Long-Term Debt Long-Term Debt Textuals (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012 percent years
Issuance of Debt [Line Items]
Debt Instrument, Face Amount	$ 500
Additonal Interest on Deferred Debt Payments	5.25%
Mortgage Bonds Agreed to Sell	70
Interest Rate on Bonds Agreed to Sell	3.92%
Time Period on Mortgage Bonds Agreed to Sell	30
Junior Subordinated Debt [Member]
Issuance of Debt [Line Items]
Debt Instrument, Face Amount	$ 200
Debt Instrument, Interest Rate, Stated Percentage	5.25%

The stated principal amount of the debt instrument at time of issuance, which may vary from the carrying amount because of unamortized premium or discount.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 45

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28551-108399

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 55

-Paragraph 8

-URI http://asc.fasb.org/extlink&oid=6584090&loc=d3e28878-108400

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

-Publisher AICPA

-Name Accounting Principles Board Opinion (APB)

-Number 21

-Paragraph 16, 20

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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.

Name:	us-gaap_DebtInstrumentFaceAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant