Summary of Significant Accounting Policies - Textual (Details) (USD $)	12 Months Ended												12 Months Ended											12 Months Ended												12 Months Ended							12 Months Ended																													12 Months Ended																										12 Months Ended								12 Months Ended			3 Months Ended				12 Months Ended										12 Months Ended																							12 Months Ended													12 Months Ended													12 Months Ended																							12 Months Ended	1 Months Ended	12 Months Ended									12 Months Ended																0 Months Ended						12 Months Ended		12 Months Ended									12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013 Maximum [Member]	Dec. 31, 2013 Plant Hatch [Member]	Dec. 31, 2013 Plant Vogtle [Member]	Dec. 31, 2013 Equity Securities [Member]	Dec. 31, 2012 Equity Securities [Member]	Dec. 31, 2013 Debt Securities [Member]	Dec. 31, 2012 Debt Securities [Member]	Dec. 31, 2013 Other Securities [Member]	Dec. 31, 2012 Other Securities [Member]	Dec. 31, 2013 Securities Held in Funds [Member] Realized Gain [Member]	Dec. 31, 2012 Securities Held in Funds [Member] Realized Gain [Member]	Dec. 31, 2011 Securities Held in Funds [Member] Realized Gain [Member]	Dec. 31, 2013 Securities Held in Funds [Member] Unrealized Gain [Member]	Dec. 31, 2012 Securities Held in Funds [Member] Unrealized Losses [Member]	Dec. 31, 2011 Securities Held in Funds [Member] Unrealized Losses [Member]	Dec. 31, 2013 Utility Plant in Service [Member]	Dec. 31, 2012 Utility Plant in Service [Member]	Dec. 31, 2011 Utility Plant in Service [Member]	Dec. 31, 2013 Other Plant in Service [Member]	Dec. 31, 2012 Other Plant in Service [Member]	Dec. 31, 2013 Other Plant in Service [Member] Minimum [Member]	Dec. 31, 2013 Other Plant in Service [Member] Maximum [Member]	Dec. 31, 2013 Recoverable Vacation Pay [Member]		Dec. 31, 2012 Recoverable Vacation Pay [Member]		Dec. 31, 2013 Retiree benefit plans [Member]		Dec. 31, 2012 Retiree benefit plans [Member]		Dec. 31, 2013 Other Postretirement Benefits [Member]	Dec. 31, 2012 Other Postretirement Benefits [Member]	Dec. 31, 2013 Southern Power [Member]	Dec. 31, 2012 Southern Power [Member]	Dec. 31, 2011 Southern Power [Member]	Dec. 31, 2013 Southern Power [Member] Minimum [Member]	Dec. 31, 2013 Southern Power [Member] Maximum [Member]	Dec. 31, 2013 Southern Power [Member] Southern Renewable Energy, Inc. [Member]	Dec. 31, 2013 Southern Power [Member] Turner Renewable Energy [Member]	Dec. 31, 2013 Southern Power [Member] Southern Company Services, Inc. [Member]	Dec. 31, 2012 Southern Power [Member] Southern Company Services, Inc. [Member]	Dec. 31, 2011 Southern Power [Member] Southern Company Services, Inc. [Member]	Dec. 31, 2013 Southern Power [Member] Operations and Maintenance Expense [Member] Southern Company Services, Inc. [Member]	Dec. 31, 2012 Southern Power [Member] Operations and Maintenance Expense [Member] Southern Company Services, Inc. [Member]	Dec. 31, 2011 Southern Power [Member] Operations and Maintenance Expense [Member] Southern Company Services, Inc. [Member]	Dec. 31, 2013 Southern Power [Member] Deferred capacity revenues affiliated [Member]	Dec. 31, 2012 Southern Power [Member] Deferred capacity revenues affiliated [Member]	Dec. 31, 2013 Southern Power [Member] Electric Transmission [Member] Southern Company Services, Inc. [Member]	Dec. 31, 2012 Southern Power [Member] Electric Transmission [Member] Southern Company Services, Inc. [Member]	Dec. 31, 2011 Southern Power [Member] Electric Transmission [Member] Southern Company Services, Inc. [Member]	Dec. 31, 2013 Southern Power [Member] Florida Power and Light [Member] Sales Revenue, Goods, Net [Member] Customer Concentration Risk [Member]	Dec. 31, 2012 Southern Power [Member] Florida Power and Light [Member] Sales Revenue, Goods, Net [Member] Customer Concentration Risk [Member]	Dec. 31, 2011 Southern Power [Member] Florida Power and Light [Member] Sales Revenue, Goods, Net [Member] Customer Concentration Risk [Member]	Dec. 31, 2011 Southern Power [Member] Progress Energy Carolina [Member] Sales Revenue, Goods, Net [Member] Customer Concentration Risk [Member]	Dec. 31, 2013 Southern Power [Member] Progress Energy Florida [Member] Sales Revenue, Goods, Net [Member] Customer Concentration Risk [Member]	Dec. 31, 2012 Southern Power [Member] Progress Energy Florida [Member] Sales Revenue, Goods, Net [Member] Customer Concentration Risk [Member]	Dec. 31, 2013 Southern Power [Member] Georgia Power [Member] Sales Revenue, Goods, Net [Member] Customer Concentration Risk [Member]	Dec. 31, 2012 Southern Power [Member] Georgia Power [Member] Sales Revenue, Goods, Net [Member] Customer Concentration Risk [Member]	Dec. 31, 2011 Southern Power [Member] Georgia Power [Member] Sales Revenue, Goods, Net [Member] Customer Concentration Risk [Member]	Dec. 31, 2013 Southern Power [Member] Operating Lease PPA [Member]	Dec. 31, 2012 Southern Power [Member] Operating Lease PPA [Member]	Dec. 31, 2011 Southern Power [Member] Operating Lease PPA [Member]	Dec. 31, 2013 Gulf Power [Member]	Dec. 31, 2012 Gulf Power [Member]	Dec. 31, 2011 Gulf Power [Member]	Dec. 31, 2013 Gulf Power [Member] Minimum [Member]	Dec. 31, 2013 Gulf Power [Member] Maximum [Member] kWh	Dec. 31, 2013 Gulf Power [Member] Plant Scherer Unit 3 [Member]	Dec. 31, 2013 Gulf Power [Member] Georgia Power [Member]	Dec. 31, 2012 Gulf Power [Member] Georgia Power [Member]	Dec. 31, 2011 Gulf Power [Member] Georgia Power [Member]	Dec. 31, 2013 Gulf Power [Member] Alabama Power [Member]	Dec. 31, 2012 Gulf Power [Member] Alabama Power [Member]	Dec. 31, 2011 Gulf Power [Member] Alabama Power [Member]	Dec. 31, 2013 Gulf Power [Member] Southern Power [Member] MW	Dec. 31, 2013 Gulf Power [Member] Southern Company Services, Inc. [Member]	Dec. 31, 2012 Gulf Power [Member] Southern Company Services, Inc. [Member]	Dec. 31, 2011 Gulf Power [Member] Southern Company Services, Inc. [Member]	Dec. 31, 2013 Gulf Power [Member] Mississippi Power [Member]	Dec. 31, 2012 Gulf Power [Member] Mississippi Power [Member]	Dec. 31, 2011 Gulf Power [Member] Mississippi Power [Member]	Dec. 31, 2013 Gulf Power [Member] Prepaid expenses and other regulatory liabilities [Member] Southern Power [Member]	Dec. 31, 2013 Gulf Power [Member] Current Liabilities [Member]	Dec. 31, 2012 Gulf Power [Member] Current Liabilities [Member]	Dec. 31, 2013 Gulf Power [Member] Deferred Credits and Other Liabilities [Member]	Dec. 31, 2012 Gulf Power [Member] Deferred Credits and Other Liabilities [Member]	Dec. 31, 2013 Gulf Power [Member] Recoverable Vacation Pay [Member]		Dec. 31, 2012 Gulf Power [Member] Recoverable Vacation Pay [Member]		Dec. 31, 2013 Gulf Power [Member] Retiree benefit plans [Member]		Dec. 31, 2012 Gulf Power [Member] Retiree benefit plans [Member]		Dec. 31, 2013 Gulf Power [Member] Fuel Expense [Member] Southern Power [Member]	Dec. 31, 2012 Gulf Power [Member] Fuel Expense [Member] Southern Power [Member]	Dec. 31, 2011 Gulf Power [Member] Fuel Expense [Member] Southern Power [Member]	Dec. 31, 2013 Gulf Power [Member] Purchased Power [Member] Southern Power [Member]	Dec. 31, 2012 Gulf Power [Member] Purchased Power [Member] Southern Power [Member]	Dec. 31, 2011 Gulf Power [Member] Purchased Power [Member] Southern Power [Member]	Dec. 31, 2013 Gulf Power [Member] Other Postretirement Benefits [Member]	Dec. 31, 2012 Gulf Power [Member] Other Postretirement Benefits [Member]	Dec. 31, 2013 Gulf Power [Member] Plant Scherer [Member]	Dec. 31, 2013 Gulf Power [Member] Plant Scherer [Member] Sales Agreement From Year Two Thousand Fifteen Till Two Thousand Twenty [Member]	Dec. 31, 2013 Gulf Power [Member] Plant Scherer [Member] Georgia Power [Member]	Sep. 30, 2013 Alabama Power [Member]	Mar. 31, 2013 Alabama Power [Member]	Mar. 31, 2012 Alabama Power [Member]	Sep. 30, 2011 Alabama Power [Member]	Dec. 31, 2013 Alabama Power [Member]	Dec. 31, 2012 Alabama Power [Member]	Dec. 31, 2011 Alabama Power [Member]	Dec. 31, 2013 Alabama Power [Member] SEGCO [Member]	Dec. 31, 2013 Alabama Power [Member] Equity Securities [Member]	Dec. 31, 2012 Alabama Power [Member] Equity Securities [Member]	Dec. 31, 2013 Alabama Power [Member] Debt Securities [Member]	Dec. 31, 2012 Alabama Power [Member] Debt Securities [Member]	Dec. 31, 2013 Alabama Power [Member] Other Securities [Member]	Dec. 31, 2012 Alabama Power [Member] Other Securities [Member]	Dec. 31, 2012 Alabama Power [Member] Securities Held in Funds [Member]	Dec. 31, 2011 Alabama Power [Member] Securities Held in Funds [Member]	Dec. 31, 2013 Alabama Power [Member] Securities Held in Funds [Member] Realized Gain [Member]	Dec. 31, 2012 Alabama Power [Member] Securities Held in Funds [Member] Realized Gain [Member]	Dec. 31, 2011 Alabama Power [Member] Securities Held in Funds [Member] Realized Gain [Member]	Dec. 31, 2013 Alabama Power [Member] Securities Held in Funds [Member] Unrealized Gain [Member]	Dec. 31, 2013 Alabama Power [Member] Utility Plant in Service [Member]	Dec. 31, 2012 Alabama Power [Member] Utility Plant in Service [Member]	Dec. 31, 2011 Alabama Power [Member] Utility Plant in Service [Member]	Dec. 31, 2013 Alabama Power [Member] Southern Company Services, Inc. [Member]	Dec. 31, 2012 Alabama Power [Member] Southern Company Services, Inc. [Member]	Dec. 31, 2011 Alabama Power [Member] Southern Company Services, Inc. [Member]	Dec. 31, 2013 Alabama Power [Member] Southern Nuclear Operating Company, Inc. [Member]	Dec. 31, 2012 Alabama Power [Member] Southern Nuclear Operating Company, Inc. [Member]	Dec. 31, 2011 Alabama Power [Member] Southern Nuclear Operating Company, Inc. [Member]	Dec. 31, 2013 Alabama Power [Member] Gulf Power [Member]	Dec. 31, 2013 Alabama Power [Member] Recoverable Vacation Pay [Member]		Dec. 31, 2012 Alabama Power [Member] Recoverable Vacation Pay [Member]		Dec. 31, 2013 Alabama Power [Member] Other Postretirement Benefits [Member]	Dec. 31, 2012 Alabama Power [Member] Other Postretirement Benefits [Member]	Dec. 31, 2013 Alabama Power [Member] Plant Farley [Member]	Dec. 31, 2013 Alabama Power [Member] Fuel Purchases [Member] Mississippi Power [Member]	Dec. 31, 2012 Alabama Power [Member] Fuel Purchases [Member] Mississippi Power [Member]	Dec. 31, 2011 Alabama Power [Member] Fuel Purchases [Member] Mississippi Power [Member]	Dec. 31, 2013 Alabama Power [Member] Non-Fuel Expense [Member] Mississippi Power [Member]	Dec. 31, 2012 Alabama Power [Member] Non-Fuel Expense [Member] Mississippi Power [Member]	Dec. 31, 2011 Alabama Power [Member] Non-Fuel Expense [Member] Mississippi Power [Member]	Dec. 31, 2013 Georgia Power [Member]	Dec. 31, 2012 Georgia Power [Member]	Dec. 31, 2011 Georgia Power [Member]	Dec. 31, 2013 Georgia Power [Member] Unrealized Losses [Member]	Dec. 31, 2012 Georgia Power [Member] Unrealized Losses [Member]	Dec. 31, 2011 Georgia Power [Member] Unrealized Losses [Member]	Dec. 31, 2013 Georgia Power [Member] Plant Scherer Unit 3 [Member]	Dec. 31, 2013 Georgia Power [Member] Plant McIntosh [Member]	Dec. 31, 2013 Georgia Power [Member] Plant Hatch [Member]	Dec. 31, 2012 Georgia Power [Member] Plant Hatch [Member]	Dec. 31, 2013 Georgia Power [Member] Plant Vogtle [Member]	Dec. 31, 2013 Georgia Power [Member] Securities Investment [Member]	Dec. 31, 2012 Georgia Power [Member] Securities Investment [Member]	Dec. 31, 2011 Georgia Power [Member] Securities Investment [Member]	Dec. 31, 2013 Georgia Power [Member] Equity Securities [Member]	Dec. 31, 2012 Georgia Power [Member] Equity Securities [Member]	Dec. 31, 2013 Georgia Power [Member] Debt Securities [Member]	Dec. 31, 2012 Georgia Power [Member] Debt Securities [Member]	Dec. 31, 2013 Georgia Power [Member] Other Securities [Member]	Dec. 31, 2012 Georgia Power [Member] Other Securities [Member]	Dec. 31, 2013 Georgia Power [Member] Southern Power [Member]	Dec. 31, 2012 Georgia Power [Member] Southern Power [Member]	Dec. 31, 2011 Georgia Power [Member] Southern Power [Member]	Dec. 31, 2013 Georgia Power [Member] Southern Company Services, Inc. [Member]	Dec. 31, 2012 Georgia Power [Member] Southern Company Services, Inc. [Member]	Dec. 31, 2011 Georgia Power [Member] Southern Company Services, Inc. [Member]	Dec. 31, 2013 Georgia Power [Member] Southern Nuclear Operating Company, Inc. [Member]	Dec. 31, 2012 Georgia Power [Member] Southern Nuclear Operating Company, Inc. [Member]	Dec. 31, 2011 Georgia Power [Member] Southern Nuclear Operating Company, Inc. [Member]	Dec. 31, 2013 Georgia Power [Member] Gulf Power [Member] Plant Scherer Unit 3 [Member]	Dec. 31, 2013 Georgia Power [Member] Other regulatory assets current [Member]	Dec. 31, 2013 Georgia Power [Member] Other regulatory assets deferred [Member]	Dec. 31, 2013 Georgia Power [Member] Recoverable Vacation Pay [Member]		Dec. 31, 2012 Georgia Power [Member] Recoverable Vacation Pay [Member]		Dec. 31, 2013 Georgia Power [Member] Retiree benefit plans [Member]		Dec. 31, 2012 Georgia Power [Member] Retiree benefit plans [Member]		Dec. 31, 2013 Georgia Power [Member] Storm damage [Member]	Dec. 31, 2013 Georgia Power [Member] Other Postretirement Benefits [Member]	Dec. 31, 2012 Georgia Power [Member] Other Postretirement Benefits [Member]	Dec. 31, 2011 Georgia Power [Member] Storm reserve [Member]	Dec. 31, 2013 Georgia Power [Member] Environmental remediation reserve [Member]	Dec. 31, 2013 Georgia Power [Member] Environmental remediation reserve [Member]	Dec. 31, 2013 Georgia Power [Member] Non-Fuel Expense [Member] Gulf Power [Member] Plant Scherer Unit 3 [Member]	Dec. 31, 2012 Georgia Power [Member] Non-Fuel Expense [Member] Gulf Power [Member] Plant Scherer Unit 3 [Member]	Dec. 31, 2011 Georgia Power [Member] Non-Fuel Expense [Member] Gulf Power [Member] Plant Scherer Unit 3 [Member]	Dec. 31, 2013 Alabama Power and Georgia Power [Member]	Dec. 31, 2013 Mississippi Power [Member]	Dec. 31, 2012 Mississippi Power [Member]	Dec. 31, 2011 Mississippi Power [Member]	Jun. 04, 2013 Mississippi Power [Member]	Dec. 31, 2013 Mississippi Power [Member] Southern Company Services, Inc. [Member]	Dec. 31, 2012 Mississippi Power [Member] Southern Company Services, Inc. [Member]	Dec. 31, 2011 Mississippi Power [Member] Southern Company Services, Inc. [Member]	Dec. 31, 2013 Mississippi Power [Member] Gulf Power [Member]	Dec. 31, 2012 Mississippi Power [Member] Gulf Power [Member]	Dec. 31, 2011 Mississippi Power [Member] Gulf Power [Member]	Dec. 31, 2013 Mississippi Power [Member] Property tax [Member]		Dec. 31, 2012 Mississippi Power [Member] Property tax [Member]		Dec. 31, 2013 Mississippi Power [Member] Recoverable Vacation Pay [Member]		Dec. 31, 2012 Mississippi Power [Member] Recoverable Vacation Pay [Member]		Dec. 31, 2013 Mississippi Power [Member] Other Postretirement Benefits [Member]	Dec. 31, 2012 Mississippi Power [Member] Other Postretirement Benefits [Member]	Oct. 20, 2011 Mississippi Power [Member] Plant Daniel Units 3 and 4 [Member]	Dec. 31, 2013 Mississippi Power [Member] Plant Daniel Units 3 and 4 [Member]		Dec. 31, 2012 Mississippi Power [Member] Plant Daniel Units 3 and 4 [Member]		Dec. 31, 2011 Mississippi Power [Member] Plant Daniel Units 3 and 4 [Member]	Dec. 31, 2013 Mississippi Power [Member] Kemper IGCC [Member]	Dec. 31, 2010 Mississippi Power [Member] Kemper IGCC [Member]	Dec. 31, 2013 Mississippi Power [Member] Fuel Purchases [Member] Alabama Power [Member]	Dec. 31, 2012 Mississippi Power [Member] Fuel Purchases [Member] Alabama Power [Member]	Dec. 31, 2011 Mississippi Power [Member] Fuel Purchases [Member] Alabama Power [Member]	Dec. 31, 2013 Mississippi Power [Member] Non-Fuel Expense [Member] Alabama Power [Member]	Dec. 31, 2012 Mississippi Power [Member] Non-Fuel Expense [Member] Alabama Power [Member]	Dec. 31, 2011 Mississippi Power [Member] Non-Fuel Expense [Member] Alabama Power [Member]	Dec. 31, 2012 Mississippi Power [Member] Storm Assistance [Member] Traditional Operating Companies [Member]	Dec. 31, 2013 Traditional Operating Companies [Member]	Dec. 31, 2012 Traditional Operating Companies [Member]	Dec. 31, 2013 Capital Lease Obligations [Member]	Dec. 31, 2012 Capital Lease Obligations [Member]	Dec. 31, 2011 Capital Lease Obligations [Member]	Dec. 31, 2013 Capital Lease Obligations [Member] Georgia Power [Member]	Dec. 31, 2012 Capital Lease Obligations [Member] Georgia Power [Member]	Dec. 31, 2013 Capital Lease Obligations [Member] Mississippi Power [Member]
