STATEMENTS OF CAPITALIZATION (Parenthetical) - $ / shares	12 Months Ended
Dec. 31, 2016	Dec. 31, 2015
Common Stockholder's Equity
Common stock, shares authorized (in shares)	200	200
Common stock, par value (in dollars per share)	$ 1.00	$ 1.00
Common stock, shares outstanding (in shares)	100	100
First Mortgage Bonds, Series due: \| Series Due June 15, 2024
Schedule of Capitalization, Long-term Debt [Line Items]
Maturity Date	Jun. 15, 2024	Jun. 15, 2024
Debt instrument, Interest Rate, Stated Percentage	3.30%	3.30%
First Mortgage Bonds, Series due: \| Series Due Aug. 15, 2041
Schedule of Capitalization, Long-term Debt [Line Items]
Maturity Date	Aug. 15, 2041	Aug. 15, 2041
Debt instrument, Interest Rate, Stated Percentage	4.50%	4.50%
First Mortgage Bonds, Series due: \| Series Due Aug. 15, 2046
Schedule of Capitalization, Long-term Debt [Line Items]
Maturity Date	Aug. 15, 2046	Aug. 15, 2046
Debt instrument, Interest Rate, Stated Percentage	3.40%	3.40%
Unsecured Senior Notes \| Senior E Due Oct. 1, 2016
Schedule of Capitalization, Long-term Debt [Line Items]
Maturity Date	Oct. 01, 2016	Oct. 01, 2016
Debt instrument, Interest Rate, Stated Percentage	5.60%	5.60%
Unsecured Senior Notes \| Senior G Due Dec. 1, 2018
Schedule of Capitalization, Long-term Debt [Line Items]
Maturity Date	Dec. 01, 2018	Dec. 01, 2018
Debt instrument, Interest Rate, Stated Percentage	8.75%	8.75%
Unsecured Senior Notes \| Senior C and D Due Oct. 1, 2033
Schedule of Capitalization, Long-term Debt [Line Items]
Maturity Date	Oct. 01, 2033	Oct. 01, 2033
Debt instrument, Interest Rate, Stated Percentage	6.00%	6.00%
Unsecured Senior Notes \| Senior F Due Oct. 1, 2036
Schedule of Capitalization, Long-term Debt [Line Items]
Maturity Date	Oct. 01, 2036	Oct. 01, 2036
Debt instrument, Interest Rate, Stated Percentage	6.00%	6.00%

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- Definition

Face amount or stated value per share of common stock.

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Number of shares of common stock outstanding. Common stock represent the ownership interest in a corporation.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(29))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21463-112644

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Contractual interest rate for funds borrowed, under the debt agreement.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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