Risk Management and Fair Values (Assets And Liabilities At Fair Value On A Recurring Basis) (Details) - USD ($)		Mar. 31, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash Equivalents, at Carrying Value		$ 865,112,000	$ 424,285,000
Assets at fair value on a recurring basis
Restricted Cash and Cash Equivalents, Current		52,000,000	51,000,000
Replacement Reserve Escrow		405,000,000	403,000,000
Equity Securities, FV-NI		1,357,000,000	1,686,000,000
Debt Securities		2,992,000,000	2,884,000,000
Liabilities at fair value on a recurring basis
Assets, Fair Value Disclosure		8,209,000,000	7,818,000,000
Financial and Nonfinancial Liabilities, Fair Value Disclosure		50,000,000	35,000,000
Gas Hedge Contracts [Member]
Liabilities at fair value on a recurring basis
Liabilities, Fair Value Disclosure on Recurring Basis		1,000,000	1,000,000
Power Contracts Liabilities [Member]
Liabilities at fair value on a recurring basis
Liabilities, Fair Value Disclosure on Recurring Basis		49,000,000	34,000,000
Common trust funds valued using Net Asset Value [Domain]
Assets at fair value on a recurring basis
Available-for-sale Securities		2,529,000,000	2,350,000,000
Power Contracts Assets [Member]
Assets at fair value on a recurring basis
Derivative Asset		3,000,000	3,000,000
Gas Hedge Contracts Assets [Member]
Assets at fair value on a recurring basis
Derivative Asset		1,000,000
Fixed Transmission Rights (FTRs) [Member]
Assets at fair value on a recurring basis
Derivative Asset		5,000,000	15,000,000
Fair Value Inputs Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash Equivalents, at Carrying Value		865,000,000	424,000,000
Assets at fair value on a recurring basis
Restricted Cash and Cash Equivalents, Current		52,000,000	51,000,000
Replacement Reserve Escrow		405,000,000	403,000,000
Equity Securities, FV-NI		1,357,000,000	1,686,000,000
Debt Securities		1,320,000,000	1,259,000,000
Liabilities at fair value on a recurring basis
Assets, Fair Value Disclosure		4,000,000,000	3,823,000,000
Financial and Nonfinancial Liabilities, Fair Value Disclosure		1,000,000	1,000,000
Fair Value Inputs Level 1 [Member] | Gas Hedge Contracts [Member]
Liabilities at fair value on a recurring basis
Liabilities, Fair Value Disclosure on Recurring Basis		1,000,000	1,000,000
Fair Value Inputs Level 1 [Member] | Power Contracts Liabilities [Member]
Liabilities at fair value on a recurring basis
Liabilities, Fair Value Disclosure on Recurring Basis		0	0
Fair Value Inputs Level 1 [Member] | Power Contracts Assets [Member]
Assets at fair value on a recurring basis
Derivative Asset		0	0
Fair Value Inputs Level 1 [Member] | Gas Hedge Contracts Assets [Member]
Assets at fair value on a recurring basis
Derivative Asset		1,000,000
Fair Value Inputs Level 1 [Member] | Fixed Transmission Rights (FTRs) [Member]
Assets at fair value on a recurring basis
Derivative Asset		0	0
Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash Equivalents, at Carrying Value		0	0
Assets at fair value on a recurring basis
Restricted Cash and Cash Equivalents, Current		0	0
Replacement Reserve Escrow		0	0
Equity Securities, FV-NI		0	0
Debt Securities		1,672,000,000	1,625,000,000
Liabilities at fair value on a recurring basis
Assets, Fair Value Disclosure		1,672,000,000	1,627,000,000
Financial and Nonfinancial Liabilities, Fair Value Disclosure		0	0
Fair Value, Inputs, Level 2 [Member] | Gas Hedge Contracts [Member]
Liabilities at fair value on a recurring basis
Liabilities, Fair Value Disclosure on Recurring Basis		0	0
Fair Value, Inputs, Level 2 [Member] | Power Contracts Liabilities [Member]
Liabilities at fair value on a recurring basis
Liabilities, Fair Value Disclosure on Recurring Basis		0	0
Fair Value, Inputs, Level 2 [Member] | Power Contracts Assets [Member]
