STATEMENTS OF CAPITALIZATION (Parenthetical) (Unsecured Senior Notes [Member], USD $)	12 Months Ended
Dec. 31, 2012 Senior E Due Oct. 1, 2016 [Member]	Dec. 31, 2012 Senior G Due Dec. 1, 2018 [Member]	Dec. 31, 2012 Senior C and D Due Oct. 1, 2033 [Member]	Dec. 31, 2012 Senior F Due Oct. 1, 2036 [Member]
Long-Term Debt
Debt instrument, interest rate stated percentage (in hundredths)	5.60%	8.75%	6.00%	6.00%
Debt instrument, maturity date	Oct. 01, 2016	Dec. 01, 2018	Oct. 01, 2033	Oct. 01, 2036

Date when the debt instrument is scheduled to be fully repaid, which may be presented in a variety of ways (year, month and year, day, month and year, quarter, etc.).

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 129

-Paragraph 2, 4

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.22(a)(2))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Name:	us-gaap_DebtInstrumentMaturityDate
Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration