Financial Instruments and Risk Management (Fair Value Of Assets And Liabilities) (Details) - USD ($) $ in Thousands | 9 Months Ended | |
Sep. 30, 2016 | Dec. 31, 2015 |
Financial and Derivative Instruments and Trading Securities [Line Items] | | | |
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Redemption Restriction Period | [1] | 15 years | |
Nuclear decommissioning trust assets | | $ 198,796 | $ 184,057 |
Trading securities | | 34,495 | 33,888 |
Total assets measured at fair value | | 233,291 | 217,945 |
Level 1 [Member] | | | |
Financial and Derivative Instruments and Trading Securities [Line Items] | | | |
Nuclear decommissioning trust assets | | 201 | 87 |
Trading securities | | 0 | 159 |
Total assets measured at fair value | | 201 | 246 |
Level 2 [Member] | | | |
Financial and Derivative Instruments and Trading Securities [Line Items] | | | |
Nuclear decommissioning trust assets | | 165,801 | 150,658 |
Trading securities | | 34,495 | 33,729 |
Total assets measured at fair value | | 200,296 | 184,387 |
Level 3 [Member] | | | |
Financial and Derivative Instruments and Trading Securities [Line Items] | | | |
Nuclear decommissioning trust assets | | 0 | 0 |
Trading securities | | 0 | 0 |
Total assets measured at fair value | | 0 | 0 |
Domestic Equity [Member] | | | |
Financial and Derivative Instruments and Trading Securities [Line Items] | | | |
Nuclear decommissioning trust assets | | 59,121 | 56,922 |
Trading securities | | 18,004 | 17,876 |
Domestic Equity [Member] | Level 1 [Member] | | | |
Financial and Derivative Instruments and Trading Securities [Line Items] | | | |
Nuclear decommissioning trust assets | | 0 | 0 |
Trading securities | | 0 | 0 |
Domestic Equity [Member] | Level 2 [Member] | | | |
Financial and Derivative Instruments and Trading Securities [Line Items] | | | |
Nuclear decommissioning trust assets | | 53,950 | 50,872 |
Trading securities | | 18,004 | 17,876 |
Domestic Equity [Member] | Level 3 [Member] | | | |
Financial and Derivative Instruments and Trading Securities [Line Items] | | | |
Nuclear decommissioning trust assets | | 0 | 0 |
Trading securities | | 0 | 0 |
International Equity [Member] | | | |
Financial and Derivative Instruments and Trading Securities [Line Items] | | | |
Nuclear decommissioning trust assets | | 37,357 | 33,595 |
Trading securities | | 4,482 | 4,430 |
International Equity [Member] | Level 1 [Member] | | | |
Financial and Derivative Instruments and Trading Securities [Line Items] | | | |
Nuclear decommissioning trust assets | | 0 | 0 |
Trading securities | | 0 | 0 |
International Equity [Member] | Level 2 [Member] | | | |
Financial and Derivative Instruments and Trading Securities [Line Items] | | | |
Nuclear decommissioning trust assets | | 37,357 | 33,595 |
Trading securities | | 4,482 | 4,430 |
International Equity [Member] | Level 3 [Member] | | | |
Financial and Derivative Instruments and Trading Securities [Line Items] | | | |
Nuclear decommissioning trust assets | | 0 | 0 |
Trading securities | | 0 | 0 |
Core Bonds [Member] | | | |
Financial and Derivative Instruments and Trading Securities [Line Items] | | | |
Nuclear decommissioning trust assets | | 27,985 | 25,976 |
Trading securities | | 12,009 | 11,423 |
Core Bonds [Member] | Level 1 [Member] | | | |
Financial and Derivative Instruments and Trading Securities [Line Items] | | | |
Nuclear decommissioning trust assets | | 0 | 0 |
Trading securities | | 0 | 0 |
Core Bonds [Member] | Level 2 [Member] | | | |
Financial and Derivative Instruments and Trading Securities [Line Items] | | | |
Nuclear decommissioning trust assets | | 27,985 | 25,976 |
Trading securities | | 12,009 | 11,423 |
Core Bonds [Member] | Level 3 [Member] | | | |
Financial and Derivative Instruments and Trading Securities [Line Items] | | | |
Nuclear decommissioning trust assets | | 0 | 0 |
Trading securities | | 0 | 0 |
High-Yield Bonds [Member] | | | |
Financial and Derivative Instruments and Trading Securities [Line Items] | | | |