Assets at fair value on a recurring basis
Derivative Asset		0	0
Fair Value, Inputs, Level 2 [Member] | Gas Hedge Contracts Assets [Member]
Assets at fair value on a recurring basis
Derivative Asset		0
Fair Value, Inputs, Level 2 [Member] | Fixed Transmission Rights (FTRs) [Member]
Assets at fair value on a recurring basis
Derivative Asset		0	0
Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash Equivalents, at Carrying Value		0	0
Assets at fair value on a recurring basis
Restricted Cash and Cash Equivalents, Current		0	0
Replacement Reserve Escrow		0	0
Equity Securities, FV-NI		0	0
Debt Securities		0	0
Liabilities at fair value on a recurring basis
Assets, Fair Value Disclosure		8,000,000	18,000,000
Financial and Nonfinancial Liabilities, Fair Value Disclosure		49,000,000	34,000,000
Fair Value, Inputs, Level 3 [Member] | Gas Hedge Contracts [Member]
Liabilities at fair value on a recurring basis
Liabilities, Fair Value Disclosure on Recurring Basis		0	0
Fair Value, Inputs, Level 3 [Member] | Power Contracts Liabilities [Member]
Liabilities at fair value on a recurring basis
Liabilities, Fair Value Disclosure on Recurring Basis		49,000,000	34,000,000
Fair Value, Inputs, Level 3 [Member] | Power Contracts Assets [Member]
Assets at fair value on a recurring basis
Derivative Asset		3,000,000	3,000,000
Fair Value, Inputs, Level 3 [Member] | Gas Hedge Contracts Assets [Member]
Assets at fair value on a recurring basis
Derivative Asset		0
Fair Value, Inputs, Level 3 [Member] | Fixed Transmission Rights (FTRs) [Member]
Assets at fair value on a recurring basis
Derivative Asset		5,000,000	15,000,000
Entergy New Orleans [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash Equivalents, at Carrying Value		0	19,651,000
Assets at fair value on a recurring basis
Restricted Cash and Cash Equivalents, Current		5,075,000	2,224,000
Replacement Reserve Escrow		81,300,000	80,900,000
Liabilities at fair value on a recurring basis
Assets, Fair Value Disclosure		86,900,000	104,100,000
Entergy New Orleans [Member] | Gas Hedge Contracts [Member]
Liabilities at fair value on a recurring basis
Liabilities, Fair Value Disclosure on Recurring Basis			100,000
Entergy New Orleans [Member] | Fixed Transmission Rights (FTRs) [Member]
Assets at fair value on a recurring basis
Derivative Asset		500,000	1,300,000
Entergy New Orleans [Member] | Fair Value Inputs Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash Equivalents, at Carrying Value			19,700,000
Assets at fair value on a recurring basis
Restricted Cash and Cash Equivalents, Current		5,100,000	2,200,000
Replacement Reserve Escrow		81,300,000	80,900,000
Liabilities at fair value on a recurring basis
Assets, Fair Value Disclosure		86,400,000	102,800,000
Entergy New Orleans [Member] | Fair Value Inputs Level 1 [Member] | Gas Hedge Contracts [Member]
Liabilities at fair value on a recurring basis
Liabilities, Fair Value Disclosure on Recurring Basis			100,000
Entergy New Orleans [Member] | Fair Value Inputs Level 1 [Member] | Fixed Transmission Rights (FTRs) [Member]
Assets at fair value on a recurring basis
Derivative Asset		0	0
Entergy New Orleans [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash Equivalents, at Carrying Value			0
Assets at fair value on a recurring basis
Restricted Cash and Cash Equivalents, Current		0	0
Replacement Reserve Escrow		0	0
Liabilities at fair value on a recurring basis
Assets, Fair Value Disclosure		0	0
Entergy New Orleans [Member] | Fair Value, Inputs, Level 2 [Member] | Gas Hedge Contracts [Member]
Liabilities at fair value on a recurring basis
Liabilities, Fair Value Disclosure on Recurring Basis			0
Entergy New Orleans [Member] | Fair Value, Inputs, Level 2 [Member] | Fixed Transmission Rights (FTRs) [Member]