Jointly Owned Utility Plant Interests [Abstract]
Jointly Owned Utility Plant, Proportionate Ownership Share																																									90.00%	10.00%																													25.00%																																										14.00%			86.00%																																										75.00%
Affiliate Transactions [Abstract]
Affiliate transaction amount																																				$ 148,400,000	$ 159,900,000	$ 175,900,000					$ 117,600,000	$ 125,400,000	$ 112,700,000	$ 114,300,000	$ 107,700,000	$ 87,900,000	$ 17,600,000	$ 19,000,000	$ 8,300,000	$ 6,600,000	$ 7,100,000										$ 69,000,000	$ 76,200,000	$ 75,600,000							$ 10,200,000	$ 6,900,000	$ 6,700,000					$ 78,400,000	$ 95,900,000	$ 97,400,000	$ 16,500,000	$ 21,100,000	$ 23,400,000														$ 800,000	$ 2,600,000	$ 1,800,000	$ 14,200,000	$ 14,700,000	$ 14,300,000																													$ 340,000,000	$ 340,000,000	$ 347,000,000	$ 211,000,000	$ 218,000,000	$ 215,000,000									$ 27,000,000	$ 28,000,000	$ 21,000,000	$ 13,000,000	$ 12,000,000	$ 12,000,000																					$ 136,000,000	$ 147,000,000	$ 171,000,000	$ 504,000,000	$ 540,000,000	$ 550,000,000	$ 555,000,000	$ 574,000,000	$ 537,000,000																										$ 205,000,000	$ 212,700,000	$ 185,500,000	$ 16,500,000	$ 21,200,000	$ 23,300,000																			$ 27,100,000	$ 28,100,000	$ 20,900,000	$ 12,500,000	$ 11,700,000	$ 12,200,000	$ 2,000,000
Long-term Purchase Commitment, Period Over Which Costs Are Expected to Be Recovered																																																																																																																																										2023
Long-term Purchase Commitment, Minimum Power Required																																																																														292
Gulf Power agreement, commitment amount																																																																																																																																										22,000,000
Long-Term Purchase Commitment Amount In Year Two																																																																																																																																										31,000,000
Prepaid capacity expenses																																																																																																																																																																												15,000,000
Gulf Power agreement, percentage reimbursement of non-fuel expenses																																																																																																																																																																																					25.00%
Deferred capacity expense																																																																		180,149,000	137,568,000											4,200,000							4,200,000																																																																			162,000,000	169,000,000	216,000,000
Gulf Power agreement, reimbursement of non-fuel expenses																																																																								2,400,000	2,400,000	2,400,000																																																																																																																												10,000,000	7,000,000	7,000,000
Revenue Requirement Obligations																																																																											135,000,000
Revenue Requirements Reimbursement																																																																											7,900,000	3,000,000
Strom restoration cost																																																																													1,400,000
Government Grants [Abstract]
Grants expected to be received from Department of Energy																																																																																																																																																																																																																																				25,000,000	270,000,000
Grants received from Department of Energy																																																																																																																																																																																																																																				245,300,000
Revenues [Abstract]
Percentage Of Wholesale Customers To Operating Revenue																																																																																																																																																																																																										22.20%
Period Of Contract Cancellation Notices Of Wholesale Customers																																																																																																																																																																																																										10 years
