Financial Instruments And Investments (Fair Values Of Long-Term Debt And Financing Obligations) (Details) (USD $) In Thousands	Sep. 30, 2011		Dec. 31, 2010
Carrying Amount	$ 867,577		$ 854,449
Estimated Fair Value	944,070		882,699
Pollution Control Bonds [Member]
Carrying Amount	193,135		193,135
Estimated Fair Value	207,552		192,924
RGRT Senior Notes [Member]
Carrying Amount	110,000	[1]	110,000	[1]
Estimated Fair Value	115,235	[1]	110,371	[1]
Senior Notes [Member]
Carrying Amount	546,649		546,610
Estimated Fair Value	603,490		574,700
Revolving Credit Facility [Member]
Carrying Amount	17,793	[1]	4,704	[1]
Estimated Fair Value	$ 17,793	[1]	$ 4,704	[1]

[1] Nuclear fuel financing as of September 30, 2011 is funded through the $110.0 million RGRT Senior Notes and $17.8 million under the RCF. The interest rate on the Company’s borrowings under the RCF is reset throughout the quarter reflecting current market rates. Consequently, the carrying value approximates fair value.