Assets at fair value on a recurring basis
Derivative Asset		0	0
Entergy New Orleans [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash Equivalents, at Carrying Value			0
Assets at fair value on a recurring basis
Restricted Cash and Cash Equivalents, Current		0	0
Replacement Reserve Escrow		0	0
Liabilities at fair value on a recurring basis
Assets, Fair Value Disclosure		500,000	1,300,000
Entergy New Orleans [Member] | Fair Value, Inputs, Level 3 [Member] | Gas Hedge Contracts [Member]
Liabilities at fair value on a recurring basis
Liabilities, Fair Value Disclosure on Recurring Basis			0
Entergy New Orleans [Member] | Fair Value, Inputs, Level 3 [Member] | Fixed Transmission Rights (FTRs) [Member]
Assets at fair value on a recurring basis
Derivative Asset		500,000	1,300,000
Entergy Mississippi [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash Equivalents, at Carrying Value		7,000	36,943,000
Assets at fair value on a recurring basis
Replacement Reserve Escrow		32,600,000	32,400,000
Liabilities at fair value on a recurring basis
Assets, Fair Value Disclosure		33,300,000	71,500,000
Entergy Mississippi [Member] | Gas Hedge Contracts [Member]
Liabilities at fair value on a recurring basis
Liabilities, Fair Value Disclosure on Recurring Basis		800,000
Entergy Mississippi [Member] | Fixed Transmission Rights (FTRs) [Member]
Assets at fair value on a recurring basis
Derivative Asset		700,000	2,200,000
Entergy Mississippi [Member] | Fair Value Inputs Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash Equivalents, at Carrying Value			36,900,000
Assets at fair value on a recurring basis
Replacement Reserve Escrow		32,600,000	32,400,000
Liabilities at fair value on a recurring basis
Assets, Fair Value Disclosure		32,600,000	69,300,000
Entergy Mississippi [Member] | Fair Value Inputs Level 1 [Member] | Gas Hedge Contracts [Member]
Liabilities at fair value on a recurring basis
Liabilities, Fair Value Disclosure on Recurring Basis		800,000
Entergy Mississippi [Member] | Fair Value Inputs Level 1 [Member] | Fixed Transmission Rights (FTRs) [Member]
Assets at fair value on a recurring basis
Derivative Asset		0	0
Entergy Mississippi [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash Equivalents, at Carrying Value			0
Assets at fair value on a recurring basis
Replacement Reserve Escrow		0	0
Liabilities at fair value on a recurring basis
Assets, Fair Value Disclosure		0	0
Entergy Mississippi [Member] | Fair Value, Inputs, Level 2 [Member] | Gas Hedge Contracts [Member]
Liabilities at fair value on a recurring basis
Liabilities, Fair Value Disclosure on Recurring Basis		0
Entergy Mississippi [Member] | Fair Value, Inputs, Level 2 [Member] | Fixed Transmission Rights (FTRs) [Member]
Assets at fair value on a recurring basis
Derivative Asset		0	0
Entergy Mississippi [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash Equivalents, at Carrying Value			0
Assets at fair value on a recurring basis
Replacement Reserve Escrow		0	0
Liabilities at fair value on a recurring basis
Assets, Fair Value Disclosure		700,000	2,200,000
Entergy Mississippi [Member] | Fair Value, Inputs, Level 3 [Member] | Gas Hedge Contracts [Member]
Liabilities at fair value on a recurring basis
Liabilities, Fair Value Disclosure on Recurring Basis		0
Entergy Mississippi [Member] | Fair Value, Inputs, Level 3 [Member] | Fixed Transmission Rights (FTRs) [Member]
Assets at fair value on a recurring basis
Derivative Asset		700,000	2,200,000
Entergy Louisiana [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash Equivalents, at Carrying Value		237,019,000	43,112,000
Assets at fair value on a recurring basis
Restricted Cash and Cash Equivalents, Current		9,000,000	3,600,000
Replacement Reserve Escrow		291,200,000	289,500,000
Equity Securities, FV-NI	[1]	10,400,000	13,300,000
Debt Securities	[1]	555,700,000	532,900,000
Liabilities at fair value on a recurring basis
Assets, Fair Value Disclosure		1,949,500,000	1,631,400,000
Entergy Louisiana [Member] | Gas Hedge Contracts [Member]
Liabilities at fair value on a recurring basis
Liabilities, Fair Value Disclosure on Recurring Basis		300,000	1,100,000
Entergy Louisiana [Member] | Common trust funds valued using Net Asset Value [Domain]
Assets at fair value on a recurring basis
Available-for-sale Securities	[2]	841,900,000	738,800,000
Entergy Louisiana [Member] | Gas Hedge Contracts Assets [Member]
Assets at fair value on a recurring basis
Derivative Asset		1,500,000	1,900,000
Entergy Louisiana [Member] | Fixed Transmission Rights (FTRs) [Member]
Assets at fair value on a recurring basis
Derivative Asset		2,800,000	8,300,000
Entergy Louisiana [Member] | Fair Value Inputs Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash Equivalents, at Carrying Value		237,000,000	43,100,000
Assets at fair value on a recurring basis
Restricted Cash and Cash Equivalents, Current		9,000,000	3,600,000
Replacement Reserve Escrow		291,200,000	289,500,000
Equity Securities, FV-NI	[1]	10,400,000	13,300,000
Debt Securities	[1]	184,600,000	162,000,000
Liabilities at fair value on a recurring basis
Assets, Fair Value Disclosure		733,700,000	511,500,000
Entergy Louisiana [Member] | Fair Value Inputs Level 1 [Member] | Gas Hedge Contracts [Member]
Liabilities at fair value on a recurring basis
Liabilities, Fair Value Disclosure on Recurring Basis		300,000	700,000
Entergy Louisiana [Member] | Fair Value Inputs Level 1 [Member] | Gas Hedge Contracts Assets [Member]
Assets at fair value on a recurring basis
Derivative Asset		1,500,000	0
Entergy Louisiana [Member] | Fair Value Inputs Level 1 [Member] | Fixed Transmission Rights (FTRs) [Member]
Assets at fair value on a recurring basis
Derivative Asset		0	0
Entergy Louisiana [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash Equivalents, at Carrying Value		0	0
Assets at fair value on a recurring basis
Restricted Cash and Cash Equivalents, Current		0	0
Replacement Reserve Escrow		0	0
Equity Securities, FV-NI	[1]	0	0
Debt Securities	[1]	371,100,000	370,900,000
Liabilities at fair value on a recurring basis
Assets, Fair Value Disclosure		371,100,000	372,800,000
Entergy Louisiana [Member] | Fair Value, Inputs, Level 2 [Member] | Gas Hedge Contracts [Member]
Liabilities at fair value on a recurring basis
Liabilities, Fair Value Disclosure on Recurring Basis		0	400,000
Entergy Louisiana [Member] | Fair Value, Inputs, Level 2 [Member] | Gas Hedge Contracts Assets [Member]
Assets at fair value on a recurring basis
Derivative Asset		0	1,900,000
Entergy Louisiana [Member] | Fair Value, Inputs, Level 2 [Member] | Fixed Transmission Rights (FTRs) [Member]
Assets at fair value on a recurring basis
Derivative Asset		0	0
Entergy Louisiana [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash Equivalents, at Carrying Value		0	0
Assets at fair value on a recurring basis
Restricted Cash and Cash Equivalents, Current		0	0
Replacement Reserve Escrow		0	0
Equity Securities, FV-NI	[1]	0	0
Debt Securities	[1]	0	0
Liabilities at fair value on a recurring basis
Assets, Fair Value Disclosure		2,800,000	8,300,000
Entergy Louisiana [Member] | Fair Value, Inputs, Level 3 [Member] | Gas Hedge Contracts [Member]
Liabilities at fair value on a recurring basis
Liabilities, Fair Value Disclosure on Recurring Basis		0	0
Entergy Louisiana [Member] | Fair Value, Inputs, Level 3 [Member] | Gas Hedge Contracts Assets [Member]
Assets at fair value on a recurring basis
Derivative Asset		0	0
Entergy Louisiana [Member] | Fair Value, Inputs, Level 3 [Member] | Fixed Transmission Rights (FTRs) [Member]
