Merger (Details 4) (USD $) In Thousands, except Per Share data	3 Months Ended				9 Months Ended				3 Months Ended		7 Months Ended
	Sep. 30, 2011		Sep. 30, 2010		Sep. 30, 2011		Sep. 30, 2010		Sep. 30, 2011 Allegheny Energy Inc		Sep. 30, 2011 Allegheny Energy Inc
Revenue and earnings of Allegheny
Total revenues	$ 4,719,000	[1]	$ 3,728,000	[1]	$ 12,355,000	[1]	$ 10,168,000	[1]	$ 1,273,000		$ 2,891,000
NET INCOME	$ 509,000		$ 175,000		$ 725,000		$ 580,000		$ 130,000	[2]	$ 147,000	[2]
Basic Earnings Per Share	$ 1.22		$ 0.59		$ 1.89		$ 1.97		$ 0.31		$ 0.37
Diluted Earnings Per Share	$ 1.22		$ 0.59		$ 1.88		$ 1.96		$ 0.31		$ 0.37

[1] Includes excise tax collections of $137 million and $120 million in the three months ended September 30, 2011 and 2010, respectively, and $371 million and $328 million in the nine months ended September 30, 2011 and 2010, respectively.

[2] Includes Allegheny’s after-tax merger costs of $1 million and $57 million, respectively.