Employee Postretirement Benefits - Schedule of Fair Value Hierarchy Plan's Investments (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 593,000,000	$ 529,100,000
Commingled Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		214,800,000
Accounts Receivable [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	44,700,000	64,800,000
Accounts Payable [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	(40,800,000)	(72,800,000)
Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	18,900,000	35,300,000
Cash Equivalents [Member] | Short Term Investment Fund (STIF) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	7,900,000	9,000,000
Cash Equivalents [Member] | Treasury Bills (T bills) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	300,000	600,000
Cash Equivalents [Member] | Repurchase Agreements [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	8,800,000	23,100,000
Cash Equivalents [Member] | Commercial Paper [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	400,000	900,000
Cash Equivalents [Member] | Money Markets [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,500,000	600,000
Cash Equivalents [Member] | Certificates of Deposit [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		1,100,000
Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	319,700,000	287,700,000
Equity Securities [Member] | Common Stock [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	91,600,000	125,300,000
Equity Securities [Member] | American Depository Receipt (ADR) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3,000,000	6,200,000
Equity Securities [Member] | Real Estate Investment Trust (REIT) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,700,000	2,000,000
Equity Securities [Member] | Preferred Stocks [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	800,000	800,000
Equity Securities [Member] | Equity Mutual Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	172,600,000	153,400,000
Equity Securities [Member] | Commingled Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	50,000,000
Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	251,200,000	63,700,000
Debt Securities [Member] | Commingled Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	94,100,000
Debt Securities [Member] | Municipal Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	7,300,000	8,000,000
Debt Securities [Member] | Government Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	35,700,000	53,000,000
Debt Securities [Member] | Corporate Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	19,600,000	19,800,000
Debt Securities [Member] | Asset Backed Securities (ABS) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	400,000	500,000
Debt Securities [Member] | Mortgage Back Securities (MBS) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	6,700,000	17,600,000
Debt Securities [Member] | CMO [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2,300,000	2,500,000
Debt Securities [Member] | Fixed Income Mutual Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	85,100,000
Debt Securities [Member] | Commercial Mortgage Backed Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		300,000
Derivative [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	(900,000)	(800,000)
Derivative [Member] | Short Term Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	200,000
Derivative [Member] | Swaps [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	(900,000)	(500,000)
Derivative [Member] | Purchased Options [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	200,000	100,000
Derivative [Member] | Written Options [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	(400,000)	(400,000)
Miscellaneous [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	200,000	100,000
Fixed Income Mutual Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		49,400,000
Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	280,700,000	287,900,000
Level 1 [Member] | Commingled Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0
Level 1 [Member] | Accounts Receivable [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	44,700,000	64,800,000
Level 1 [Member] | Accounts Payable [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	(40,800,000)	(72,800,000)
Level 1 [Member] | Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	7,900,000	9,000,000
Level 1 [Member] | Cash Equivalents [Member] | Short Term Investment Fund (STIF) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	7,900,000	9,000,000
Level 1 [Member] | Cash Equivalents [Member] | Treasury Bills (T bills) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 1 [Member] | Cash Equivalents [Member] | Repurchase Agreements [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 1 [Member] | Cash Equivalents [Member] | Commercial Paper [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 1 [Member] | Cash Equivalents [Member] | Money Markets [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 1 [Member] | Cash Equivalents [Member] | Certificates of Deposit [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0
Level 1 [Member] | Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	268,900,000	286,900,000
Level 1 [Member] | Equity Securities [Member] | Common Stock [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	91,600,000	125,300,000
Level 1 [Member] | Equity Securities [Member] | American Depository Receipt (ADR) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3,000,000	6,200,000
Level 1 [Member] | Equity Securities [Member] | Real Estate Investment Trust (REIT) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,700,000	2,000,000
Level 1 [Member] | Equity Securities [Member] | Preferred Stocks [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 1 [Member] | Equity Securities [Member] | Equity Mutual Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	172,600,000	153,400,000