Assets at fair value on a recurring basis
Derivative Asset		2,800,000	8,300,000
Entergy Arkansas [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash Equivalents, at Carrying Value		189,495,000	1,000
Assets at fair value on a recurring basis
Restricted Cash and Cash Equivalents, Current		8,218,000	4,666,000
Equity Securities, FV-NI	[1]	5,500,000	4,000,000
Debt Securities	[1]	391,000,000	381,300,000
Liabilities at fair value on a recurring basis
Assets, Fair Value Disclosure		1,196,100,000	920,100,000
Entergy Arkansas [Member] | Common trust funds valued using Net Asset Value [Domain]
Assets at fair value on a recurring basis
Available-for-sale Securities	[2]	600,800,000	526,700,000
Entergy Arkansas [Member] | Fixed Transmission Rights (FTRs) [Member]
Assets at fair value on a recurring basis
Derivative Asset		1,100,000	3,400,000
Entergy Arkansas [Member] | Fair Value Inputs Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash Equivalents, at Carrying Value		189,500,000
Assets at fair value on a recurring basis
Restricted Cash and Cash Equivalents, Current		8,200,000	4,700,000
Equity Securities, FV-NI	[1]	5,500,000	4,000,000
Debt Securities	[1]	99,200,000	94,800,000
Liabilities at fair value on a recurring basis
Assets, Fair Value Disclosure		302,400,000	103,500,000
Entergy Arkansas [Member] | Fair Value Inputs Level 1 [Member] | Fixed Transmission Rights (FTRs) [Member]
Assets at fair value on a recurring basis
Derivative Asset		0	0
Entergy Arkansas [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash Equivalents, at Carrying Value		0
Assets at fair value on a recurring basis
Restricted Cash and Cash Equivalents, Current		0	0
Equity Securities, FV-NI	[1]	0	0
Debt Securities	[1]	291,800,000	286,500,000
Liabilities at fair value on a recurring basis
Assets, Fair Value Disclosure		291,800,000	286,500,000
Entergy Arkansas [Member] | Fair Value, Inputs, Level 2 [Member] | Fixed Transmission Rights (FTRs) [Member]
Assets at fair value on a recurring basis
Derivative Asset		0	0
Entergy Arkansas [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash Equivalents, at Carrying Value		0
Assets at fair value on a recurring basis
Restricted Cash and Cash Equivalents, Current		0	0
Equity Securities, FV-NI	[1]	0	0
Debt Securities	[1]	0	0
Liabilities at fair value on a recurring basis
Assets, Fair Value Disclosure		1,100,000	3,400,000
Entergy Arkansas [Member] | Fair Value, Inputs, Level 3 [Member] | Fixed Transmission Rights (FTRs) [Member]
Assets at fair value on a recurring basis
Derivative Asset		1,100,000	3,400,000
Entergy Texas [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash Equivalents, at Carrying Value		22,203,000	30,000
Assets at fair value on a recurring basis
Restricted Cash and Cash Equivalents, Current		29,461,000	40,185,000
Liabilities at fair value on a recurring basis
Assets, Fair Value Disclosure		51,700,000
Entergy Texas [Member] | Fixed Transmission Rights (FTRs) [Member]
Liabilities at fair value on a recurring basis
Liabilities, Fair Value Disclosure on Recurring Basis		300,000	500,000
Entergy Texas [Member] | Fair Value Inputs Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash Equivalents, at Carrying Value		22,200,000
Assets at fair value on a recurring basis
Restricted Cash and Cash Equivalents, Current		29,500,000	40,200,000
Liabilities at fair value on a recurring basis
Assets, Fair Value Disclosure		51,700,000
Entergy Texas [Member] | Fair Value Inputs Level 1 [Member] | Fixed Transmission Rights (FTRs) [Member]
Liabilities at fair value on a recurring basis
Liabilities, Fair Value Disclosure on Recurring Basis		0	0
Entergy Texas [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash Equivalents, at Carrying Value		0
Assets at fair value on a recurring basis
