Consolidated Statements of Capitalization - Capital Stock (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Preferred stock - par value	$ 100
Preferred stock, no par value
Equity contributions made by TECO Energy	$ 345	$ 190
Preferred Stock Par Value [Member]
Preferred stock, shares authorized	1,500,000
Preferred stock, shares outstanding	0
Preferred Stock No Par Value [Member]
Preferred stock, shares authorized	2,500,000
Preferred stock, shares outstanding	0
Preference Stock No Par Value
Preferred stock, shares authorized	2,500,000
Preferred stock, shares outstanding	0