Consolidated Statements of Capitalization - Capital Stock (Detail) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2015	Dec. 31, 2014
Common equity, shares authorized	400,000,000	400,000,000	400,000,000	400,000,000
Capital Stock Outstanding December 31, Shares	235,300,000	234,900,000	235,300,000	234,900,000
Cash Dividends Paid Per Share	$ 0.225	$ 0.220	$ 0.90	$ 0.88
Cash Dividends Paid			$ 211.7	$ 199.2
Tampa Electric Company [Member]
Common equity, shares authorized	25,000,000	25,000,000	25,000,000	25,000,000
Capital Stock Outstanding December 31, Shares	10	10	10	10
Capital Stock Outstanding December 31, Amount	$ 2,305.4	$ 2,130.4	$ 2,305.4	$ 2,130.4
Cash Dividends Paid			$ 268.4	$ 262.6