Financial Instruments And Investments (Company's Decommissioning Trust Funds And Investments In Debt Securities) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Decommissioning Fund Investments
Financial Instruments and Investments [Line Items]
Available-for-sale Securities	$ 217,509	$ 214,095
Decommissioning Fund Investments | Quoted Prices In Active Markets For Identical Assets (Level 1)
Financial Instruments and Investments [Line Items]
Available-for-sale Securities	139,292	154,077
Decommissioning Fund Investments | Significant Other Observable Inputs (Level 2)
Financial Instruments and Investments [Line Items]
Available-for-sale Securities	78,217	60,018
Decommissioning Fund Investments | Significant Unobservable Inputs (Level 3)
Financial Instruments and Investments [Line Items]
Available-for-sale Securities	0	0
Debt Securities
Financial Instruments and Investments [Line Items]
Investments in Debt Securities	1,503	1,555
Debt Securities | Quoted Prices In Active Markets For Identical Assets (Level 1)
Financial Instruments and Investments [Line Items]
Investments in Debt Securities	0	0
Debt Securities | Significant Other Observable Inputs (Level 2)
Financial Instruments and Investments [Line Items]
Investments in Debt Securities	0	0
Debt Securities | Significant Unobservable Inputs (Level 3)
Financial Instruments and Investments [Line Items]
Investments in Debt Securities	1,503	1,555
Debt Securities | Decommissioning Fund Investments
Financial Instruments and Investments [Line Items]
Available-for-sale Securities	88,721	85,256
Debt Securities | Decommissioning Fund Investments | Quoted Prices In Active Markets For Identical Assets (Level 1)
Financial Instruments and Investments [Line Items]
Available-for-sale Securities	27,395	25,238
Debt Securities | Decommissioning Fund Investments | Significant Other Observable Inputs (Level 2)
Financial Instruments and Investments [Line Items]
Available-for-sale Securities	61,326	60,018
Debt Securities | Decommissioning Fund Investments | Significant Unobservable Inputs (Level 3)
Financial Instruments and Investments [Line Items]
Available-for-sale Securities	0	0
U.S. Government Bonds | Decommissioning Fund Investments
Financial Instruments and Investments [Line Items]
Available-for-sale Securities	27,395	25,238
U.S. Government Bonds | Decommissioning Fund Investments | Quoted Prices In Active Markets For Identical Assets (Level 1)
Financial Instruments and Investments [Line Items]
Available-for-sale Securities	27,395	25,238
U.S. Government Bonds | Decommissioning Fund Investments | Significant Other Observable Inputs (Level 2)
Financial Instruments and Investments [Line Items]
Available-for-sale Securities	0	0
U.S. Government Bonds | Decommissioning Fund Investments | Significant Unobservable Inputs (Level 3)
Financial Instruments and Investments [Line Items]
Available-for-sale Securities	0	0
Collateralized Mortgage Backed Securities | Decommissioning Fund Investments
Financial Instruments and Investments [Line Items]
Available-for-sale Securities	17,400	17,794
Collateralized Mortgage Backed Securities | Decommissioning Fund Investments | Quoted Prices In Active Markets For Identical Assets (Level 1)
Financial Instruments and Investments [Line Items]
Available-for-sale Securities	0	0
Collateralized Mortgage Backed Securities | Decommissioning Fund Investments | Significant Other Observable Inputs (Level 2)
Financial Instruments and Investments [Line Items]
Available-for-sale Securities	17,400	17,794
Collateralized Mortgage Backed Securities | Decommissioning Fund Investments | Significant Unobservable Inputs (Level 3)
Financial Instruments and Investments [Line Items]
Available-for-sale Securities	0	0
Municipal Bonds | Decommissioning Fund Investments
Financial Instruments and Investments [Line Items]
Available-for-sale Securities	30,135	28,851
Municipal Bonds | Decommissioning Fund Investments | Quoted Prices In Active Markets For Identical Assets (Level 1)
Financial Instruments and Investments [Line Items]
Available-for-sale Securities	0	0
