Rate Matters - East Companies (Details) $ in Millions	1 Months Ended	3 Months Ended
	Apr. 28, 2016 USD ($) $ / MWD	Mar. 31, 2016 USD ($) $ / MWD MW	Dec. 31, 2015 USD ($)
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent		$ 5,109.5	$ 5,140.3
Appalachian Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent		1,125.7	1,154.2
Indiana Michigan Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent		813.8	804.3
Ohio Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent		1,056.5	$ 1,113.0
Kingsport Base Rate Case - 2015 [Member]
Public Utilities, General Disclosures [Line Items]
Requested Base Rate Increase		$ 12.0
Requested Return on Equity		10.66%
Ohio Electric Security Plan Filing [Member]
Public Utilities, General Disclosures [Line Items]
PUCO-ordered Fixed Price per MW Day for Customers Who Switch During ESP Period | $ / MWD		188.88
Reliability Pricing Model Rate per MW Day in Effect through May 2014 | $ / MWD		34
Reliability Pricing Model Rate per MW Day in Effect from June 2014 through May 2015 | $ / MWD		150
Retail Stability Rider through May 2014 ($ Per MWh) | $ / MWD		3.50
Retail Stability Rider for the Period June 2014 through May 2015 ($ per MWh) | $ / MWD		4.00
Amount of Retail Stability Rider Applied to the Deferred Capacity Costs ($ per MWh) | $ / MWD		1.00
Retail Stability Rider Rate to be Continued Until Capacity Deferral Balance is Collected as Ordered by the PUCO ($ per MWh) | $ / MWD		4.00
Annual Retail Share of Fixed Fuel Costs		$ 90.0
Approved Return on Equity		10.20%
Return On Equity Proposed In PPA Stipulation Agreement		10.38%
Amount of Potential Customer Credits to be Included in the PPA Rider Over the Final Four Years as Proposed in Stipulation Agreement		$ 100.0
Solar Energy Projects to be Developed and Implemented by 2021 as Proposed in Stipulation Agreement (in MWs) | MW		400
Wind Energy Projects to be Developed and Implemented by 2021 as Proposed in Stipulation Agreement (in MWs) | MW		500
Percentage of Output to be Received from Solar and Wind Projects as Proposed in Stipulation Agreement		100.00%
Maximum Ownership Percentage of Solar and Wind Projects as Proposed in Stipulation Agreement		50.00%
Temporary Customer-Specific Rate Impact Cap Through May 2018		5.00%
Future Commitment to Support the Development of a Large Solar Farm		$ 20.0
Ohio Electric Security Plan Filing [Member] | June 2020 through May 2021 [Member]
Public Utilities, General Disclosures [Line Items]
Amount of Potential Customer Credits to be Included in the PPA Rider Over the Final Four Years as Proposed in Stipulation Agreement		10.0
Ohio Electric Security Plan Filing [Member] | June 2021 through May 2022 [Member]
Public Utilities, General Disclosures [Line Items]
Amount of Potential Customer Credits to be Included in the PPA Rider Over the Final Four Years as Proposed in Stipulation Agreement		20.0
Ohio Electric Security Plan Filing [Member] | June 2022 through May 2023 [Member]
Public Utilities, General Disclosures [Line Items]
Amount of Potential Customer Credits to be Included in the PPA Rider Over the Final Four Years as Proposed in Stipulation Agreement		30.0
Ohio Electric Security Plan Filing [Member] | June 2023 through May 2024 [Member]
Public Utilities, General Disclosures [Line Items]
Amount of Potential Customer Credits to be Included in the PPA Rider Over the Final Four Years as Proposed in Stipulation Agreement		$ 40.0
Ohio Electric Security Plan Filing [Member] | Ohio Power Co [Member]
Public Utilities, General Disclosures [Line Items]
PUCO-ordered Fixed Price per MW Day for Customers Who Switch During ESP Period | $ / MWD		188.88
Reliability Pricing Model Rate per MW Day in Effect through May 2014 | $ / MWD		34
Reliability Pricing Model Rate per MW Day in Effect from June 2014 through May 2015 | $ / MWD		150
Retail Stability Rider through May 2014 ($ Per MWh) | $ / MWD		3.50
Retail Stability Rider for the Period June 2014 through May 2015 ($ per MWh) | $ / MWD		4.00
Amount of Retail Stability Rider Applied to the Deferred Capacity Costs ($ per MWh) | $ / MWD		1.00
Retail Stability Rider Rate to be Continued Until Capacity Deferral Balance is Collected as Ordered by the PUCO ($ per MWh) | $ / MWD		4.00
Annual Retail Share of Fixed Fuel Costs		$ 90.0
Approved Return on Equity		10.20%
Return On Equity Proposed In PPA Stipulation Agreement		10.38%
Amount of Potential Customer Credits to be Included in the PPA Rider Over the Final Four Years as Proposed in Stipulation Agreement		$ 100.0
Solar Energy Projects to be Developed and Implemented by 2021 as Proposed in Stipulation Agreement (in MWs) | MW		400
Wind Energy Projects to be Developed and Implemented by 2021 as Proposed in Stipulation Agreement (in MWs) | MW		500
Percentage of Output to be Received from Solar and Wind Projects as Proposed in Stipulation Agreement		100.00%
Maximum Ownership Percentage of Solar and Wind Projects as Proposed in Stipulation Agreement		50.00%
Temporary Customer-Specific Rate Impact Cap Through May 2018		5.00%
Future Commitment to Support the Development of a Large Solar Farm		$ 20.0
Ohio Electric Security Plan Filing [Member] | Ohio Power Co [Member] | June 2020 through May 2021 [Member]
Public Utilities, General Disclosures [Line Items]
Amount of Potential Customer Credits to be Included in the PPA Rider Over the Final Four Years as Proposed in Stipulation Agreement		10.0