Projected fuel cost over or under recovery threshold, as a percentage of projected fuel revenue																																																																		10.00%			10.00%
Percent Of Long-Term Sales Agreements																																																																																																											57.00%	100.00%
Period For Long-Term Sales Agreement Two																																																																																																										5 years
Period For Long-Term Sales Agreement One																																																																																																										2 years
Maximum revenue from a single customer or industry	10.00%																																																					11.80%	12.80%	14.70%	8.30%	10.30%	5.90%	10.70%	12.50%	14.00%				10.00%																																															10.00%																																							10.00%																																																		10.00%
Maximum percentage of uncollectible accounts	1.00%																																																																	1.00%																																															1.00%																																							1.00%																																																		1.00%
Property, Plant and Equipment [Abstract]
Refueling cycles for Alabama Power and Georgia Power, minimum months																																																																																																																	18 months																																							18 months																																																	18 months
Refueling cycles for Alabama Power and Georgia Power, maximum months																																																																																																																																																								24 months																																																	24 months
Amortization period of defer inspection costs for the combustion turbines																																																																																																																																																															10 years
Amortization Period of Defer Costs of Certain Significant Inspection Costs for Combustion Turbines																																																																																																																																																															10 years
Non-cash property additions recognized	411,000,000	524,000,000	929,000,000																																																																																																																																																																																																																																												107,000,000	14,000,000	21,000,000
Nuclear outage expense																																																																																																													32,000,000	28,000,000	31,000,000	38,000,000	31,000,000
Unamortized Nuclear Outage Expense																																																																																																																	51,000,000
Revenue bond obligations fair value																																																																																																																																																																																																																														346,100,000
Cash payment to be made in conjunction with purchase of facility																																																																																																																																																																																																																														84,800,000					85,000,000
Face value of debt obligations assumed																																																																																																																																																																																																																														270,000,000
Fixed stated interest rate of debt obligation																																																																																																																																																																																																										9.932%	9.967%	7.13%																		7.13%																				7.90%	7.90%	4.90%
Income Tax Matters [Abstract]
Amortization of deferred investment tax credits	16,000,000	23,000,000	19,000,000																																																															1,400,000	1,400,000	1,300,000																																													8,000,000	8,000,000	8,000,000																																					5,000,000	13,000,000	9,000,000																																																1,200,000	1,200,000	1,300,000
Credits amortized to income tax expense	5,500,000	2,600,000																																		5,500,000	2,600,000
Reduction in tax basis of assets																																				50.00%
Depreciation and Amortization
Depreciation of cost of utility plant in service, composite straight-line rate																			3.30%	3.20%	3.20%																																													3.60%	3.60%	3.50%																																																													3.20%	3.20%	3.30%																					3.00%	2.90%	2.80%																																																3.40%	3.50%	3.90%
