Financial Instruments And Investments (Long-Term Debt and Short-Term Borrowings - Narratives) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Dec. 31, 2015
Financial Instruments and Investments [Line Items]
Decommissioning Fund Investments	$ 243,690	$ 239,035
Accounting Standards Update 2015-03
Financial Instruments and Investments [Line Items]
Amounts previously reported, reclassified	11,600
Nuclear Fuel Financing
Financial Instruments and Investments [Line Items]
Line of Credit Facility, Amount Outstanding	37,100	33,700
Working Capital and General Purpose
Financial Instruments and Investments [Line Items]
Line of Credit Facility, Amount Outstanding	50,000	108,000
RGRT Senior Notes
Financial Instruments and Investments [Line Items]
Long-term Debt, Gross	$ 95,000	$ 95,000