363,500,000 | $ 365,100,000 | $ 352,000,000 |
Service cost | 4,500,000 | 3,700,000 | 3,700,000 |
Interest cost | 8,200,000 | 11,800,000 | 14,900,000 |
Defined Benefit Plan, Funded (Unfunded) Status of Plan | $ (52,700,000) | (84,400,000) | |
Defined benefit plan, amortization period for underfunding excess | 7 years | | |
Pension [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss) | $ (12,700,000) | 52,700,000 | |
Payment for Pension Benefits | $ 9,800,000 | $ 7,500,000 | $ 7,500,000 |
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets | 4.55% | 5.60% | 6.25% |
Discount rate for obligations | 2.83% | 2.44% | 3.33% |
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate | 2.44% | 3.33% | 4.35% |
Defined Benefit Plan, Plan Assets, Amount | $ 363,500,000 | $ 365,100,000 | $ 352,000,000 |
Service cost | 4,500,000 | 3,700,000 | 3,700,000 |
Interest cost | 8,200,000 | 11,800,000 | $ 14,900,000 |
Defined Benefit Plan, Funded (Unfunded) Status of Plan | $ (52,700,000) | (84,400,000) | |
Defined benefit plan, amortization period for underfunding excess | 7 years | | |
Postretirement [Member] | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan | | 9,000,000 | |
Postretirement [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan | $ 8,900,000 | $ 9,000,000 | |
SERP [Member] | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined Benefit Plan, Target Allocation Percentage | 114.00% | | |
Equity Securities [Member] | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage | 41.00% | | |
Equity Securities [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage | 41.00% | | |
Forecast [Member] | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets | 4.60% | | |
Increase in pension cost due to change in return on assets | $ 3,400,000 | | |
Decrease in pension cost due to change in return on assets | (3,400,000) | | |
Decrease in pension cost due to change in discount rate | (500,000) | | |
Increase in pension cost due to change in discount rate | $ 500,000 | | |
Forecast [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets | 4.60% | | |
Increase in pension cost due to change in return on assets | $ 3,400,000 | | |
Decrease in pension cost due to change in return on assets | (3,400,000) | | |
Decrease in pension cost due to change in discount rate | (500,000) | | |
Increase in pension cost due to change in discount rate | 500,000 | | |
Forecast [Member] | Pension [Member] | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Payment for Pension Benefits | 7,500,000 | | |
Service cost | 5,800,000 | | |
Defined Benefit Plan, Plan Assets, Administration Expense | 1,700,000 | | |
Forecast [Member] | Pension [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Payment for Pension Benefits | 7,500,000 | | |
Service cost | 5,800,000 | | |
Defined Benefit Plan, Plan Assets, Administration Expense | 1,700,000 | | |
Forecast [Member] | SERP [Member] | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Estimated contribution to the defined benefit plans next year | $ 200,000 | | |
Forecast [Member] | SERP [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined Benefit Plan, Target Allocation Percentage | 114.00% | | |
Estimated contribution to the defined benefit plans next year | $ 200,000 | | |
Increase in Expected Rate of Return [Member] | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Change in Expected rate of return on plan assets | 1.00% | | |
Increase in Expected Rate of Return [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Change in Expected rate of return on plan assets | 1.00% | | |
Decrease in Expected Rate of Return [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Change in Expected rate of return on plan assets | 1.00% | | |
Expected Increase in Discount Rate [Member] | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Change in discount rate for plan assets | 25.00% | | |
Expected Increase in Discount Rate [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Change in discount rate for plan assets | 25.00% | | |
Expected Decrease in Discount Rate [Member] | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Change in discount rate for plan assets | 25.00% | | |
Expected Decrease in Discount Rate [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Change in discount rate for plan assets | 25.00% | | |
Non-union Participant [Member] | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined contribution plan, period after which participant is fully vested in employer contributions | 2 years | | |
Non-union Participant [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined contribution plan, period after which participant is fully vested in employer contributions | 2 years | | |
Non-union Participant [Member] | First 1% of Eligible Compensation [Member] | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined contribution plan, employer matching contribution (percent) | 100.00% | | |
Defined contribution plan, employer matching contribution, percent of employees' gross pay (percent) | 1.00% | | |
Non-union Participant [Member] | First 1% of Eligible Compensation [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined contribution plan, employer matching contribution (percent) | 100.00% | | |
Defined contribution plan, employer matching contribution, percent of employees' gross pay (percent) | 1.00% | | |
Non-union Participant [Member] | Next 5% of Eligible Compensation [Member] | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined contribution plan, employer matching contribution (percent) | 50.00% | | |
Defined contribution plan, employer matching contribution, percent of employees' gross pay (percent) | 5.00% | | |
Non-union Participant [Member] | Next 5% of Eligible Compensation [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined contribution plan, employer matching contribution (percent) | 50.00% | | |
Defined contribution plan, employer matching contribution, percent of employees' gross pay (percent) | 5.00% | | |
Union Participant [Member] | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined contribution plan, employer matching contribution, percent of employees' gross pay (percent) | 150.00% | | |
Defined contribution plan, period after which participant is fully vested in employer contributions | 3 years | | |
Defined contribution plan, employer matching contribution cap | $ 2,650 | | |
Union Participant [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined contribution plan, employer matching contribution, percent of employees' gross pay (percent) | 150.00% | | |
Defined contribution plan, period after which participant is fully vested in employer contributions | 3 years | | |
Defined contribution plan, employer matching contribution cap | $ 2,650 | | |
Minimum [Member] | Equity Securities [Member] | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage | 40.00% | | |
Minimum [Member] | Equity Securities [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage | 40.00% | | |
Minimum [Member] | Fixed Income Securities [Member] | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage | 50.00% | | |
Minimum [Member] | Fixed Income Securities [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage | 50.00% | | |
Maximum [Member] | Equity Securities [Member] | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage | 50.00% | | |
Maximum [Member] | Equity Securities [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage | 50.00% | | |
Maximum [Member] | Fixed Income Securities [Member] | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage | 60.00% | | |
Maximum [Member] | Fixed Income Securities [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage | 60.00% | | |