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	23,059,000,000	21,964,000,000																	22,500,000,000	21,500,000,000		513,000,000	479,000,000													871,963,000	786,620,000																													1,211,336,000	1,168,055,000																																														8,114,000,000	7,761,000,000																																						10,970,000,000	10,431,000,000																																																	1,095,352,000	1,065,474,000
Regulatory liabilities amortized																																																																																																																																																								31,000,000		31,000,000
Amortization period of other cost of removal obligations																																																																																																																																																								3 years
Additional Regulatory Liability Amortization																																																																																																																																																								43,000,000
Plant in service, estimated useful lives																								3 years	25 years														18 years	34 years
Plant acquisition adjustment	123,000,000	124,000,000																																																																2,031,000	2,286,000				2,000,000																																										12,000,000	12,000,000																																						28,000,000	28,000,000																																																	81,412,000	81,412,000																			81,400,000
Fair value adjustment at date of purchase																																																																																																																																																																																																																														76,051,000					76,100,000
Fair value adjustment at date of purchase, amortization term																																																																																																																																																																																																																														10 years
Amortization period of regulatory assets and liabilities																																																																																																																																																																																																										50 years										12 months										10 years
Impairment of Long-Lived Assets and Intangibles
Average term of PPAs																																				20 years
Deferred Project Development Costs
Deferred project development costs																																				11,200,000	11,200,000
Decommissioning
Estimated cost of decommissioning completion year					2068	2072																																																																																																																																											2076															2068		2072
Minimum net worth requirement by a one or more persons to hold external trust funds	100,000,000																																																																																																																100,000,000																																							100,000,000
Fair market value of fund's securities on loan under the Funds' managers' securities lending program																																																																																																																																																								32,000,000	91,000,000
Fair value of collateral received																																																																																																																																																								33,000,000	93,000,000
Decommissioning Fund Investments Net Of Foreign Currency																																																																																																																	713,000,000	604,000,000																																						751,000,000	698,000,000
Investment securities in the Funds	1,465,000,000	1,303,000,000					896,000,000	718,000,000	528,000,000	564,000,000	40,000,000	20,000,000																																																																																																					714,000,000	605,000,000			566,000,000	438,000,000	131,000,000	156,000,000	16,000,000	10,000,000																														751,000,000	698,000,000										705,000,000	850,000,000	1,800,000,000	330,000,000	280,000,000	397,000,000	408,000,000	24,000,000	10,000,000
Proceeds from sale of securities held in external trust funds	1,000,000,000	1,000,000,000	2,200,000,000																																																																																																														279,000,000	193,000,000	349,000,000
Increase (Decrease) in fair value of securities related to nuclear decommissioning	181,000,000	137,000,000	29,000,000										5,000,000	4,000,000	41,000,000	119,000,000	75,000,000	60,000,000																																																																																															120,000,000	70,000,000	6,000,000								50,000,000	51,000,000	5,000,000	4,000,000	41,000,000	85,000,000																								61,000,000	67,000,000	23,000,000	34,000,000	25,000,000	9,000,000
