Regulatory Assets and Liabilities (Details) (USD $) In Thousands, unless otherwise specified															9 Months Ended			9 Months Ended									9 Months Ended									9 Months Ended
	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2014 Accumulated Retirement Costs Other Obligation [Member]	Dec. 31, 2013 Accumulated Retirement Costs Other Obligation [Member]	Sep. 30, 2014 Deferred Effects On Net Margin For Energy Facilities [Member] Hawk Road [Member]	Dec. 31, 2013 Deferred Effects On Net Margin For Energy Facilities [Member] Hawk Road [Member]	Sep. 30, 2014 Major Maintenance Sinking Fund [Member]	Dec. 31, 2013 Major Maintenance Sinking Fund [Member]	Sep. 30, 2014 Deferred Debt Service Adder [Member]	Dec. 31, 2013 Deferred Debt Service Adder [Member]	Sep. 30, 2014 Asset Retirement Obligation Costs [Member]	Dec. 31, 2013 Asset Retirement Obligation Costs [Member]	Sep. 30, 2014 Other Regulatory Liabilities [Member]	Dec. 31, 2013 Other Regulatory Liabilities [Member]	Sep. 30, 2014 Other Regulatory Liabilities [Member] Maximum	Sep. 30, 2014 Premium And Loss On Reacquired Debt [Member]	Dec. 31, 2013 Premium And Loss On Reacquired Debt [Member]	Sep. 30, 2014 Premium And Loss On Reacquired Debt [Member] Maximum	Sep. 30, 2014 Amortization Of Capital Leases [Member]	Dec. 31, 2013 Amortization Of Capital Leases [Member]	Sep. 30, 2014 Unamortized Deferred Outage Costs Net [Member]	Dec. 31, 2013 Unamortized Deferred Outage Costs Net [Member]	Sep. 30, 2014 Unamortized Deferred Interest Rate Swap Termination Fees [Member]	Dec. 31, 2013 Unamortized Deferred Interest Rate Swap Termination Fees [Member]	Sep. 30, 2014 Unamortized Deferred Depreciation Expense [Member]	Dec. 31, 2013 Unamortized Deferred Depreciation Expense [Member]	Sep. 30, 2014 Unamortized Deferred Depreciation Expense [Member] Plant Vogtle [Member]	Sep. 30, 2014 Deferred Training Costs V3 V4 [Member] Vogtle Units Number3 And Number4	Dec. 31, 2013 Deferred Training Costs V3 V4 [Member] Vogtle Units Number3 And Number4	Sep. 30, 2014 Interest Rate Option Cost [Member]	Dec. 31, 2013 Interest Rate Option Cost [Member]	Sep. 30, 2014 Deferred Effect On Net Margin For Energy Facilities [Member] Smith [Member]	Dec. 31, 2013 Deferred Effect On Net Margin For Energy Facilities [Member] Smith [Member]	Sep. 30, 2014 Other Regulatory Assets [Member]	Dec. 31, 2013 Other Regulatory Assets [Member]	Sep. 30, 2014 Other Regulatory Assets [Member] Maximum	Sep. 30, 2014 Unamortized Deferred Coal Fired Outage Costs Net [Member] Minimum	Sep. 30, 2014 Unamortized Deferred Coal Fired Outage Costs Net [Member] Maximum	Sep. 30, 2014 Unamortized Deferred Nuclear Refueling Outage Costs Net [Member] Minimum	Sep. 30, 2014 Unamortized Deferred Nuclear Refueling Outage Costs Net [Member] Maximum
Regulatory assets and liabilities
Total Regulatory Assets	$ 412,456	$ 331,108														$ 74,415	$ 82,499		$ 11,897	$ 16,124	$ 44,911	$ 35,155	$ 10,343	$ 13,336	$ 47,294	$ 48,362		$ 31,126	$ 27,678	$ 89,781	$ 38,984	$ 96,811	$ 63,491	$ 5,878	$ 5,479
Total Regulatory Liabilities	167,250	158,789	21,069	24,520	28,605	23,379	26,762	28,064	64,375	57,223	21,508	19,508	4,931	6,095
Net Regulatory Assets	$ 245,206	$ 172,319
Amortization period																		30 years																		35 years	18 months	36 months	18 months	24 months
Operating license expected extension period for Plant Vogtle																											20 years
Operating license, expected extension period, for Plant Vogtle																											40 years
Amortization period															18 years