Organization and Basis of Presentation (Details 4)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Annual Composite Depreciation Rate
Annual Composite Depreciation Rate (percent)	2.50%	2.50%	2.50%
FES
Annual Composite Depreciation Rate
Annual Composite Depreciation Rate (percent)	3.30%	3.20%	3.10%