Restricted Cash and Cash Equivalents, Current		0	0
Liabilities at fair value on a recurring basis
Assets, Fair Value Disclosure		0
Entergy Texas [Member] | Fair Value, Inputs, Level 2 [Member] | Fixed Transmission Rights (FTRs) [Member]
Liabilities at fair value on a recurring basis
Liabilities, Fair Value Disclosure on Recurring Basis		0.0	0
Entergy Texas [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash Equivalents, at Carrying Value		0
Assets at fair value on a recurring basis
Restricted Cash and Cash Equivalents, Current		0	0
Liabilities at fair value on a recurring basis
Assets, Fair Value Disclosure		0
Entergy Texas [Member] | Fair Value, Inputs, Level 3 [Member] | Fixed Transmission Rights (FTRs) [Member]
Liabilities at fair value on a recurring basis
Liabilities, Fair Value Disclosure on Recurring Basis		300,000	500,000
System Energy [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash Equivalents, at Carrying Value		158,244,000	95,617,000
Assets at fair value on a recurring basis
Equity Securities, FV-NI	[1]	4,700,000	4,400,000
Debt Securities	[1]	375,200,000	364,200,000
Liabilities at fair value on a recurring basis
Assets, Fair Value Disclosure		1,109,500,000	965,100,000
System Energy [Member] | Common trust funds valued using Net Asset Value [Domain]
Assets at fair value on a recurring basis
Available-for-sale Securities	[2]	571,400,000	500,900,000
System Energy [Member] | Fair Value Inputs Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash Equivalents, at Carrying Value		158,200,000	95,600,000
Assets at fair value on a recurring basis
Equity Securities, FV-NI	[1]	4,700,000	4,400,000
Debt Securities	[1]	226,800,000	224,500,000
Liabilities at fair value on a recurring basis
Assets, Fair Value Disclosure		389,700,000	324,500,000
System Energy [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash Equivalents, at Carrying Value		0	0
Assets at fair value on a recurring basis
Equity Securities, FV-NI	[1]	0	0
Debt Securities	[1]	148,400,000	139,700,000
Liabilities at fair value on a recurring basis
Assets, Fair Value Disclosure		148,400,000	139,700,000
System Energy [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash Equivalents, at Carrying Value		0	0
Assets at fair value on a recurring basis
Equity Securities, FV-NI	[1]	0	0
Debt Securities	[1]	0	0
Liabilities at fair value on a recurring basis
Assets, Fair Value Disclosure		$ 0	0
Fair Value, Measurements, Recurring [Member] | Gas Hedge Contracts Assets [Member]
Assets at fair value on a recurring basis
Derivative Asset			2,000,000
Fair Value, Measurements, Recurring [Member] | Fair Value Inputs Level 1 [Member] | Gas Hedge Contracts Assets [Member]
Assets at fair value on a recurring basis
Derivative Asset			0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Gas Hedge Contracts Assets [Member]
Assets at fair value on a recurring basis
Derivative Asset			2,000,000
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Gas Hedge Contracts Assets [Member]
Assets at fair value on a recurring basis
Derivative Asset			$ 0

[1] (a)The decommissioning trust funds hold equity and fixed income securities. Equity securities are invested to approximate the returns of major market indices. Fixed income securities are held in various governmental and corporate securities. See Note 9 to the financial statements herein for additional information on the investment portfolios.

[2] (b)Common trust funds are not publicly quoted, and are valued by the fund administrators using net asset value as a practical expedient. Accordingly, these funds are not assigned a level in the fair value table. The fund administrator of these investments allows daily trading at the net asset value and trades settle at a later date.