Rate Matters - East Companies (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2015 USD ($) $ / MWD $ / MWh	Dec. 31, 2014 USD ($)
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent	$ 4,950,000	$ 4,264,000
Appalachian Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent	1,061,715	857,872
Indiana Michigan Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent	818,168	536,152
Ohio Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent	1,150,864	$ 1,318,939
Kentucky 2014 Base Rate Case [Member]
Public Utilities, General Disclosures [Line Items]
Requested Net Increase in Rates	70,000
Recommended Net Increase in Rates as Proposed in Stipulation Agreement	45,000
Recommended Increase in Rider Rates as Proposed in Stipulation Agreement	68,000
Recommended Decrease in Annual Base Rates as Proposed in Stipulation Agreement	23,000
Amount of Storm Costs Recommended for Recovery as Proposed in Stipulation Agreement	12,000
Amount of Off-System Sales Margins Included in the Annual Base Rates as Proposed in Stipulation Agreement	$ 15,000
Percentage of Off-System Sales Margins Above the Amount in Base Rates to be Shared with Customers as Proposed in Stipulation Agreement	75.00%
Percentage of Off-System Sales Margins Above the Amount in Base Rates to be Retained by KPCo as Proposed in Stipulation Agreement	25.00%
Approved Net Revenue Increase	$ 45,000
Amount of IGCC and Carbon Capture Costs Approved for Recovery	$ 2,000
Recovery Period of Approved IGCC and Carbon Capture Costs	25 years
Kentucky Fuel Adjustment Clause Review [Member]
Public Utilities, General Disclosures [Line Items]
Amount of Regulatory Disallowance Resulting from a Commission Order	$ 36,000
Kingsport 2015 Base Rate Case [Member]
Public Utilities, General Disclosures [Line Items]
Requested Base Rate Increase	$ 12,000
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) | $ / MWh	3.50
Retail Stability Rider for the Period June 2014 through May 2015 ($ per MWh) | $ / MWh	4.00
Amount of Retail Stability Rider Applied to the Deferred Capacity Costs ($ per MWh) | $ / MWh	1.00
Retail Stability Rider Rate to be Continued Until Capacity Deferral Balance is Collected as Ordered by the PUCO ($ per MWh) | $ / MWh	4.00
Deferred Capacity Costs Recovery Period as Ordered by PUCO (in months)	32 months
Annual Retail Share of Fixed Fuel Costs	$ 90,000
Approved Return On Equity	10.20%
Future Commitment to Support the Development of a Large Solar Farm	$ 20,000
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) | $ / MWh	3.50
Retail Stability Rider for the Period June 2014 through May 2015 ($ per MWh) | $ / MWh	4.00
Amount of Retail Stability Rider Applied to the Deferred Capacity Costs ($ per MWh) | $ / MWh	1.00
Retail Stability Rider Rate to be Continued Until Capacity Deferral Balance is Collected as Ordered by the PUCO ($ per MWh) | $ / MWh	4.00
Deferred Capacity Costs Recovery Period as Ordered by PUCO (in months)	32 months
Annual Retail Share of Fixed Fuel Costs	$ 90,000
Approved Return On Equity	10.20%
Future Commitment to Support the Development of a Large Solar Farm	$ 20,000
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	65,000
Net Favorable Fuel Adjustment Recorded in 2012 Based on Fuel Adjustment Clause Audit Rehearing	30,000
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	65,000
Net Favorable Fuel Adjustment Recorded in 2012 Based on Fuel Adjustment Clause Audit Rehearing	30,000
Special Rate Mechanism For Ormet [Member]
Public Utilities, General Disclosures [Line Items]
Amount of Foregone Revenues to be Collected Through the Economic Development Rider as Approved in the Economic Development Rider Filing	39,000
Remaining Ormet Deferral Allowed to be Requested Upon PUCO Adoption of Ormet Stipulation Agreement	10,000
Amount of Remaining Foregone Revenues Objected to by an Intervenor	5,000
Deferred Fuel Adjustment Clause Related to Ormet Interim Arrangement as of September 2009	64,000
