Schedule II Valuation And Qualifying Accounts (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Provision for Uncollectible Accounts [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	$ 835	$ 898	$ 909
Additions	4,113	3,766	4,011
Deductions	3,789	3,829	4,022
Balance at End of Period	1,159	835	898
Provision for Uncollectible Accounts [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	835	897	909
Additions	4,113	3,766	4,011
Deductions	3,789	3,828	4,023
Balance at End of Period	1,159	835	897
Valuation Allowance For Deferred Tax Assets [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	17,246	18,900	13,721
Additions	0	1,626	5,179
Deductions	13,921	3,280	0
Balance at End of Period	3,325	17,246	18,900
Assets held for sale, current [Member] | Provision for Uncollectible Accounts [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	$ 113	369	251
Additions		2,035	3,633
Deductions		2,291	3,515
Balance at End of Period		$ 113	$ 369