Financial Instruments And Investments (Company's Decommissioning Trust Funds And Investments In Debt Securities) (Details) (USD $)	12 Months Ended
	Sep. 30, 2012	Dec. 31, 2011
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Proceeds from Sale of Trading Securities Held-for-investment		$ 2,000,000
Trading Securities, Realized Gain	400,000
Decommissioning Fund Investments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	186,724,000	167,963,000
Decommissioning Fund Investments [Member] \| Debt Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments in Debt Securities	1,254,000	1,120,000
Decommissioning Fund Investments [Member] \| Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	110,677,000	91,422,000
Decommissioning Fund Investments [Member] \| Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] \| Debt Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments in Debt Securities	0	0
Decommissioning Fund Investments [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	76,047,000	76,541,000
Decommissioning Fund Investments [Member] \| Significant Other Observable Inputs (Level 2) [Member] \| Debt Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments in Debt Securities	0	0
Decommissioning Fund Investments [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	0	0
Decommissioning Fund Investments [Member] \| Significant Unobservable Inputs (Level 3) [Member] \| Debt Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments in Debt Securities	1,254,000	1,120,000
Debt Securities [Member] \| Decommissioning Fund Investments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	92,971,000	89,317,000
Debt Securities [Member] \| Decommissioning Fund Investments [Member] \| Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	16,924,000	12,776,000
Debt Securities [Member] \| Decommissioning Fund Investments [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	76,047,000	76,541,000
Debt Securities [Member] \| Decommissioning Fund Investments [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	0	0
U.S. Government Bonds [Member] \| Decommissioning Fund Investments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	16,924,000	12,776,000
U.S. Government Bonds [Member] \| Decommissioning Fund Investments [Member] \| Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	16,924,000	12,776,000
U.S. Government Bonds [Member] \| Decommissioning Fund Investments [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	0	0
U.S. Government Bonds [Member] \| Decommissioning Fund Investments [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	0	0
Collateralized Mortgage Backed Securities [Member] \| Decommissioning Fund Investments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	21,307,000	26,825,000
Collateralized Mortgage Backed Securities [Member] \| Decommissioning Fund Investments [Member] \| Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	0	0
Collateralized Mortgage Backed Securities [Member] \| Decommissioning Fund Investments [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	21,307,000	26,825,000
Collateralized Mortgage Backed Securities [Member] \| Decommissioning Fund Investments [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	0	0
Municipal Bonds [Member] \| Decommissioning Fund Investments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	41,674,000	37,316,000
Municipal Bonds [Member] \| Decommissioning Fund Investments [Member] \| Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	0	0
Municipal Bonds [Member] \| Decommissioning Fund Investments [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	41,674,000	37,316,000
Municipal Bonds [Member] \| Decommissioning Fund Investments [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	0	0
Corporate Debt Securities [Member] \| Decommissioning Fund Investments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	13,066,000	12,400,000
Corporate Debt Securities [Member] \| Decommissioning Fund Investments [Member] \| Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	0	0
Corporate Debt Securities [Member] \| Decommissioning Fund Investments [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	13,066,000	12,400,000
Corporate Debt Securities [Member] \| Decommissioning Fund Investments [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	0	0
Equity Securities [Member] \| Decommissioning Fund Investments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	79,150,000	74,907,000
Equity Securities [Member] \| Decommissioning Fund Investments [Member] \| Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	79,150,000	74,907,000
Equity Securities [Member] \| Decommissioning Fund Investments [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	0	0
Equity Securities [Member] \| Decommissioning Fund Investments [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	0	0
Mutual Funds - Equity [Member] \| Decommissioning Fund Investments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	9,757,000
Mutual Funds - Equity [Member] \| Decommissioning Fund Investments [Member] \| Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	9,757,000
Mutual Funds - Equity [Member] \| Decommissioning Fund Investments [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	0
Mutual Funds - Equity [Member] \| Decommissioning Fund Investments [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	0
Cash and Cash Equivalents [Member] \| Decommissioning Fund Investments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	4,846,000	3,739,000
Cash and Cash Equivalents [Member] \| Decommissioning Fund Investments [Member] \| Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	4,846,000	3,739,000
Cash and Cash Equivalents [Member] \| Decommissioning Fund Investments [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	0	0
Cash and Cash Equivalents [Member] \| Decommissioning Fund Investments [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale securities	$ 0	$ 0

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents Available-for-sale Securities which consist of all investments in certain debt and equity securities neither classified as trading or held-to-maturity securities. A debt security represents a creditor relationship with an enterprise. Debt securities include, among other items, US Treasury securities, US government securities, municipal securities, corporate bonds, convertible debt, commercial paper, and all securitized debt instruments. An equity security represents an ownership interest in an enterprise or the right to acquire or dispose of an ownership interest in an enterprise at fixed or determinable prices. Equity securities include, among other things, common stock, certain preferred stock, warrant rights, call options, and put options, but do not include convertible debt. An entity may opt to provide the reader with additional narrative text to better understand the nature of investments in debt and equity securities which are categorized as Available-for-sale.

+ References+ Details

- Definition

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents Trading Securities which consist of all investments in certain debt and equity securities that are bought and held principally for the purpose of selling them in the near term (thus held for only a short period of time) or for which an entity has elected the fair value option. Trading generally reflects active and frequent buying and selling, and trading securities are generally used with the objective of generating profits on short-term differences in price, but this category of investments may also include items which are not intended to be sold in the near term or for which the fair value option has been elected.

+ References+ Details