Amount expensed for rate making purpose					2,000,000																																																																																																																																																											4,000,000	2,000,000	2,000,000
Significant assumption of inflation rate used to determine the costs for rate making																																																																																																																	4.50%																																							2.40%
Significant assumption of trust earnings rate used to determine the costs for rate making																																																																																																																	7.00%																																							4.40%
Allowance for Funds Used During Construction and Interest Capitalized
Composite rate used to determine allowance for funds used during construction																																																																		6.26%	6.72%	7.65%																																													9.10%	9.40%	9.20%																																					5.30%	6.80%	7.50%																																																6.89%	7.04%	7.06%
AFUDC capitalized																																																																																																																																																								44,000,000	75,000,000	134,000,000
AFUDC, net of income taxes	15.00%	8.20%	9.10%																																																															6.87%	5.36%	11.75%																																													5.40%	3.30%	3.90%																																					3.30%	5.70%	10.40%
Cash payments for interest totaled	759,000,000	803,000,000	832,000,000																																	60,396,000	50,248,000	74,989,000																												53,401,000	58,255,000	55,486,000																																													243,000,000	273,000,000	286,000,000																																					344,000,000	337,000,000	346,000,000																																																20,285,000	32,589,000	14,814,000
Net of amounts capitalized	92,000,000	83,000,000	78,000,000																																	9,178,000	19,092,000	18,001,000																												3,421,000	2,500,000	3,951,000																																													11,000,000	7,000,000	9,000,000																																					14,000,000	21,000,000	37,000,000																																																54,118,000	32,816,000	10,065,000
Reserves and Recoveries
Accrued reserves																																																																		35,400,000	32,000,000																																																																																																																																																																										28,000,000	28,000,000
Recovery Period For Natural Disaster Reserve Costs																																																																		60 days																																															24 months
Customer Surcharge Storm Recovery Costs																																																																						4
Customer Surcharge Storm Recovery Capacity																																																																						1,000
Maximum total rate NDR charge per month, non-residential customer account																																																																																																																	10
Maximum total rate NDR charge per month, residential customer account																																																																																																																	5
Old Natural Disaster Reserve Authorized Limit																																																																																																																	75,000,000
Costs recovered annually under rate plan																																																																																																																																																																																																			18,000,000	2,000,000	3,000,000
Environmental Exit Costs, Assets Previously Disposed, Liability for Remediation																																																																		50,400,000																																																																																						18,000,000
Environmental Regulatory Assets																																																																																																																																																																																						2,000,000	9,000,000
PSC Approved Annual Property Damage Reserve Accrual																																																																		3,500,000																																																																																																																																											3,200,000
PSC approved target level for property damage reserve																																																																					48,000,000	55,000,000
Threshold above which additional property damage reserves are authorized by PSC																																																																		3,500,000
Increase in accrued property damage costs																																																																		3,500,000	3,500,000	3,500,000
Cumulative damage costs limit under PSC order																																																																		100,000,000