Nuclear decommissioning trust assets | | 17,686 | 15,288 |
High-Yield Bonds [Member] | Level 1 [Member] | | | |
Financial and Derivative Instruments and Trading Securities [Line Items] | | | |
Nuclear decommissioning trust assets | | 0 | 0 |
High-Yield Bonds [Member] | Level 2 [Member] | | | |
Financial and Derivative Instruments and Trading Securities [Line Items] | | | |
Nuclear decommissioning trust assets | | 17,686 | 15,288 |
High-Yield Bonds [Member] | Level 3 [Member] | | | |
Financial and Derivative Instruments and Trading Securities [Line Items] | | | |
Nuclear decommissioning trust assets | | 0 | 0 |
Emerging Market Bonds [Member] | | | |
Financial and Derivative Instruments and Trading Securities [Line Items] | | | |
Nuclear decommissioning trust assets | | 16,007 | 13,584 |
Emerging Market Bonds [Member] | Level 1 [Member] | | | |
Financial and Derivative Instruments and Trading Securities [Line Items] | | | |
Nuclear decommissioning trust assets | | 0 | 0 |
Emerging Market Bonds [Member] | Level 2 [Member] | | | |
Financial and Derivative Instruments and Trading Securities [Line Items] | | | |
Nuclear decommissioning trust assets | | 16,007 | 13,584 |
Emerging Market Bonds [Member] | Level 3 [Member] | | | |
Financial and Derivative Instruments and Trading Securities [Line Items] | | | |
Nuclear decommissioning trust assets | | 0 | 0 |
Combination Debt Equity And Other Fund [Member] | | | |
Financial and Derivative Instruments and Trading Securities [Line Items] | | | |
Nuclear decommissioning trust assets | | 12,816 | |
Combination Debt Equity And Other Fund [Member] | Level 1 [Member] | | | |
Financial and Derivative Instruments and Trading Securities [Line Items] | | | |
Nuclear decommissioning trust assets | | 0 | |
Combination Debt Equity And Other Fund [Member] | Level 2 [Member] | | | |
Financial and Derivative Instruments and Trading Securities [Line Items] | | | |
Nuclear decommissioning trust assets | | 12,816 | |
Combination Debt Equity And Other Fund [Member] | Level 3 [Member] | | | |
Financial and Derivative Instruments and Trading Securities [Line Items] | | | |
Nuclear decommissioning trust assets | | 0 | |
Combination Debt and Equity Fund [Member] | | | |
Financial and Derivative Instruments and Trading Securities [Line Items] | | | |
Nuclear decommissioning trust assets | | | 11,343 |
Combination Debt and Equity Fund [Member] | Level 1 [Member] | | | |
Financial and Derivative Instruments and Trading Securities [Line Items] | | | |
Nuclear decommissioning trust assets | | | 0 |
Combination Debt and Equity Fund [Member] | Level 2 [Member] | | | |
Financial and Derivative Instruments and Trading Securities [Line Items] | | | |
Nuclear decommissioning trust assets | | | 11,343 |
Combination Debt and Equity Fund [Member] | Level 3 [Member] | | | |
Financial and Derivative Instruments and Trading Securities [Line Items] | | | |
Nuclear decommissioning trust assets | | | 0 |
Alternative Funds [Member] | | | |
Financial and Derivative Instruments and Trading Securities [Line Items] | | | |
Nuclear decommissioning trust assets | | 17,886 | 16,439 |
Alternative Funds [Member] | Level 1 [Member] | | | |
Financial and Derivative Instruments and Trading Securities [Line Items] | | | |
Nuclear decommissioning trust assets | | 0 | 0 |
Alternative Funds [Member] | Level 2 [Member] | | | |
Financial and Derivative Instruments and Trading Securities [Line Items] | | | |
Nuclear decommissioning trust assets | | 0 | 0 |
Alternative Funds [Member] | Level 3 [Member] | | | |
Financial and Derivative Instruments and Trading Securities [Line Items] | | | |
Nuclear decommissioning trust assets | | 0 | 0 |
Real Estate Securities [Member] | | | |
Financial and Derivative Instruments and Trading Securities [Line Items] | | | |
Nuclear decommissioning trust assets | | 9,737 | 10,823 |
Real Estate Securities [Member] | Level 1 [Member] | | | |
Financial and Derivative Instruments and Trading Securities [Line Items] | | | |
Nuclear decommissioning trust assets | | 0 | 0 |
