Common Equity Automatic Dividend Reinvestment and Stock Purchase Plan (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2015	Jun. 30, 2014
Proceeds From Issuance of Shares Under Dividend Reinvestment Plan And Stock Purchase Plan		$ 6.8	$ 6.7
Automatic Dividend Reinvestment and Stock Purchase Plan [Member]
Stock Issued During Period, Shares, Dividend Reinvestment Plan and Stock Purchase Plan	111,004	200,872
Proceeds From Issuance of Shares Under Dividend Reinvestment Plan And Stock Purchase Plan	$ 3.5	$ 6.8
Shares Held in Reserve Related to Dividend Reinvestment Plan and Stock Purchase Plan	4,790,940	4,790,940