Level 1 [Member] | Equity Securities [Member] | Commingled Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0
Level 1 [Member] | Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 1 [Member] | Debt Securities [Member] | Commingled Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0
Level 1 [Member] | Debt Securities [Member] | Municipal Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 1 [Member] | Debt Securities [Member] | Government Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 1 [Member] | Debt Securities [Member] | Corporate Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 1 [Member] | Debt Securities [Member] | Asset Backed Securities (ABS) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 1 [Member] | Debt Securities [Member] | Mortgage Back Securities (MBS) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 1 [Member] | Debt Securities [Member] | CMO [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 1 [Member] | Debt Securities [Member] | Fixed Income Mutual Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0
Level 1 [Member] | Debt Securities [Member] | Commercial Mortgage Backed Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0
Level 1 [Member] | Derivative [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 1 [Member] | Derivative [Member] | Short Term Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0
Level 1 [Member] | Derivative [Member] | Swaps [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 1 [Member] | Derivative [Member] | Purchased Options [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 1 [Member] | Derivative [Member] | Written Options [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 1 [Member] | Miscellaneous [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 1 [Member] | Fixed Income Mutual Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0
Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	312,300,000	241,200,000
Level 2 [Member] | Commingled Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		214,800,000
Level 2 [Member] | Accounts Receivable [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 2 [Member] | Accounts Payable [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 2 [Member] | Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	11,000,000	26,300,000
Level 2 [Member] | Cash Equivalents [Member] | Short Term Investment Fund (STIF) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 2 [Member] | Cash Equivalents [Member] | Treasury Bills (T bills) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	300,000	600,000
Level 2 [Member] | Cash Equivalents [Member] | Repurchase Agreements [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	8,800,000	23,100,000
Level 2 [Member] | Cash Equivalents [Member] | Commercial Paper [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	400,000	900,000
Level 2 [Member] | Cash Equivalents [Member] | Money Markets [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,500,000	600,000
Level 2 [Member] | Cash Equivalents [Member] | Certificates of Deposit [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		1,100,000
Level 2 [Member] | Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	50,800,000	800,000
Level 2 [Member] | Equity Securities [Member] | Common Stock [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 2 [Member] | Equity Securities [Member] | American Depository Receipt (ADR) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 2 [Member] | Equity Securities [Member] | Real Estate Investment Trust (REIT) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 2 [Member] | Equity Securities [Member] | Preferred Stocks [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	800,000	800,000
Level 2 [Member] | Equity Securities [Member] | Equity Mutual Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 2 [Member] | Equity Securities [Member] | Commingled Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	50,000,000
Level 2 [Member] | Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	251,200,000	63,700,000
Level 2 [Member] | Debt Securities [Member] | Commingled Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	94,100,000
Level 2 [Member] | Debt Securities [Member] | Municipal Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	7,300,000	8,000,000
Level 2 [Member] | Debt Securities [Member] | Government Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	35,700,000	53,000,000
Level 2 [Member] | Debt Securities [Member] | Corporate Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	19,600,000	19,800,000
Level 2 [Member] | Debt Securities [Member] | Asset Backed Securities (ABS) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	400,000	500,000
Level 2 [Member] | Debt Securities [Member] | Mortgage Back Securities (MBS) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	6,700,000	17,600,000
Level 2 [Member] | Debt Securities [Member] | CMO [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2,300,000	2,500,000
Level 2 [Member] | Debt Securities [Member] | Fixed Income Mutual Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	85,100,000
Level 2 [Member] | Debt Securities [Member] | Commercial Mortgage Backed Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		300,000
Level 2 [Member] | Derivative [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	(900,000)	(800,000)
Level 2 [Member] | Derivative [Member] | Short Term Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	200,000
Level 2 [Member] | Derivative [Member] | Swaps [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	(900,000)	(500,000)
Level 2 [Member] | Derivative [Member] | Purchased Options [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	200,000	100,000
Level 2 [Member] | Derivative [Member] | Written Options [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	(400,000)	(400,000)