PSC approved annual uninsured injuries and damages accrual																																																																		1,600,000				2,000,000.0
Threshold above which additional uninsured injuries and damages accruals are authorized by PSC																																																																		1,600,000
Reserve for losses and loss adjustment expenses																																																																		3,600,000	3,100,000																			1,600,000	1,600,000	2,000,000	1,500,000
Net Regulatory Assets	2,624,000,000	4,322,000,000																								171,000,000	[1],[2]	165,000,000	[1],[2]	1,760,000,000	[1],[3]	3,373,000,000	[1],[3]																																	160,224,000	171,985,000																							9,521,000	[1],[2]	9,238,000	[1],[2]	68,296,000	[1],[3]	141,429,000	[1],[3]																92,000,000	703,000,000																									63,000,000	[1],[2]	61,000,000	[1],[2]										1,886,000,000	2,471,000,000																															88,000,000	[1],[2]	85,000,000	[1],[2]	691,000,000	[1],[4]	1,331,000,000	[1],[4]											66,604,000	147,469,000									31,206,000	[5]	27,882,000	[5]	10,214,000	[1],[2]	9,635,000	[1],[2]	2,116,000	15,454,000		18,821,000	[6]	12,386,000	[6]
Threshold above which actual damages are charged to the reserve																																																																																																																																																																																																										50,000
Retail accrual per annual SRR rate																																																																																																																																																																																																										3,200,000	3,500,000	3,800,000
Wholesale accrual per annual SRR rate																																																																																																																																																																																																										300,000	300,000	300,000
Regulatory asset																																																																																																																																																																																																37,000,000
Other Regulatory Assets Current	124,000,000	163,000,000																																																																18,536,000	30,576,000																																														7,000,000	24,000,000																																						66,000,000	72,000,000																																							30,000,000										52,496,000	55,302,000
Other Regulatory Assets Deferred	2,557,000,000	4,032,000,000																																109,000,000	360,000,000																															340,415,000	372,294,000																																					0	2,169,000								692,000,000	1,083,000,000																													6,000,000	89,000,000								1,152,000,000	1,798,000,000																																							7,000,000	69,000,000	187,000,000								200,620,000	236,225,000																	5,227,000	15,454,000
Accrual Under Alternate Rate Plan																																																																																																																																																								30,000,000
Leveraged Leases [Abstract]
Leveraged lease agreement term				45 years
Cash and Cash Equivalents [Abstract]
Original Maturities of Temporary Cash Investments	90 days																																			90 days																														90 days																																																																																						90 days																																																		90 days
Variable Interest Entities [Abstract]
Variable Interest Entity, Consolidated, Carrying Amount, Assets																																																																																																																																																																																																										21,000,000	21,000,000
Variable Interest Entity, Consolidated, Carrying Amount, Liabilities																																																																																																																																																																																																										$ 22,700,000	$ 21,800,000

[1] Not earning a return as offset in rate base by a corresponding asset or liability.

[2] Recorded as earned by employees and recovered as paid, generally within one year. This includes both vacation and banked holiday pay.

[3] Recovered and amortized over the average remaining service period which may range up to 15 years. See Note 2 for additional information.

[4] Recovered and amortized over the average remaining service period which may range up to 14 years. See Note 2 for additional information.

[5] Recovered through the ad valorem tax adjustment clause over a 12-month period beginning in April of the following year. See Note 3 under "Ad Valorem Tax Adjustment" for additional information.

[6] Deferred and amortized over a 10-year period beginning October 2021, as approved by the Mississippi PSC for the difference between the revenue requirement under the purchase option and the revenue requirement assuming operating lease accounting treatment for the extended term.