Callaway Energy Center (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended							12 Months Ended
	Dec. 31, 2013 mill	Dec. 31, 2012	Dec. 31, 2011	Jun. 30, 2011	Dec. 31, 2011 Reduction To Depreciation And Amortization	Dec. 31, 2011 Reduction To Other Operations And Maintenance	Dec. 31, 2012 Reduction In Property And Plant	Dec. 31, 2013 Nuclear Plant	Mar. 30, 2014 Nuclear Plant
Loss Contingencies [Line Items]
Nwf Fee Number Of Mills	1
Settlement payment				$ 11	$ 2	$ 2	$ 1	$ 6
Gain Contingency, Unrecorded Amount									15
Useful life								40 years
Annual decommissioning costs included in costs of service		$ 7	$ 7					$ 7
MoPSC requirement to file updated cost study and funding analysis for decommissioning Callaway energy center	3 years