Earnings Per Share (Schedule of Earnings Per Share, Basic and Diluted) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016		Dec. 31, 2015
Class of Stock [Line Items]
Income (loss) from continuing operations, after Adjustment to Retained Earnings, Basic Earnings									$ (507)	$ (25)	[1]	$ 318
Weighted Average Number of Shares Outstanding, Basic (in shares)									660	660		687
Income (Loss) from Continuing Operations, Per Basic Share	$ (1.03)	$ 0.22	$ 0.08	$ 0.04	$ (0.35)	$ 0.26	$ (0.15)	$ 0.21	$ (0.77)	$ (0.04)		$ 0.46
Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements (in shares)									0	0		2
Weighted Average Number of Shares Outstanding, Diluted (in shares)									660	660		689
Income (Loss) from Continuing Operations, Per Diluted Share	$ (1.03)	$ 0.22	$ 0.08	$ 0.04	$ (0.35)	$ 0.26	$ (0.15)	$ 0.20	$ (0.77)	$ (0.04)		$ 0.46
Income (loss) from continuing operations, after Adjustment to Retained Earnings, Diluted Earnings									$ (507)	$ (25)		$ 318
Temporary Equity, Accretion to Redemption Value									$ 25	$ 4
Restricted Stock Units (RSUs) [Member]
Class of Stock [Line Items]
Income (Loss) from Continuing Operations, Per Diluted Share									$ 0.00	$ 0.00		$ 0.00
Restricted Stock Units (RSUs) [Member]
Class of Stock [Line Items]
Dilutive Securities, Effect on Basic Earnings Per Share, Options and Restrictive Stock Units									$ 0	$ 0		$ 0
DPL Subsidiary [Member]
Class of Stock [Line Items]
Temporary Equity, Accretion to Redemption Value										$ 5

[1] Loss from continuing operations, net of tax, of $20 million less the $5 million adjustment to retained earnings to record the DP&L redeemable preferred stock at its redemption value as of December 31, 2016.