Level 2 [Member] | Miscellaneous [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	200,000	100,000
Level 2 [Member] | Fixed Income Mutual Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		49,400,000
Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 3 [Member] | Commingled Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0
Level 3 [Member] | Accounts Receivable [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 3 [Member] | Accounts Payable [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 3 [Member] | Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 3 [Member] | Cash Equivalents [Member] | Short Term Investment Fund (STIF) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 3 [Member] | Cash Equivalents [Member] | Treasury Bills (T bills) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 3 [Member] | Cash Equivalents [Member] | Repurchase Agreements [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 3 [Member] | Cash Equivalents [Member] | Commercial Paper [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 3 [Member] | Cash Equivalents [Member] | Money Markets [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 3 [Member] | Cash Equivalents [Member] | Certificates of Deposit [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0
Level 3 [Member] | Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 3 [Member] | Equity Securities [Member] | Common Stock [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 3 [Member] | Equity Securities [Member] | American Depository Receipt (ADR) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 3 [Member] | Equity Securities [Member] | Real Estate Investment Trust (REIT) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 3 [Member] | Equity Securities [Member] | Preferred Stocks [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 3 [Member] | Equity Securities [Member] | Equity Mutual Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 3 [Member] | Equity Securities [Member] | Commingled Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0
Level 3 [Member] | Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 3 [Member] | Debt Securities [Member] | Commingled Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0
Level 3 [Member] | Debt Securities [Member] | Municipal Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 3 [Member] | Debt Securities [Member] | Government Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 3 [Member] | Debt Securities [Member] | Corporate Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 3 [Member] | Debt Securities [Member] | Asset Backed Securities (ABS) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 3 [Member] | Debt Securities [Member] | Mortgage Back Securities (MBS) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 3 [Member] | Debt Securities [Member] | CMO [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 3 [Member] | Debt Securities [Member] | Fixed Income Mutual Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0
Level 3 [Member] | Debt Securities [Member] | Commercial Mortgage Backed Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0
Level 3 [Member] | Derivative [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 3 [Member] | Derivative [Member] | Short Term Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0
Level 3 [Member] | Derivative [Member] | Swaps [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 3 [Member] | Derivative [Member] | Purchased Options [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 3 [Member] | Derivative [Member] | Written Options [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 3 [Member] | Miscellaneous [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 3 [Member] | Fixed Income Mutual Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0
Tampa Electric Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	593,000,000	529,100,000
Tampa Electric Company [Member] | Accounts Receivable [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	44,700,000	64,800,000
Tampa Electric Company [Member] | Accounts Payable [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	(40,800,000)	(72,800,000)
Tampa Electric Company [Member] | Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	18,900,000	35,300,000
Tampa Electric Company [Member] | Cash Equivalents [Member] | Short Term Investment Fund (STIF) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	7,900,000	9,000,000
Tampa Electric Company [Member] | Cash Equivalents [Member] | Treasury Bills (T bills) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	300,000	600,000
Tampa Electric Company [Member] | Cash Equivalents [Member] | Repurchase Agreements [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	8,800,000	23,100,000
Tampa Electric Company [Member] | Cash Equivalents [Member] | Commercial Paper [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	400,000	900,000
Tampa Electric Company [Member] | Cash Equivalents [Member] | Money Markets [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,500,000	600,000
Tampa Electric Company [Member] | Cash Equivalents [Member] | Certificates of Deposit [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		1,100,000
Tampa Electric Company [Member] | Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	319,700,000	287,700,000
Tampa Electric Company [Member] | Equity Securities [Member] | Common Stock [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	91,600,000	125,300,000
Tampa Electric Company [Member] | Equity Securities [Member] | American Depository Receipt (ADR) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3,000,000	6,200,000
Tampa Electric Company [Member] | Equity Securities [Member] | Real Estate Investment Trust (REIT) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,700,000	2,000,000
