Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities
Net income	$ 316	$ 286	$ 276
Adjustments to reconcile net income to net cash from operating activities:
Depreciation and amortization	350	328	313
Deferred income taxes and investment tax credits	192	87	120
Allowance for equity funds used during construction	(2)	(24)	(17)
Deferred recovery clauses	(83)	54	26
Receivables, less allowance for uncollectibles	(43)	18	(3)
Inventories	13	16	(21)
Taxes accrued	(9)	68	(17)
Accounts payable	(16)	63	(27)
Regulatory assets and liabilities	(100)	(11)	(9)
Other	(6)	(54)	(33)
Cash flows from operating activities	612	831	608
Cash flows from investing activities
Capital expenditures	(640)	(727)	(687)
Net proceeds from sale of assets	0	9	0
Cash flows used in investing activities	(640)	(718)	(687)
Cash flows from financing activities
Equity contributions from TECO Energy	190	150
Proceeds from long-term debt issuance	0	0	251
Repayment of long-term debt	0	(83)	(83)
Net change in short-term debt (maturities of 90 days or less)	(165)	109	3
Proceeds from other short-term debt (maturities over 90 days)	300	0	0
Dividends to TECO Energy	(292)	(289)
Other financing activities	(2)	1	0
Cash flows from/(used in) financing activities	31	(112)	78
Net increase (decrease) in cash and cash equivalents	3	1	(1)
Cash and cash equivalents at beginning of the year	10	9	10
Cash and cash equivalents at end of the year	13	10	9
Supplemental disclosure of cash paid (received):
Interest	115	103	106
Income taxes	13	(3)	64
Supplemental disclosure of non-cash activities
Change in accrued capital expenditures	(16)	(9)	7
TECO Energy [Member]
Cash flows from financing activities
Equity contributions from TECO Energy	190	150	175
Dividends to TECO Energy	$ (292)	$ (289)	$ (268)