Merger (Details 2) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Revenue and earnings of Allegheny
Total revenues	$ 16,258,000	[1]	$ 13,339,000	[1]	$ 12,973,000	[1]
NET INCOME	869,000		718,000		856,000
Basic Earnings Per Share	$ 2.22		$ 2.44		$ 2.87
Diluted Earnings Per Share	$ 2.21		$ 2.42		$ 2.85
Allegheny Energy Inc
Revenue and earnings of Allegheny
Total revenues	3,966,000
NET INCOME	$ 147,000
Basic Earnings Per Share	$ 0.37
Diluted Earnings Per Share	$ 0.37

[1] Includes $486 million, $428 million and $395 million of excise tax collections in 2011, 2010 and 2009, respectively.