Tampa Electric Company [Member] | Equity Securities [Member] | Preferred Stocks [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	800,000	800,000
Tampa Electric Company [Member] | Equity Securities [Member] | Equity Mutual Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	172,600,000	153,400,000
Tampa Electric Company [Member] | Equity Securities [Member] | Commingled Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	50,000,000
Tampa Electric Company [Member] | Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	251,200,000	214,800,000
Tampa Electric Company [Member] | Debt Securities [Member] | Commingled Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	94,100,000	49,400,000
Tampa Electric Company [Member] | Debt Securities [Member] | Municipal Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	7,300,000	8,000,000
Tampa Electric Company [Member] | Debt Securities [Member] | Government Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	35,700,000	53,000,000
Tampa Electric Company [Member] | Debt Securities [Member] | Corporate Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	19,600,000	19,800,000
Tampa Electric Company [Member] | Debt Securities [Member] | Asset Backed Securities (ABS) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	400,000	500,000
Tampa Electric Company [Member] | Debt Securities [Member] | Mortgage Back Securities (MBS) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	6,700,000	17,600,000
Tampa Electric Company [Member] | Debt Securities [Member] | CMO [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2,300,000	2,500,000
Tampa Electric Company [Member] | Debt Securities [Member] | Fixed Income Mutual Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	85,100,000	63,700,000
Tampa Electric Company [Member] | Debt Securities [Member] | Commercial Mortgage Backed Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		300,000
Tampa Electric Company [Member] | Derivative [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	(900,000)	(800,000)
Tampa Electric Company [Member] | Derivative [Member] | Short Term Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	200,000
Tampa Electric Company [Member] | Derivative [Member] | Swaps [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	(900,000)	(500,000)
Tampa Electric Company [Member] | Derivative [Member] | Purchased Options [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	200,000	100,000
Tampa Electric Company [Member] | Derivative [Member] | Written Options [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	(400,000)	(400,000)
Tampa Electric Company [Member] | Miscellaneous [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	200,000	100,000
Tampa Electric Company [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	280,700,000	287,900,000
Tampa Electric Company [Member] | Level 1 [Member] | Accounts Receivable [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	44,700,000	64,800,000
Tampa Electric Company [Member] | Level 1 [Member] | Accounts Payable [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	(40,800,000)	(72,800,000)
Tampa Electric Company [Member] | Level 1 [Member] | Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	7,900,000	9,000,000
Tampa Electric Company [Member] | Level 1 [Member] | Cash Equivalents [Member] | Short Term Investment Fund (STIF) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	7,900,000	9,000,000
Tampa Electric Company [Member] | Level 1 [Member] | Cash Equivalents [Member] | Treasury Bills (T bills) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Tampa Electric Company [Member] | Level 1 [Member] | Cash Equivalents [Member] | Repurchase Agreements [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Tampa Electric Company [Member] | Level 1 [Member] | Cash Equivalents [Member] | Commercial Paper [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Tampa Electric Company [Member] | Level 1 [Member] | Cash Equivalents [Member] | Money Markets [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Tampa Electric Company [Member] | Level 1 [Member] | Cash Equivalents [Member] | Certificates of Deposit [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0
Tampa Electric Company [Member] | Level 1 [Member] | Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	268,900,000	286,900,000
Tampa Electric Company [Member] | Level 1 [Member] | Equity Securities [Member] | Common Stock [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	91,600,000	125,300,000
Tampa Electric Company [Member] | Level 1 [Member] | Equity Securities [Member] | American Depository Receipt (ADR) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3,000,000	6,200,000
Tampa Electric Company [Member] | Level 1 [Member] | Equity Securities [Member] | Real Estate Investment Trust (REIT) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,700,000	2,000,000
Tampa Electric Company [Member] | Level 1 [Member] | Equity Securities [Member] | Preferred Stocks [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Tampa Electric Company [Member] | Level 1 [Member] | Equity Securities [Member] | Equity Mutual Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	172,600,000	153,400,000
Tampa Electric Company [Member] | Level 1 [Member] | Equity Securities [Member] | Commingled Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0
