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- Definition

Maximum Percentage of transfer performance shares to common stock based on actual Shareholder Return.

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Minimum Percentage of transfer performance shares to common stock based on actual Shareholder Return.

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Number Of Additional Types Of Performance Share Units

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Percentage Of Total Performance Share Units Granted

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- Definition

Share based compensation arrangement by share based payment award fair value assumptions weighted average grant date fair value.

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- Definition

Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

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Unrecognized cost of unvested share-based compensation awards.

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- Definition

Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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- Definition

The total recognized tax benefit related to compensation cost for equity-based payment arrangements recognized in income during the period.

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Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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- Definition

The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

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- Definition

The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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- Definition

The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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- Definition

The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

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The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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- Definition

As of the balance sheet date, the number of shares into which fully vested and expected to vest stock options outstanding can be converted under the option plan.

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Common Stock and Stock Compensation - Textual Performance Shares (Details) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2016 USD ($) share_unit_type $ / shares shares	Dec. 31, 2015 USD ($) $ / shares shares	Dec. 31, 2014 USD ($) $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Minimum Percentage of transfer performance shares to common stock based on actual Total Shareholder Return	0.00%
Maximum Percentage of transfer performance shares to common stock based on actual Total Shareholder Return	200.00%
Total compensation cost for award recognized in income	$ 3	$ 6	$ 27
Total compensation cost for award recognized in income, tax benefit	$ 1	$ 2	10
EPS-based Portion Of The Performance Share Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of total performance share units granted	25.00%
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period of performance share units issued under Performance Share Plan	3 years
Performance share units, unvested (in shares) \| shares	3,224,539	2,480,392
Vested and expected to best (in shares) \| shares	0
Equity instrument, granted (in shares) \| shares	1,717,167
Equity instruments, vested (in shares) \| shares	937,121
Equity instruments, forfeited (in shares) \| shares	35,899
Total compensation cost for award recognized in income	$ 96	$ 88	33
Total compensation cost for award recognized in income, tax benefit	37	$ 34	$ 13
Total unrecognized compensation cost related to award	$ 32
Total unrecognized compensation cost related to award, weighted average period	22 months
EPS-based and ROE-based Performance Share Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of additional types of performance share units \| share_unit_type	2
Initial assumed percentage payout at end of performance period	100.00%
Equity instrument granted in period, weighted average grant date fair value (in dollars per share) \| $ / shares	$ 48.87	$ 47.75
ROE-based Portion Of The Performance Share Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of total performance share units granted	25.00%
TSR-based Portion Of The Performance Share Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of total performance share units granted	50.00%
Alabama Power [Member] \| EPS-based Portion Of The Performance Share Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of total performance share units granted	25.00%
Alabama Power [Member] \| Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period of performance share units issued under Performance Share Plan	3 years
Minimum Percentage of transfer performance shares to common stock based on actual Total Shareholder Return	0.00%
Maximum Percentage of transfer performance shares to common stock based on actual Total Shareholder Return	200.00%
Equity instrument granted in period, weighted average grant date fair value (in dollars per share) \| $ / shares	$ 45.15	$ 46.42	$ 37.54
Equity instrument, granted (in shares) \| shares	249,065	214,709	176,070
Total compensation cost for award recognized in income	$ 15	$ 13	$ 5
Total compensation cost for award recognized in income, tax benefit	6	$ 5	$ 2
Total unrecognized compensation cost related to award	$ 3
Total unrecognized compensation cost related to award, weighted average period	22 months
Alabama Power [Member] \| EPS-based and ROE-based Performance Share Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of additional types of performance share units \| share_unit_type	2
Initial assumed percentage payout at end of performance period	100.00%
Equity instrument granted in period, weighted average grant date fair value (in dollars per share) \| $ / shares	$ 48.86	$ 47.78
