Fair Value (Nonrecurring Unobservable Inputs) (Details) - USD ($)		6 Months Ended	12 Months Ended
		Jun. 30, 2016	Dec. 31, 2016	Aug. 31, 2016	Mar. 31, 2016
Buffalo Gap
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Assets, Fair Value Disclosure, Nonrecurring			$ 36,000,000
buffalo gap II [Member] [Member]
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Assets, Fair Value Disclosure, Nonrecurring					$ 92,000,000
Fair Value | Level 3
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Assets, Fair Value Disclosure, Nonrecurring			320,000,000
Long Lived Assets Held And Used [Member] | Fair Value | Level 3 | Buffalo Gap
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Assets, Fair Value Disclosure, Nonrecurring	[1]			$ 36,000,000
Long Lived Assets Held And Used [Member] | Fair Value | Level 3 | DPL Subsidiary
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Assets, Fair Value Disclosure, Nonrecurring	[1],[2]	$ 89,000,000	$ 103,000,000
Long Lived Assets Held And Used [Member] | Fair Value | Level 3 | buffalo gap II [Member] [Member]
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Assets, Fair Value Disclosure, Nonrecurring	[1]				$ 92,000,000
Income Approach Valuation Technique [Member] | Long Lived Assets Held And Used [Member] | Minimum | Buffalo Gap
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Fair Value Inputs, Long-term Revenue Growth Rate			(20.00%)
Fair Value Inputs, Long-term Pre-tax Operating Margin, Percent			(40.00%)
Income Approach Valuation Technique [Member] | Long Lived Assets Held And Used [Member] | Minimum | DPL Subsidiary
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Fair Value Inputs, Long-term Revenue Growth Rate		(11.00%)	(13.00%)
Fair Value Inputs, Long-term Pre-tax Operating Margin, Percent		(50.00%)	(42.00%)
Fair Value Inputs, Discount Rate		7.00%	7.00%
Income Approach Valuation Technique [Member] | Long Lived Assets Held And Used [Member] | Minimum | buffalo gap II [Member] [Member]
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Fair Value Inputs, Long-term Revenue Growth Rate			(17.00%)
Fair Value Inputs, Long-term Pre-tax Operating Margin, Percent			(166.00%)
Income Approach Valuation Technique [Member] | Long Lived Assets Held And Used [Member] | Maximum | Buffalo Gap
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Fair Value Inputs, Long-term Revenue Growth Rate			9.00%
Fair Value Inputs, Long-term Pre-tax Operating Margin, Percent			42.00%
Income Approach Valuation Technique [Member] | Long Lived Assets Held And Used [Member] | Maximum | DPL Subsidiary
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Fair Value Inputs, Long-term Revenue Growth Rate		13.00%	(1.00%)
Fair Value Inputs, Long-term Pre-tax Operating Margin, Percent		60.00%	3.00%
Fair Value Inputs, Discount Rate		12.00%	10.00%
Income Approach Valuation Technique [Member] | Long Lived Assets Held And Used [Member] | Maximum | buffalo gap II [Member] [Member]
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Fair Value Inputs, Long-term Revenue Growth Rate			21.00%
Fair Value Inputs, Long-term Pre-tax Operating Margin, Percent			48.00%
Income Approach Valuation Technique [Member] | Long Lived Assets Held And Used [Member] | Weighted Average | Buffalo Gap
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Fair Value Inputs, Long-term Revenue Growth Rate			(14.00%)
Fair Value Inputs, Long-term Pre-tax Operating Margin, Percent			29.00%
Fair Value Inputs, Discount Rate			9.00%
Income Approach Valuation Technique [Member] | Long Lived Assets Held And Used [Member] | Weighted Average | DPL Subsidiary
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Fair Value Inputs, Long-term Revenue Growth Rate		1.00%	(6.00%)
Fair Value Inputs, Long-term Pre-tax Operating Margin, Percent		5.00%	(16.00%)
Income Approach Valuation Technique [Member] | Long Lived Assets Held And Used [Member] | Weighted Average | buffalo gap II [Member] [Member]
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Fair Value Inputs, Long-term Revenue Growth Rate			20.00%
Fair Value Inputs, Long-term Pre-tax Operating Margin, Percent			18.00%
Fair Value Inputs, Discount Rate			9.00%

[1] See Note 20—Asset Impairment Expense for further information.

[2] See Note 20—Asset Impairment Expense for further discussion of each DPL impairment.