Consolidated Balance Sheets (Parenthetical) (USD $) In Millions, except Per Share data, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Receivables, less allowance for uncollectibles	$ 4.2	$ 2.6
Common equity, shares authorized	400.0	400.0
Common equity, par value	$ 1	$ 1
Common equity, shares outstanding	216.6	215.8
TAMPA ELECTRIC CO [Member]
Receivables, less allowance for uncollectibles	$ 1.5	$ 1.3
Common equity, shares authorized	25.0	25.0
Common equity, shares outstanding	10.0	10.0