Benefit Plans (Narrative) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014 plan	Dec. 31, 2013	Dec. 31, 2012
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan, number of plans	4
Defined contribution plan, award vesting period	5 years
Defined contribution plan contributions	$ 14	$ 15	$ 21
Defined benefit plan, number of plans disclosure	31
U.S. Non-Union Number of Defined Contribution Plans	3
Parent Company Number of Defined Contribution Plans	1
IPL Number of Non-Union Defined Contribution Plans	1
DPL Number of Non-Union Defined Contribution Plans	1
DPL Number of Union Defined Contribution Plans	1
U.S. Defined Benefit Plans
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, number of plans disclosure	5