Callaway Energy Center (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014 mill	Dec. 31, 2013	Dec. 31, 2012
Loss Contingencies [Line Items]
Nwf Fee Number Of Mills	1
Annual decommissioning costs included in costs of service		$ 7	$ 7
Nuclear Plant
Loss Contingencies [Line Items]
Useful life	40 years
Annual decommissioning costs included in costs of service	7