Financial Instruments And Investments (Company's Decommissioning Trust Funds And Investments In Debt Securities) (Details) (USD $) In Thousands	Sep. 30, 2011	Dec. 31, 2010
Total Available for Sale	$ 158,437	$ 153,878
Municipal Debt Obligations [Member] \| Estimate of Fair Value, Fair Value Disclosure [Member]
Subtotal Debt Securities	34,967	32,541
Corporate Debt Securities [Member] \| Estimate of Fair Value, Fair Value Disclosure [Member]
Subtotal Debt Securities	11,813	9,077
Federal Agency Mortgage Backed Securities [Member] \| Estimate of Fair Value, Fair Value Disclosure [Member]
Subtotal Debt Securities	28,703	21,204
U.S. Government Bonds [Member] \| Estimate of Fair Value, Fair Value Disclosure [Member]
Subtotal Debt Securities	12,375	20,033
Estimate of Fair Value, Fair Value Disclosure [Member]
Investments in Debt Securities	2,776	2,909
Subtotal Debt Securities	87,858	82,855
Common Stock	65,764	68,016
Cash and Cash Equivalents	4,815	3,007
Total Available for Sale	158,437	153,878
Municipal Debt Obligations [Member] \| Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Subtotal Debt Securities	0	0
Corporate Debt Securities [Member] \| Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Subtotal Debt Securities	0	0
Federal Agency Mortgage Backed Securities [Member] \| Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Subtotal Debt Securities	0	0
U.S. Government Bonds [Member] \| Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Subtotal Debt Securities	12,375	20,033
Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Investments in Debt Securities	0	0
Subtotal Debt Securities	12,375	20,033
Common Stock	65,764	68,016
Cash and Cash Equivalents	4,815	3,007
Total Available for Sale	82,954	91,056
Municipal Debt Obligations [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Subtotal Debt Securities	34,967	32,541
Corporate Debt Securities [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Subtotal Debt Securities	11,813	9,077
Federal Agency Mortgage Backed Securities [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Subtotal Debt Securities	28,703	21,204
U.S. Government Bonds [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Subtotal Debt Securities	0	0
Significant Other Observable Inputs (Level 2) [Member]
Investments in Debt Securities	0	0
Subtotal Debt Securities	75,483	62,822
Common Stock	0	0
Cash and Cash Equivalents	0	0
Total Available for Sale	75,483	62,822
Municipal Debt Obligations [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Subtotal Debt Securities	0	0
Corporate Debt Securities [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Subtotal Debt Securities	0	0
Federal Agency Mortgage Backed Securities [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Subtotal Debt Securities	0	0
U.S. Government Bonds [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Subtotal Debt Securities	0	0
Significant Unobservable Inputs (Level 3) [Member]
Investments in Debt Securities	2,776	2,909
Subtotal Debt Securities	0	0
Common Stock	0	0
Cash and Cash Equivalents	0	0
Total Available for Sale	$ 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.

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 includes currency on hand as well as demand deposits with banks or financial institutions. It also includes other kinds of accounts that have the general characteristics of demand deposits in that the Company may deposit additional funds at any time and also effectively may withdraw funds at any time without prior notice or penalty. Cash equivalents, excluding items classified as marketable securities, include short-term, highly liquid investments that are both readily convertible to known amounts of cash, and so near their maturity that they present minimal risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three years ago does not become a cash equivalent when its remaining maturity is three months.

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- 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.

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