Municipal Bonds | Decommissioning Fund Investments | Significant Other Observable Inputs (Level 2)
Financial Instruments and Investments [Line Items]
Available-for-sale Securities	30,135	28,851
Municipal Bonds | Decommissioning Fund Investments | Significant Unobservable Inputs (Level 3)
Financial Instruments and Investments [Line Items]
Available-for-sale Securities	0	0
Corporate Debt Securities | Decommissioning Fund Investments
Financial Instruments and Investments [Line Items]
Available-for-sale Securities	13,791	13,373
Corporate Debt Securities | Decommissioning Fund Investments | Quoted Prices In Active Markets For Identical Assets (Level 1)
Financial Instruments and Investments [Line Items]
Available-for-sale Securities	0	0
Corporate Debt Securities | Decommissioning Fund Investments | Significant Other Observable Inputs (Level 2)
Financial Instruments and Investments [Line Items]
Available-for-sale Securities	13,791	13,373
Corporate Debt Securities | Decommissioning Fund Investments | Significant Unobservable Inputs (Level 3)
Financial Instruments and Investments [Line Items]
Available-for-sale Securities	0	0
Equity Securities | Decommissioning Fund Investments
Financial Instruments and Investments [Line Items]
Available-for-sale Securities	107,449	106,113
Equity Securities | Decommissioning Fund Investments | Quoted Prices In Active Markets For Identical Assets (Level 1)
Financial Instruments and Investments [Line Items]
Available-for-sale Securities	107,449	106,113
Equity Securities | Decommissioning Fund Investments | Significant Other Observable Inputs (Level 2)
Financial Instruments and Investments [Line Items]
Available-for-sale Securities	0	0
Equity Securities | Decommissioning Fund Investments | Significant Unobservable Inputs (Level 3)
Financial Instruments and Investments [Line Items]
Available-for-sale Securities	0	0
Common Collective Trust - Equity Funds | Decommissioning Fund Investments
Financial Instruments and Investments [Line Items]
Available-for-sale Securities	16,891
Common Collective Trust - Equity Funds | Decommissioning Fund Investments | Quoted Prices In Active Markets For Identical Assets (Level 1)
Financial Instruments and Investments [Line Items]
Available-for-sale Securities	0
Common Collective Trust - Equity Funds | Decommissioning Fund Investments | Significant Other Observable Inputs (Level 2)
Financial Instruments and Investments [Line Items]
Available-for-sale Securities	16,891
Common Collective Trust - Equity Funds | Decommissioning Fund Investments | Significant Unobservable Inputs (Level 3)
Financial Instruments and Investments [Line Items]
Available-for-sale Securities	0
Equity Mutual Funds | Decommissioning Fund Investments
Financial Instruments and Investments [Line Items]
Available-for-sale Securities		16,802
Equity Mutual Funds | Decommissioning Fund Investments | Quoted Prices In Active Markets For Identical Assets (Level 1)
Financial Instruments and Investments [Line Items]
Available-for-sale Securities		16,802
Equity Mutual Funds | Decommissioning Fund Investments | Significant Other Observable Inputs (Level 2)
Financial Instruments and Investments [Line Items]
Available-for-sale Securities		0
Equity Mutual Funds | Decommissioning Fund Investments | Significant Unobservable Inputs (Level 3)
Financial Instruments and Investments [Line Items]
Available-for-sale Securities		0
Cash and Cash Equivalents | Decommissioning Fund Investments
Financial Instruments and Investments [Line Items]
Available-for-sale Securities	4,448	5,924
Cash and Cash Equivalents | Decommissioning Fund Investments | Quoted Prices In Active Markets For Identical Assets (Level 1)
Financial Instruments and Investments [Line Items]
Available-for-sale Securities	4,448	5,924
Cash and Cash Equivalents | Decommissioning Fund Investments | Significant Other Observable Inputs (Level 2)
Financial Instruments and Investments [Line Items]
Available-for-sale Securities	0	0
Cash and Cash Equivalents | Decommissioning Fund Investments | Significant Unobservable Inputs (Level 3)
Financial Instruments and Investments [Line Items]
Available-for-sale Securities	$ 0	$ 0