Real Estate Securities [Member] | Level 2 [Member] | | | |
Financial and Derivative Instruments and Trading Securities [Line Items] | | | |
Nuclear decommissioning trust assets | | 0 | 0 |
Real Estate Securities [Member] | Level 3 [Member] | | | |
Financial and Derivative Instruments and Trading Securities [Line Items] | | | |
Nuclear decommissioning trust assets | | 0 | 0 |
Cash Equivalents [Member] | | | |
Financial and Derivative Instruments and Trading Securities [Line Items] | | | |
Nuclear decommissioning trust assets | | 201 | 87 |
Trading securities | | | 159 |
Cash Equivalents [Member] | Level 1 [Member] | | | |
Financial and Derivative Instruments and Trading Securities [Line Items] | | | |
Nuclear decommissioning trust assets | | 201 | 87 |
Trading securities | | | 159 |
Cash Equivalents [Member] | Level 2 [Member] | | | |
Financial and Derivative Instruments and Trading Securities [Line Items] | | | |
Nuclear decommissioning trust assets | | 0 | 0 |
Trading securities | | | 0 |
Cash Equivalents [Member] | Level 3 [Member] | | | |
Financial and Derivative Instruments and Trading Securities [Line Items] | | | |
Nuclear decommissioning trust assets | | 0 | 0 |
Trading securities | | | 0 |
Portion at Other than Fair Value Measurement [Member] | | | |
Financial and Derivative Instruments and Trading Securities [Line Items] | | | |
Nuclear decommissioning trust assets | | 32,794 | 33,312 |
Trading securities | | 0 | 0 |
Total assets measured at fair value | | 32,794 | 33,312 |
Portion at Other than Fair Value Measurement [Member] | Domestic Equity [Member] | | | |
Financial and Derivative Instruments and Trading Securities [Line Items] | | | |
Nuclear decommissioning trust assets | | 5,171 | 6,050 |
Trading securities | | 0 | 0 |
Portion at Other than Fair Value Measurement [Member] | International Equity [Member] | | | |
Financial and Derivative Instruments and Trading Securities [Line Items] | | | |
Nuclear decommissioning trust assets | | 0 | 0 |
Trading securities | | 0 | 0 |
Portion at Other than Fair Value Measurement [Member] | Core Bonds [Member] | | | |
Financial and Derivative Instruments and Trading Securities [Line Items] | | | |
Nuclear decommissioning trust assets | | 0 | 0 |
Trading securities | | 0 | 0 |
Portion at Other than Fair Value Measurement [Member] | High-Yield Bonds [Member] | | | |
Financial and Derivative Instruments and Trading Securities [Line Items] | | | |
Nuclear decommissioning trust assets | | 0 | 0 |
Portion at Other than Fair Value Measurement [Member] | Emerging Market Bonds [Member] | | | |
Financial and Derivative Instruments and Trading Securities [Line Items] | | | |
Nuclear decommissioning trust assets | | 0 | 0 |
Portion at Other than Fair Value Measurement [Member] | Combination Debt Equity And Other Fund [Member] | | | |
Financial and Derivative Instruments and Trading Securities [Line Items] | | | |
Nuclear decommissioning trust assets | | 0 | |
Portion at Other than Fair Value Measurement [Member] | Combination Debt and Equity Fund [Member] | | | |
Financial and Derivative Instruments and Trading Securities [Line Items] | | | |
Nuclear decommissioning trust assets | | | 0 |
Portion at Other than Fair Value Measurement [Member] | Alternative Funds [Member] | | | |
Financial and Derivative Instruments and Trading Securities [Line Items] | | | |
Nuclear decommissioning trust assets | | 17,886 | 16,439 |
Portion at Other than Fair Value Measurement [Member] | Real Estate Securities [Member] | | | |
Financial and Derivative Instruments and Trading Securities [Line Items] | | | |
Nuclear decommissioning trust assets | | 9,737 | 10,823 |
Portion at Other than Fair Value Measurement [Member] | Cash Equivalents [Member] | | | |
Financial and Derivative Instruments and Trading Securities [Line Items] | | | |
Nuclear decommissioning trust assets | | $ 0 | 0 |
Trading securities | | | $ 0 |
| |
[1] | subject to the general partner’s right to extend the term for up to three additional one-year periods. | |