Unrecognized Equity Carrying Costs Related to Ormet Interim Arrangement as of September 2009	2,000
Special Rate Mechanism For Ormet [Member] | Ohio Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Amount of Foregone Revenues to be Collected Through the Economic Development Rider as Approved in the Economic Development Rider Filing	39,000
Remaining Ormet Deferral Allowed to be Requested Upon PUCO Adoption of Ormet Stipulation Agreement	10,000
Amount of Remaining Foregone Revenues Objected to by an Intervenor	5,000
Deferred Fuel Adjustment Clause Related to Ormet Interim Arrangement as of September 2009	64,000
Unrecognized Equity Carrying Costs Related to Ormet Interim Arrangement as of September 2009	2,000
Transmission Distribution and Storage System Improvement Charge (TDSIC) [Member]
Public Utilities, General Disclosures [Line Items]
Estimated Cost Of Capital Improvements And Associated Operation And Maintenance Expenses	787,000
Reduction to the Estimated Cost of Capital Improvements and Associated Operation and Maintenance Expenses	117,000
Transmission Distribution and Storage System Improvement Charge (TDSIC) [Member] | Indiana Michigan Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Estimated Cost Of Capital Improvements And Associated Operation And Maintenance Expenses	787,000
Reduction to the Estimated Cost of Capital Improvements and Associated Operation and Maintenance Expenses	117,000
Virginia Regulatory Asset Proceeding - 2015 [Member]
Public Utilities, General Disclosures [Line Items]
Amounts Of Regulatory Assets Under Review In Separate Proceeding	11,000
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	$ 11,000
West Virginia Base Rate Case [Member]
Public Utilities, General Disclosures [Line Items]
Approved Return On Equity	9.75%
Approved Base Rate Increase	$ 99,000
Amount of Annual Delayed Customer Billing to Residential Customers	25,000
Approved Annual Vegetation Management Rider	45,000
Approved Annual Amortization Of Certain Deferred Costs	$ 89,000
West Virginia Base Rate Case [Member] | Appalachian Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Approved Return On Equity	9.75%
Approved Base Rate Increase	$ 85,000
Amount of Annual Delayed Customer Billing to Residential Customers	22,000
Approved Annual Vegetation Management Rider	38,000
Approved Annual Amortization Of Certain Deferred Costs	77,000
Deferred Capacity Costs [Member] | Ohio Electric Security Plan Filing [Member]
Public Utilities, General Disclosures [Line Items]
Capacity Deferral Balance as of May 2015 Subject to Audit by the PUCO	444,000
Regulatory Assets, Noncurrent	392,000
Amount of Deferred Capacity Costs Collected from Customers	183,000
Deferred Capacity Costs [Member] | Ohio Electric Security Plan Filing [Member] | Ohio Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Capacity Deferral Balance as of May 2015 Subject to Audit by the PUCO	444,000
Regulatory Assets, Noncurrent	392,000
Amount of Deferred Capacity Costs Collected from Customers	183,000
Big Sandy Plant, Unit 2 [Member]
Public Utilities, General Disclosures [Line Items]
Amount Reclassified as Regulatory Assets Upon Retirement of the Plant	$ 194,000
Amortization Period of Approved Regulatory Assets Related to Plant Retirement	25 years
Tanners Creek Plant, Units 1 - 4 [Member]
Public Utilities, General Disclosures [Line Items]
Amount Reclassified as Regulatory Assets Upon Retirement of the Plant	$ 265,000
Amortization Period of Approved Regulatory Assets Related to Plant Retirement	29 years
Amount Reclassified as Regulatory Assets Upon Plant Retirement Currently Not Being Amortized	$ 38,000
Tanners Creek Plant, Units 1 - 4 [Member] | Indiana Michigan Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Amount Reclassified as Regulatory Assets Upon Retirement of the Plant	$ 265,000
Amortization Period of Approved Regulatory Assets Related to Plant Retirement	29 years
Amount Reclassified as Regulatory Assets Upon Plant Retirement Currently Not Being Amortized	$ 38,000