Consolidated Statements of Capitalization - Capital Stock (Detail) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2012	Dec. 31, 2011
Common equity, shares authorized	400.0	400.0	400.0	400.0
Capital Stock Outstanding December 31, Shares	216.6	215.8	216.6	215.8
Cash Dividends Paid Per Share	$ 0.220	$ 0.215	$ 0.880	$ 0.850
Cash Dividends Paid			$ 190.4	$ 183.2
TAMPA ELECTRIC CO [Member]
Common equity, shares authorized	25.0	25.0	25.0	25.0
Current Redemption on Price
Capital Stock Outstanding December 31, Shares	10.0	10.0	10.0	10.0
Capital Stock Outstanding December 31, Amount	1,970.4	1,852.4	1,970.4	1,852.4
Cash Dividends Paid Per Share
Cash Dividends Paid			$ 228.3	$ 240.7

Common Stock Current Redemption On Price.

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Cash outflow in the form of capital distributions and dividends to common shareholders, preferred shareholders and noncontrolling interests.

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