Callaway Energy Center (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($) mill	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Nuclear Waste Matters [Line Items]
Litigation Settlement, Amount	$ 3	$ 24	$ 14
Nuclear Plant
Nuclear Waste Matters [Line Items]
Nwf Fee Number Of Mills | mill	1
Annual decommissioning costs included in costs of service	$ 7