Rate Matters and Regulation Rate Matters and Regulation (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Jun. 30, 2015
SmartHours Program [Member]
Lost Revenue Associated with Customer Programs	$ 11.6	$ 10.1
SmartHours Program [Member] | Oklahoma Public Utility Division Staff [Member]
Lost Revenue Associated with Customer Programs		4.9
Reduction of Revenue		$ 5.2
Regional Haze [Member]
Estimated Environmental Capital Costs			$ 1,100.0