Equity (Narrative) (Details) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2015 USD ($) fiscal_quarter $ / shares shares	Dec. 31, 2014 USD ($) shares
Class of Stock [Line Items]
Preferred stock dividends, number of quarters in arrears to trigger permission to elect board members | fiscal_quarter	4
Maximum leverage ratio to allow distribution to shareholder	0.67
Minimum coverage ratio to allow distribution to shareholder	2.50
Amount above net income required for dividend issuance | $	$ 1.2
Retained earnings / (deficit) | $	$ (2,335.7)	$ (2,096.7)
Common stock, shares authorized	1,500	1,500
Common stock, shares outstanding	1	1
Leverage Ratio	1.03
THE DAYTON POWER AND LIGHT COMPANY [Member]
Class of Stock [Line Items]
Preferred stock dividends, number of quarters in arrears to trigger permission to elect board members | fiscal_quarter	4
Amount above net income required for dividend issuance | $	$ 1.2
Retained earnings / (deficit) | $	$ 437.3	$ 381.8
Common stock, shares authorized	250,000,000	250,000,000
Common stock, shares outstanding	41,172,173	41,172,173
PUCO Meger Equity Ratio Approval	50.00%
$100 Redeemable Preferred Stock [Member]
Class of Stock [Line Items]
Preferred stock par value | $ / shares	$ 100
Preferred stock shares authorized	4,000,000
Preferred stock shares outstanding	228,508
$100 Redeemable Preferred Stock [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Class of Stock [Line Items]
Preferred stock par value | $ / shares	$ 100
Preferred stock shares authorized	4,000,000
Preferred stock shares outstanding	228,508
$25 Redeemable Preferred Stock [Member]
Class of Stock [Line Items]
Preferred stock par value | $ / shares	$ 25
Preferred stock shares authorized	4,000,000
$25 Redeemable Preferred Stock [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Class of Stock [Line Items]
Preferred stock par value | $ / shares	$ 25
Preferred stock shares authorized	4,000,000