-Network: (11 - Statement - Statement Of Income Alternative)

-Income Statement [Abstract] {ID1}

-Statement [Table] {ID2}

-Statement [Line Items] {ID3}

Operating revenues {ID4}

-Operating expenses: {ID5}

Fuel {ID6}

Purchased power and transmission {ID7}

Deferred energy costs, net {ID8}

Operations and maintenance {ID9}

Depreciation and amortization {ID10}

Taxes other than income taxes {ID11}

Total operating expenses {ID12}

Operating income {ID13}

Other income (expense), net {ID14}

Interest expense {ID15}

Income before income taxes {ID16}

Income tax expense {ID17}

Net income {ID18}

Less net income attributable to noncontrolling interest {ID19}

Net income attributable to Allegheny Energy, Inc. {ID20}

-Earnings per share attributable to Allegheny Energy, Inc.: {ID21}

Basic {ID22}

Diluted {ID23}

-Average shares outstanding: {ID24}

Basic {ID25}

Diluted {ID26}

Dividends per share {ID27}

-Network: (12 - Statement - Statement Of Cash Flows Indirect)

-Statement of Cash Flows [Abstract] {ID28}

-Statement [Table] {ID29}

-Statement [Line Items] {ID30}

-Cash Flows From Operating Activities: {ID31}

Net income {ID32}

-Adjustments for non-cash items included in income: {ID33}

Depreciation and amortization {ID34}

Amortization of debt related costs {ID35}

Amortization of liability for adverse power purchase commitment {ID36}

Amortization of Pennsylvania stranded costs {ID37}

Provision for uncollectible accounts {ID38}

Deferred income taxes and investment tax credit, net {ID39}

Deferred energy costs, net {ID40}

Stock-based compensation expense {ID41}

Unrealized gains on derivative contracts, net {ID42}

Pension and other postretirement employee benefit plan expense {ID43}

Pension and other postretirement employee benefit plan contributions {ID44}

Deferred revenue - Fort Martin scrubber project {ID45}

Deferred revenue - Virginia {ID46}

Uncollected transmission revenue {ID47}

Other, net {ID48}

-Changes in certain assets and liabilities: {ID49}

Accounts receivable, net {ID50}

Materials, supplies and fuel {ID51}

Prepaid taxes {ID52}

Collateral deposits {ID53}

Accounts payable {ID54}

Accrued taxes {ID55}

Accrued interest {ID56}

Regulatory assets {ID57}

Deferred income taxes {ID58}

Regulatory liabilities {ID59}

Distributions from equity method investee {ID60}

Assets and liabilities held for sale {ID61}

Other operating assets and liabilities {ID62}

Net cash provided by operating activities {ID63}

-Cash Flows From Investing Activities: {ID64}

Capital expenditures {ID65}

Proceeds from asset sales {ID66}

Purchase of Merrill Lynch interest in subsidiary {ID67}

Decrease in restricted funds {ID68}

Other investments {ID69}

Net cash used in investing activities {ID70}

-Cash Flows From Financing Activities: {ID71}

Issuance of long-term debt {ID72}

Repayment of long-term debt {ID73}

Equity contribution to PATH, LLC by the joint venture partner {ID74}

Distribution on behalf of noncontrolling interest {ID75}

Payments on capital lease obligations {ID76}

Share-based excess tax benefits {ID77}

Proceeds from exercise of employee stock options {ID78}

Cash dividends paid on common stock {ID79}

Net cash provided by financing activities {ID80}

Net decrease in cash and cash equivalents {ID81}

Cash and cash equivalents at beginning of period {ID82}

Cash and cash equivalents at end of period {ID83}

-Supplemental Cash Flows Information: {ID84}

Cash paid during the period for interest (net of amounts capitalized) {ID85}

Accounts payable at June 30 relating to capital expenditures {ID86}

-Network: (13 - Statement - Statement Of Financial Position Classified)

-Statement of Financial Position [Abstract] {ID87}

-Statement [Table] {ID88}

-Statement [Line Items] {ID89}

-ASSETS {ID90}

-Current Assets: {ID91}

Cash and cash equivalents {ID92}

-Accounts receivable: {ID93}

Customer {ID94}

Unbilled utility revenue {ID95}

Wholesale and other {ID96}

Allowance for uncollectible accounts {ID97}

Materials and supplies {ID98}

Fuel {ID99}

Deferred income taxes {ID100}

Prepaid taxes {ID101}

Collateral deposits {ID102}

Derivative assets {ID103}

Regulatory assets {ID104}

Assets held for sale {ID105}

Other {ID106}

Total current assets {ID107}

-Property, Plant and Equipment: {ID108}

Generation {ID109}

Transmission {ID110}

Distribution {ID111}

Other {ID112}

Accumulated depreciation {ID113}

Subtotal {ID114}

Construction work in progress {ID115}

Property, plant and equipment held for sale, net {ID116}

Total property, plant and equipment, net {ID117}

-Investments and Other Assets: {ID118}

Goodwill {ID119}

Restricted funds-Fort Martin scrubber project {ID120}

Investments in unconsolidated affiliates {ID121}

Other {ID122}

Total investments and other assets {ID123}

-Deferred Charges: {ID124}

Regulatory assets {ID125}

Derivative assets {ID126}

Assets held for sale {ID127}

Other {ID128}

Total deferred charges {ID129}

Total Assets {ID130}

-LIABILITIES AND EQUITY {ID131}

-Current Liabilities: {ID132}

Long-term debt due within one year {ID133}

Accounts payable {ID134}

Accrued taxes {ID135}

Payable to PJM for FTRs {ID136}

Derivative liabilities {ID137}

Regulatory liabilities {ID138}

Accrued interest {ID139}

Security deposits {ID140}

Liabilities associated with assets held for sale {ID141}

Other {ID142}

Total current liabilities {ID143}

Long-term Debt, excluding amounts due within one year {ID144}

-Deferred Credits and Other Liabilities: {ID145}

Derivative liabilities {ID146}

Income taxes payable {ID147}

Investment tax credit {ID148}

Deferred income taxes {ID149}

Regulatory liabilities {ID150}

Pension and other postretirement employee benefit plan liabilities {ID151}

Adverse power purchase commitment {ID152}

Liabilities associated with assets held for sale {ID153}

Other {ID154}

Total deferred credits and other liabilities {ID155}

Commitments and Contingencies (Note 15) {ID156}

-Equity: {ID157}

Common stock-$1.25 par value per share, 260 million shares authorized and 169,532,084 and 169,413,887 shares issued at June 30, 2009 and December 31, 2008, respectively {ID158}

Other paid-in capital {ID159}

Retained earnings {ID160}

Treasury stock at cost-49,493 shares {ID161}

Accumulated other comprehensive loss {ID162}

Total Allegheny Energy, Inc. common stockholders' equity {ID163}

Noncontrolling interest {ID164}

Total equity {ID165}

Total Liabilities and Equity {ID166}

-Network: (14 - Statement - Statement Of Financial Position Classified (Parenthetical))

-Statement of Financial Position [Abstract] {ID167}

-Statement [Table] {ID168}

-Statement [Line Items] {ID169}

Common stock, par value {ID170}

Common stock, shares authorized {ID171}

Common stock, shares issued {ID172}

Treasury stock at cost, shares {ID173}

-Network: (15 - Statement - Statement Of Shareholders Equity And Other Comprehensive Income)

-Statement of Stockholders' Equity [Abstract] {ID174}

-Statement [Table] {ID175}

-Statement, Equity Components [Axis] {ID176}

-Equity Component [Domain] {ID177}

Shares outstanding {ID178}

Common stock {ID179}

Other paid-in capital {ID180}

Retained earnings {ID181}

Treasury stock {ID182}

Accumulated other comprehensive loss {ID183}

Energy, Inc. common stockholders' equity {ID184}

Energy, Inc. common Noncontrolling interest {ID185}

-Statement [Line Items] {ID186}

Beginning Balance {ID187}

Beginning Balance {ID188}

Net income {ID189}

Defined benefit pension and other benefit plan amortization, net of tax of $555 in 3 months ended June 30th ,2009, $1,126 in 6 months ended June 30th, 2009, $287 in 3 months ended June 30th, 2008 and $621 in 6 months ended June 30th, 2008 {ID190}