Alabama Power [Member] \| ROE-based Portion Of The Performance Share Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of total performance share units granted	25.00%
Alabama Power [Member] \| TSR-based Portion Of The Performance Share Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of total performance share units granted	50.00%
Georgia Power [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period of performance share units issued under Performance Share Plan	3 years
Minimum Percentage of transfer performance shares to common stock based on actual Total Shareholder Return	0.00%
Maximum Percentage of transfer performance shares to common stock based on actual Total Shareholder Return	200.00%
Georgia Power [Member] \| EPS-based Portion Of The Performance Share Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of total performance share units granted	25.00%
Georgia Power [Member] \| Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Equity instrument granted in period, weighted average grant date fair value (in dollars per share) \| $ / shares	$ 45.17	$ 46.41	$ 37.54
Equity instrument, granted (in shares) \| shares	261,434	236,804	176,224
Total compensation cost for award recognized in income	$ 15	$ 15	$ 6
Total compensation cost for award recognized in income, tax benefit	6	$ 6	$ 2
Total unrecognized compensation cost related to award	$ 4
Total unrecognized compensation cost related to award, weighted average period	22 months
Georgia Power [Member] \| EPS-based and ROE-based Performance Share Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of additional types of performance share units \| share_unit_type	2
Initial assumed percentage payout at end of performance period	100.00%
Equity instrument granted in period, weighted average grant date fair value (in dollars per share) \| $ / shares	$ 48.84	$ 47.78
Georgia Power [Member] \| ROE-based Portion Of The Performance Share Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of total performance share units granted	25.00%
Georgia Power [Member] \| TSR-based Portion Of The Performance Share Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of total performance share units granted	50.00%
Gulf Power [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period of performance share units issued under Performance Share Plan	3 years
Minimum Percentage of transfer performance shares to common stock based on actual Total Shareholder Return	0.00%
Maximum Percentage of transfer performance shares to common stock based on actual Total Shareholder Return	200.00%
Fair value assumptions weighted average grant date fair value (in dollars per share) \| $ / shares		$ 2.20
Gulf Power [Member] \| EPS-based Portion Of The Performance Share Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of total performance share units granted	25.00%
Gulf Power [Member] \| Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Equity instrument, granted (in shares) \| shares	57,333	48,962	37,829
Fair value assumptions weighted average grant date fair value (in dollars per share) \| $ / shares	$ 45.18	$ 46.38	$ 37.54
Total compensation cost for award recognized in income	$ 3	$ 2	$ 1
Total compensation cost for award recognized in income, tax benefit	1
Total unrecognized compensation cost related to award	$ 2
Total unrecognized compensation cost related to award, weighted average period	22 months
Gulf Power [Member] \| EPS-based and ROE-based Performance Share Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of additional types of performance share units \| share_unit_type	2
Initial assumed percentage payout at end of performance period	100.00%
Equity instrument granted in period, weighted average grant date fair value (in dollars per share) \| $ / shares	$ 48.83	$ 47.75
Gulf Power [Member] \| ROE-based Portion Of The Performance Share Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of total performance share units granted	25.00%
Gulf Power [Member] \| TSR-based Portion Of The Performance Share Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of total performance share units granted	50.00%
Mississippi Power [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period of performance share units issued under Performance Share Plan	3 years
Mississippi Power [Member] \| EPS-based Portion Of The Performance Share Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of total performance share units granted	25.00%
Mississippi Power [Member] \| Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Minimum Percentage of transfer performance shares to common stock based on actual Total Shareholder Return	0.00%
Maximum Percentage of transfer performance shares to common stock based on actual Total Shareholder Return	200.00%
Equity instrument granted in period, weighted average grant date fair value (in dollars per share) \| $ / shares	$ 45.17	$ 46.41	$ 37.54
Equity instrument, granted (in shares) \| shares	62,435	53,909	49,579
Total compensation cost for award recognized in income	$ 4	$ 4	$ 2
Total compensation cost for award recognized in income, tax benefit	1	$ 2	$ 1
Total unrecognized compensation cost related to award	$ 1
Total unrecognized compensation cost related to award, weighted average period	22 months
Mississippi Power [Member] \| EPS-based and ROE-based Performance Share Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of additional types of performance share units \| share_unit_type	2
Initial assumed percentage payout at end of performance period	100.00%
Equity instrument granted in period, weighted average grant date fair value (in dollars per share) \| $ / shares	$ 48.84	$ 47.77
Mississippi Power [Member] \| ROE-based Portion Of The Performance Share Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of total performance share units granted	25.00%
Mississippi Power [Member] \| TSR-based Portion Of The Performance Share Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of total performance share units granted	50.00%