Merger (Details 4) (USD $) In Thousands, except Per Share data	3 Months Ended				6 Months Ended				3 Months Ended	4 Months Ended
	Jun. 30, 2011		Jun. 30, 2010		Jun. 30, 2011		Jun. 30, 2010		Jun. 30, 2011 Allegheny Energy Inc	Jun. 30, 2011 Allegheny Energy Inc
Revenue and earnings of Allegheny
Total revenues	$ 4,060,000	[1]	$ 3,139,000	[1]	$ 7,636,000	[1]	$ 6,438,000	[1]	$ 1,181,000	$ 1,618,000
NET INCOME	$ 171,000		$ 256,000		$ 216,000		$ 405,000		$ 63,000	$ 17,000
Basic Earnings Per Share	$ 0.43		$ 0.87		$ 0.61		$ 1.38		$ 0.15	$ 0.04
Diluted Earnings Per Share	$ 0.43		$ 0.87		$ 0.61		$ 1.37		$ 0.15	$ 0.04

[1] *Includes excise tax collections of $116 million and $99 million in the three months ended June 30,2011 and 2010, respectively, and $235 million and $208 million in the six months ended June 30, 2011 and 2010, respectively.