Common Equity (Common Share Activity) (Details) - shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Common Stock Oustanding [Roll Forward]
Shares outstanding, January 1 (in shares)	227,673,654	226,918,432	221,871,360
Common stock issued during the period, Shareowner Direct Plan (in shares)	640,723	732,814	606,010
Equity-based compensation plans (in shares)	5,185	22,408	112,756
Other (in shares)	(45,847)	0	(44,928)
Shares outstanding, December 31 (in shares)	231,348,646	227,673,654	226,918,432
At The Market Offering Program [Member]
Common Stock Oustanding [Roll Forward]
Common stock issued during the period, At-the-market offering programs (in shares)	3,074,931	0	4,373,234