Investment in ATC (Details-1) (USD $)	3 Months Ended				3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Mar. 31, 2012 ATC [Member]	Dec. 31, 2011 ATC [Member]	Mar. 31, 2012 ATC [Member] Mge Transco [Member]	Mar. 31, 2011 ATC [Member] Mge Transco [Member]
Equity method investments [Line Items]
Equity earnings from investment in ATC	$ 2,242,000	$ 2,097,000			$ 2,200,000	$ 2,100,000
Dividend income from ATC	1,740,000	1,682,000			1,700,000	1,700,000
Contributions to ATC					400,000	400,000
Investment in ATC			$ 57,800,000	$ 57,000,000