Tampa Electric Company [Member] | Level 1 [Member] | Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Tampa Electric Company [Member] | Level 1 [Member] | Debt Securities [Member] | Commingled Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Tampa Electric Company [Member] | Level 1 [Member] | Debt Securities [Member] | Municipal Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Tampa Electric Company [Member] | Level 1 [Member] | Debt Securities [Member] | Government Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Tampa Electric Company [Member] | Level 1 [Member] | Debt Securities [Member] | Corporate Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Tampa Electric Company [Member] | Level 1 [Member] | Debt Securities [Member] | Asset Backed Securities (ABS) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Tampa Electric Company [Member] | Level 1 [Member] | Debt Securities [Member] | Mortgage Back Securities (MBS) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Tampa Electric Company [Member] | Level 1 [Member] | Debt Securities [Member] | CMO [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Tampa Electric Company [Member] | Level 1 [Member] | Debt Securities [Member] | Fixed Income Mutual Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Tampa Electric Company [Member] | Level 1 [Member] | Debt Securities [Member] | Commercial Mortgage Backed Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0
Tampa Electric Company [Member] | Level 1 [Member] | Derivative [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Tampa Electric Company [Member] | Level 1 [Member] | Derivative [Member] | Short Term Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0
Tampa Electric Company [Member] | Level 1 [Member] | Derivative [Member] | Swaps [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Tampa Electric Company [Member] | Level 1 [Member] | Derivative [Member] | Purchased Options [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Tampa Electric Company [Member] | Level 1 [Member] | Derivative [Member] | Written Options [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Tampa Electric Company [Member] | Level 1 [Member] | Miscellaneous [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Tampa Electric Company [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	312,300,000	241,200,000
Tampa Electric Company [Member] | Level 2 [Member] | Accounts Receivable [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Tampa Electric Company [Member] | Level 2 [Member] | Accounts Payable [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Tampa Electric Company [Member] | Level 2 [Member] | Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	11,000,000	26,300,000
Tampa Electric Company [Member] | Level 2 [Member] | Cash Equivalents [Member] | Short Term Investment Fund (STIF) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Tampa Electric Company [Member] | Level 2 [Member] | Cash Equivalents [Member] | Treasury Bills (T bills) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	300,000	600,000
Tampa Electric Company [Member] | Level 2 [Member] | Cash Equivalents [Member] | Repurchase Agreements [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	8,800,000	23,100,000
Tampa Electric Company [Member] | Level 2 [Member] | Cash Equivalents [Member] | Commercial Paper [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	400,000	900,000
Tampa Electric Company [Member] | Level 2 [Member] | Cash Equivalents [Member] | Money Markets [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,500,000	600,000
Tampa Electric Company [Member] | Level 2 [Member] | Cash Equivalents [Member] | Certificates of Deposit [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		1,100,000
Tampa Electric Company [Member] | Level 2 [Member] | Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	50,800,000	800,000
Tampa Electric Company [Member] | Level 2 [Member] | Equity Securities [Member] | Common Stock [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Tampa Electric Company [Member] | Level 2 [Member] | Equity Securities [Member] | American Depository Receipt (ADR) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Tampa Electric Company [Member] | Level 2 [Member] | Equity Securities [Member] | Real Estate Investment Trust (REIT) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Tampa Electric Company [Member] | Level 2 [Member] | Equity Securities [Member] | Preferred Stocks [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	800,000	800,000
Tampa Electric Company [Member] | Level 2 [Member] | Equity Securities [Member] | Equity Mutual Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Tampa Electric Company [Member] | Level 2 [Member] | Equity Securities [Member] | Commingled Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	50,000,000
Tampa Electric Company [Member] | Level 2 [Member] | Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	251,200,000	214,800,000
Tampa Electric Company [Member] | Level 2 [Member] | Debt Securities [Member] | Commingled Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	94,100,000	49,400,000
Tampa Electric Company [Member] | Level 2 [Member] | Debt Securities [Member] | Municipal Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	7,300,000	8,000,000
Tampa Electric Company [Member] | Level 2 [Member] | Debt Securities [Member] | Government Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	35,700,000	53,000,000
Tampa Electric Company [Member] | Level 2 [Member] | Debt Securities [Member] | Corporate Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	19,600,000	19,800,000
Tampa Electric Company [Member] | Level 2 [Member] | Debt Securities [Member] | Asset Backed Securities (ABS) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	400,000	500,000
Tampa Electric Company [Member] | Level 2 [Member] | Debt Securities [Member] | Mortgage Back Securities (MBS) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	6,700,000	17,600,000
Tampa Electric Company [Member] | Level 2 [Member] | Debt Securities [Member] | CMO [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2,300,000	2,500,000
Tampa Electric Company [Member] | Level 2 [Member] | Debt Securities [Member] | Fixed Income Mutual Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	85,100,000	63,700,000