Ohio Electric Security Plan Filing [Member] | Ohio Power Co [Member] | June 2021 through May 2022 [Member]
Public Utilities, General Disclosures [Line Items]
Amount of Potential Customer Credits to be Included in the PPA Rider Over the Final Four Years as Proposed in Stipulation Agreement		20.0
Ohio Electric Security Plan Filing [Member] | Ohio Power Co [Member] | June 2022 through May 2023 [Member]
Public Utilities, General Disclosures [Line Items]
Amount of Potential Customer Credits to be Included in the PPA Rider Over the Final Four Years as Proposed in Stipulation Agreement		30.0
Ohio Electric Security Plan Filing [Member] | Ohio Power Co [Member] | June 2023 through May 2024 [Member]
Public Utilities, General Disclosures [Line Items]
Amount of Potential Customer Credits to be Included in the PPA Rider Over the Final Four Years as Proposed in Stipulation Agreement		40.0
Ohio Fuel Adjustment Clause Audit - 2009 [Member]
Public Utilities, General Disclosures [Line Items]
2008 Coal Contract Settlement Proceeds to be Applied to Deferred Fuel Balance as Originally Ordered by the PUCO		65.0
Net Favorable Fuel Adjustment Recorded in 2012 Based on Fuel Adjustment Clause Audit Rehearing		30.0
Ohio Fuel Adjustment Clause Audit - 2009 [Member] | Ohio Power Co [Member]
Public Utilities, General Disclosures [Line Items]
2008 Coal Contract Settlement Proceeds to be Applied to Deferred Fuel Balance as Originally Ordered by the PUCO		65.0
Net Favorable Fuel Adjustment Recorded in 2012 Based on Fuel Adjustment Clause Audit Rehearing		30.0
Special Rate Mechanism For Ormet [Member]
Public Utilities, General Disclosures [Line Items]
Deferred Fuel Adjustment Clause Related to Ormet Interim Arrangement as of September 2009		64.0
Unrecognized Equity Carrying Costs Related to Ormet Interim Arrangement as of September 2009		2.0
Special Rate Mechanism For Ormet [Member] | Ohio Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Deferred Fuel Adjustment Clause Related to Ormet Interim Arrangement as of September 2009		64.0
Unrecognized Equity Carrying Costs Related to Ormet Interim Arrangement as of September 2009		2.0
Virginia Regulatory Asset Proceeding - 2015 [Member]
Public Utilities, General Disclosures [Line Items]
Amounts Of Regulatory Assets Under Review In Separate Proceeding		8.0
Virginia Regulatory Asset Proceeding - 2015 [Member] | Appalachian Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Amounts Of Regulatory Assets Under Review In Separate Proceeding		8.0
West Virginia Deferred Base Rate Increase [Member]
Public Utilities, General Disclosures [Line Items]
Amount Of Annual Delayed Customer Billing To Residential Customers		25.0
Amount Of Recovery Requested Related To Delayed Billing Including Carrying Charges		29.0
West Virginia Deferred Base Rate Increase [Member] | Appalachian Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Amount Of Annual Delayed Customer Billing To Residential Customers		22.0
Amount Of Recovery Requested Related To Delayed Billing Including Carrying Charges		26.0
West Virginia Expanded Net Energy Charge (ENEC) - 2016 [Member]
Public Utilities, General Disclosures [Line Items]
Requested Annual Increase		108.0
West Virginia Expanded Net Energy Charge (ENEC) - 2016 [Member] | Appalachian Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Requested Annual Increase		$ 86.0
Deferred Capacity Costs [Member] | Ohio Electric Security Plan Filing [Member]
Public Utilities, General Disclosures [Line Items]
Deferred Capacity Costs Recovery Period as Ordered by PUCO (in months)		32 months
Capacity Deferral Balance As Of May 2015 Subject To Audit By PUCO		$ 444.0
Regulatory Assets, Noncurrent		320.0
Amount of Deferred Capacity Costs Collected from Customers		$ 266.0
Deferred Capacity Costs [Member] | Ohio Electric Security Plan Filing [Member] | Ohio Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Deferred Capacity Costs Recovery Period as Ordered by PUCO (in months)		32 months
Capacity Deferral Balance As Of May 2015 Subject To Audit By PUCO		$ 444.0
Regulatory Assets, Noncurrent		320.0
Amount of Deferred Capacity Costs Collected from Customers		$ 266.0
Subsequent Event [Member] | Ohio Electric Security Plan Filing [Member]
Public Utilities, General Disclosures [Line Items]
Energy Credit Offset Applied Against the Capacity Deferral Threshold (per MW day) | $ / MWD	147.41
Overstatement of Energy Credit Used in the Determination of the Capacity Deferral Threshold (per MW day) | $ / MWD	100.00
Significantly Excessive Earnings Test Threshold Previously Established for Ohio Power	12.00%
Significantly Excessive Earnings Test Threshold Remanded Back to the PUCO	12.00%
Gridsmart Investment as Proposed in Stipulation Agreement	$ 20.0
Subsequent Event [Member] | Ohio Electric Security Plan Filing [Member] | Ohio Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Energy Credit Offset Applied Against the Capacity Deferral Threshold (per MW day) | $ / MWD	147.41
Overstatement of Energy Credit Used in the Determination of the Capacity Deferral Threshold (per MW day) | $ / MWD	100.00
Significantly Excessive Earnings Test Threshold Previously Established for Ohio Power	12.00%
Significantly Excessive Earnings Test Threshold Remanded Back to the PUCO	12.00%
Gridsmart Investment as Proposed in Stipulation Agreement	$ 20.0