Cash flow hedges, net of tax of $8,462 in 3 months ended June 30th, 2009, $4,868 in 6 months ended June 30th, 2009, $19,785 in 3 months ended June 30th, 2008 and $44,171 6 months ended June 30th 2008 {ID191}

Unrealized losses on available-for-sale securities, net of tax of $1 in 3 months ended June 30th, 2008 and $1 in 6 months ended June 30th, 2008 {ID192}

Distribution on behalf of noncontrolling interest {ID193}

Purchase of minority interest in AE Supply {ID194}

Equity contribution to PATH, LLC by the joint venture partner {ID195}

Dividends on common stock {ID196}

-Stock-based compensation expense: {ID197}

Stock units {ID198}

Non-employee director stock awards {ID199}

Non-employee director stock awards {ID200}

Stock options {ID201}

Performance shares {ID202}

Restricted shares {ID203}

Restricted shares {ID204}

Exercise of stock options {ID205}

Exercise of stock options {ID206}

Settlement of stock units {ID207}

Settlement of stock units {ID208}

Dividends on stock units {ID209}

Share-based excess tax benefits {ID210}

Other {ID211}

Ending Balance {ID212}

Ending Balance {ID213}

-Network: (16 - Statement - Statement Of Shareholders Equity And Other Comprehensive Income (Parenthetical))

-Statement of Stockholders' Equity [Abstract] {ID214}

-Statement [Table] {ID215}

-Statement, Equity Components [Axis] {ID216}

-Equity Component [Domain] {ID217}

Shares outstanding {ID218}

Common stock {ID219}

Other paid-in capital {ID220}

Retained earnings {ID221}

Treasury stock {ID222}

Accumulated other comprehensive loss {ID223}

Energy, Inc. common stockholders' equity {ID224}

Energy, Inc. common Noncontrolling interest {ID225}

-Statement [Line Items] {ID226}

Defined benefit pension and other benefit plan amortization, tax {ID227}

Cash flow hedges, tax {ID228}

Unrealized losses on available-for-sale securities, tax {ID229}

-Network: (17 - Disclosure - Notes to Financial Statements)

-Notes to Financial Statements [Abstract] {ID230}

NOTE 1: BASIS OF PRESENTATION {ID231}

NOTE 2: RECENT ACCOUNTING PRONOUNCEMENTS {ID232}

NOTE 3: ASSETS HELD FOR SALE {ID233}

NOTE 4: REGULATORY ASSETS AND LIABILITIES {ID234}

NOTE 5: INCOME TAXES {ID235}

NOTE 6: COMMON STOCK AND DEBT {ID236}

NOTE 7: BUSINESS SEGMENTS {ID237}

NOTE 8: FAIR VALUE MEASUREMENTS, DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES {ID238}

NOTE 9: STOCK-BASED COMPENSATION {ID239}

NOTE 10: PENSION BENEFITS AND POSTRETIREMENT BENEFITS OTHER THAN PENSIONS {ID240}

NOTE 11: FAIR VALUE OF FINANCIAL INSTRUMENTS {ID241}

NOTE 12: COMPREHENSIVE INCOME AND ACCUMULATED OTHER COMPREHENSIVE LOSS {ID242}

NOTE 13: EARNINGS PER SHARE {ID243}

NOTE 14: OTHER INCOME (EXPENSE), NET {ID244}

NOTE 15: COMMITMENTS AND CONTINGENCIES {ID245}

NOTE 16: SUBSEQUENT EVENT {ID246}

-Network: (18 - Disclosure - Document Information)

-Document Information [Text Block] {ID247}

Document Type {ID248}

Amendment Flag {ID249}

Amendment Description {ID250}

Document Period End Date {ID251}

-Network: (19 - Disclosure - Entity Information)

-Entity [Text Block] {ID252}

Trading Symbol {ID253}

Entity Registrant Name {ID254}

Entity Central Index Key {ID255}

Current Fiscal Year End Date {ID256}

Entity Well-known Seasoned Issuer {ID257}

Entity Current Reporting Status {ID258}

Entity Voluntary Filers {ID259}

Entity Filer Category {ID260}

Entity Common Stock, Shares Outstanding {ID261}

Entity Public Float {ID262}

ALLEGHENY ENERGY, INC XBRL Taxonomy Presentation Networks