Tampa Electric Company [Member] | Level 2 [Member] | Debt Securities [Member] | Commercial Mortgage Backed Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		300,000
Tampa Electric Company [Member] | Level 2 [Member] | Derivative [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	(900,000)	(800,000)
Tampa Electric Company [Member] | Level 2 [Member] | Derivative [Member] | Short Term Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	200,000
Tampa Electric Company [Member] | Level 2 [Member] | Derivative [Member] | Swaps [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	(900,000)	(500,000)
Tampa Electric Company [Member] | Level 2 [Member] | Derivative [Member] | Purchased Options [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	200,000	100,000
Tampa Electric Company [Member] | Level 2 [Member] | Derivative [Member] | Written Options [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	(400,000)	(400,000)
Tampa Electric Company [Member] | Level 2 [Member] | Miscellaneous [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	200,000	100,000
Tampa Electric Company [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Tampa Electric Company [Member] | Level 3 [Member] | Accounts Receivable [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Tampa Electric Company [Member] | Level 3 [Member] | Accounts Payable [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Tampa Electric Company [Member] | Level 3 [Member] | Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Tampa Electric Company [Member] | Level 3 [Member] | Cash Equivalents [Member] | Short Term Investment Fund (STIF) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Tampa Electric Company [Member] | Level 3 [Member] | Cash Equivalents [Member] | Treasury Bills (T bills) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Tampa Electric Company [Member] | Level 3 [Member] | Cash Equivalents [Member] | Repurchase Agreements [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Tampa Electric Company [Member] | Level 3 [Member] | Cash Equivalents [Member] | Commercial Paper [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Tampa Electric Company [Member] | Level 3 [Member] | Cash Equivalents [Member] | Money Markets [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Tampa Electric Company [Member] | Level 3 [Member] | Cash Equivalents [Member] | Certificates of Deposit [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0
Tampa Electric Company [Member] | Level 3 [Member] | Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Tampa Electric Company [Member] | Level 3 [Member] | Equity Securities [Member] | Common Stock [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Tampa Electric Company [Member] | Level 3 [Member] | Equity Securities [Member] | American Depository Receipt (ADR) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Tampa Electric Company [Member] | Level 3 [Member] | Equity Securities [Member] | Real Estate Investment Trust (REIT) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Tampa Electric Company [Member] | Level 3 [Member] | Equity Securities [Member] | Preferred Stocks [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Tampa Electric Company [Member] | Level 3 [Member] | Equity Securities [Member] | Equity Mutual Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Tampa Electric Company [Member] | Level 3 [Member] | Equity Securities [Member] | Commingled Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0
Tampa Electric Company [Member] | Level 3 [Member] | Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Tampa Electric Company [Member] | Level 3 [Member] | Debt Securities [Member] | Commingled Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Tampa Electric Company [Member] | Level 3 [Member] | Debt Securities [Member] | Municipal Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Tampa Electric Company [Member] | Level 3 [Member] | Debt Securities [Member] | Government Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Tampa Electric Company [Member] | Level 3 [Member] | Debt Securities [Member] | Corporate Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Tampa Electric Company [Member] | Level 3 [Member] | Debt Securities [Member] | Asset Backed Securities (ABS) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Tampa Electric Company [Member] | Level 3 [Member] | Debt Securities [Member] | Mortgage Back Securities (MBS) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Tampa Electric Company [Member] | Level 3 [Member] | Debt Securities [Member] | CMO [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Tampa Electric Company [Member] | Level 3 [Member] | Debt Securities [Member] | Fixed Income Mutual Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Tampa Electric Company [Member] | Level 3 [Member] | Debt Securities [Member] | Commercial Mortgage Backed Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0
Tampa Electric Company [Member] | Level 3 [Member] | Derivative [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Tampa Electric Company [Member] | Level 3 [Member] | Derivative [Member] | Short Term Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0
Tampa Electric Company [Member] | Level 3 [Member] | Derivative [Member] | Swaps [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Tampa Electric Company [Member] | Level 3 [Member] | Derivative [Member] | Purchased Options [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Tampa Electric Company [Member] | Level 3 [Member] | Derivative [Member] | Written Options [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Tampa Electric Company [Member] | Level 3 [Member] | Miscellaneous [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 0	$ 0