Consolidated Statements of Capitalization - Long-Term Debt (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2011 TAMPA ELECTRIC CO [Member] 1.5% term rate bonds repurchased in 2011 [Member]	Dec. 31, 2012 PGS [Member] Long-Term Debt [Member] 6.875% Notes [Member]	Dec. 31, 2012 PGS [Member] Long-Term Debt [Member] 6.375% Notes [Member]	Dec. 31, 2012 PGS [Member] Long-Term Debt [Member] 6.1% Notes [Member]	Dec. 31, 2012 PGS [Member] Long-Term Debt [Member] 5.4% Notes [Member]	Dec. 31, 2012 PGS [Member] Long-Term Debt [Member] 2.6% Notes [Member]	Dec. 31, 2012 PGS [Member] Long-Term Debt [Member] 6.15% Notes [Member]	Dec. 31, 2012 PGS [Member] Long-Term Debt [Member] 4.1% Notes [Member]	Dec. 31, 2012 PGS [Member] Long-Term Debt [Member] 8.00% Senior Notes [Member]	Dec. 31, 2012 Tampa Electric [Member] Long-Term Debt [Member] 1.5% term rate bonds repurchased in 2011 [Member]	Dec. 31, 2012 Tampa Electric [Member] Long-Term Debt [Member] 5.1% Refunding bonds [Member]	Dec. 31, 2012 Tampa Electric [Member] Long-Term Debt [Member] 5.65% Refunding bonds [Member]	Dec. 31, 2012 Tampa Electric [Member] Long-Term Debt [Member] 5.5% Refunding bonds [Member]	Dec. 31, 2012 Tampa Electric [Member] Long-Term Debt [Member] 5.15% Refunding bonds [Member]	Dec. 31, 2012 Tampa Electric [Member] Long-Term Debt [Member] 5.0% Refunding bonds [Member]	Dec. 31, 2012 Tampa Electric [Member] Long-Term Debt [Member] 6.875% Notes [Member]	Dec. 31, 2012 Tampa Electric [Member] Long-Term Debt [Member] 6.375% Notes [Member]	Dec. 31, 2012 Tampa Electric [Member] Long-Term Debt [Member] 6.25% Notes [Member]	Dec. 31, 2012 Tampa Electric [Member] Long-Term Debt [Member] 6.1% Notes [Member]	Dec. 31, 2012 Tampa Electric [Member] Long-Term Debt [Member] 5.4% Notes [Member]	Dec. 31, 2012 Tampa Electric [Member] Long-Term Debt [Member] 2.6% Notes [Member]	Dec. 31, 2012 Tampa Electric [Member] Long-Term Debt [Member] 6.55% Notes [Member]	Dec. 31, 2012 Tampa Electric [Member] Long-Term Debt [Member] 6.15% Notes [Member]	Dec. 31, 2012 Tampa Electric [Member] Long-Term Debt [Member] 4.1% Notes [Member]
Effective interest rate		7.10%	7.90%	7.00%	5.80%	2.70%	6.20%	4.20%			5.60%	5.90%	6.20%	5.40%	5.80%	7.10%	7.90%	6.30%	6.40%	5.90%	2.70%	6.60%	6.20%	4.20%
Stated interest rate		6.875%	6.375%	6.10%	5.40%	2.60%	6.15%	4.10%	8.00%	1.50%	5.10%	5.65%	5.50%	5.15%	5.00%	6.875%	6.375%	6.25%	6.10%	5.40%	2.60%	6.55%	6.15%	4.10%
Variable rate bonds, par amounts	$ 75.0