Investments at fair value EBP, Investment, Fair Value Investment Contract Institution [Axis] Investment Contract Institution [Axis] Investment Contract Institution Maximum Maximum [Member] Base Pay Base Pay [Member] Guaranteed amount an employee earns as compensation. Excludes overtime, bonuses, etc. Statistical Measurement [Domain] Statistical Measurement [Domain] Participant Contribution, Pretax, Maximum Annual Compensation to Total Compensation, Percentage EBP, Participant Contribution, Pretax, Maximum Annual Compensation to Total Compensation, Percentage Total deductions EBP, Change in Net Asset Available for Benefit, Decrease Transamerica Premier Life Transamerica Premier Life [Member] Transamerica Premier Life Maximum percentage of assets covered by wrap contracts Maximum percentage of assets covered by wrap contracts Maximum percentage of the Blended Rate Income Fund's assets expected to be covered by wrap contracts. Employer Contribution Vesting Service Period EBP, Employer Contribution Vesting Service Period EBP, Employer Contribution Vesting Service Period Local 2150 Seasonal Local 2150 [Member] Local 2150 Money market mutual fund Money Market Funds [Member] Plan Interest in Master Trust EBP, Nonconsolidated, Plan Interest in Master Trust [Member] Reconciliation of Financial Statement to Form 5500 EBP, Reconciliation of Financial Statement to Form 5500 [Table Text Block] Eligibility service years Eligibility service period (years) Eligibility service period (years) Transfers as a result of transferred employees EBP, Change in Net Asset Available for Benefit, Transfer to (from) Plan Unfunded Commitment EBP, Fair Value, Investment, NAV, Unfunded Commitment Amendment Flag Amendment Flag EBP, Schedule of Asset Held for Investment [Table] EBP, Schedule of Asset Held for Investment [Table] Massachusetts Mutual Massachusetts Mutual [Member] Massachusetts Mutual EBP, Description of Plan and Accounting Change [Abstract] Receivables EBP, Receivable [Abstract] Fair Value Measurements EBP, Investment, Fair Value and NAV [Table Text Block] Participant Contribution Automatic Annual Increase Deferral Rate Participant Contribution Automatic Annual Increase Deferral Rate Participant Contribution Automatic Annual Increase Deferral Rate Monthly period subject to 500 hour eligibility requirement Monthly period subject to 500 hour eligibility requirement Monthly period subject to 500 hour eligibility requirement Investments [Domain] Investments [Domain] Vesting type [Axis] Vesting type [Axis] Vesting type Plan Interest in Master Trust, at contract value EBP, Investment, Plan Interest in Master Trust, Contract Value Reconciliation of Change in Net Assets Available for Benefits [Abstract] EBP, Reconciliation to Form 5500, Change in Net Asset Available for Benefit, Increase (Decrease) from Deemed Distribution [Abstract] Total Contributions EBP, Change in Net Asset Available for Benefit, Increase from Contribution Cost of Investment Acquired Cost of Investment Acquired Cost of investment acquired by employee stock purchase, saving, or similar plan (employee benefit plan (EBP)). Other income EBP, Change in Net Asset Available for Benefit, Increase (Decrease) from Other Investment Income (Loss) EBP 003 EBP 003 [Member] EBP 003 Retirement Saving Plan Adjustment from contract value to fair value Less: Adjustment from contract value to fair value, beginning of period Add: Adjustment from contract value to fair value, end of period EBP, Reconciliation to Form 5500, Net Asset Available for Benefit, Contract Value to Current Value Adjustment Contributions EBP, Contribution [Policy Text Block] Number of participant redemption restrictions Number of participant redemption restrictions Number of participant redemption restrictions on investments measured using the net asset value per share practical expedient. EBP, Schedule of Asset Held for Investment [Abstract] Reconciliations of Net Assets Available for Benefits [Abstract] EBP, Form 5500 Caption, Net Assets [Abstract] EBP, Accounting Policy [Table] EBP, Accounting Policy [Table] Total additions, net EBP, Change in Net Asset Available for Benefit, Increase Vesting type [Domain] Vesting type [Domain] Vesting type Assets Held for Investment, Total EBP, Asset Held for Investment Document Information [Line Items] Document Information [Line Items] Blended Rate Income Fund, at contract value EBP, Blended Rate Income Fund [Member] EBP, Blended Rate Income Fund Investment in Master Trust EBP, Master Trust [Text Block] Level 2 Fair Value, Inputs, Level 2 [Member] Employee Group [Axis] Employee Group [Axis] Employee Group Net increase in net assets available for benefits per the Form 5500 EBP, Form 5500 Caption, Net Income (Loss) EBP, Fully Benefit-Responsive Investment Contract [Line Items] EBP, Fully Benefit-Responsive Investment Contract [Line Items] Net increase in net assets available for benefits before net transfers Net increase in net assets available for benefits before net transfers per the financial statements EBP, Change in Net Asset Available for Benefit, Increase (Decrease) Related Party and Party-in-Interest Transactions EBP, Related Party and Party-in-Interest Transactions [Text Block] Employer Retirement Contribution Employer Retirement Contribution [Member] Employer Retirement Contribution Total Investments EBP, Investment, Fair and Contract Value Number of changes in valuation methodologies Number of changes in valuation methodologies Number of changes in valuation methodologies used to fair value investments. Local 2150 Temporary Local 2150 Temporary [Member] Local 2150 Temporary EBP, Related Party and Party-in-Interest Transactions [Abstract] Total receivables EBP, Receivable Employer contributions receivable EBP, Employer Contribution, Receivable Net appreciation in the fair value of investments EBP, Change in Net Asset Available for Benefit, Increase (Decrease) from Unrealized Gain (Loss) on Investment Participant Contribution, Automatic, Deferral Rate EBP, Participant Contribution, Automatic, Deferral Rate Benefits paid to participants EBP, Change in Net Asset Available for Benefit, Decrease from Payment to Participant Plan interest in Master Trust, at fair value EBP, Investment, Plan Interest in Master Trust, Fair Value Note Receivable From Participant Maximum Borrowing Term EBP, Note Receivable From Participant Account Maximum Borrowing Term EBP, Note Receivable From Participant Account Maximum Borrowing Term EBP, Statement of Net Asset Available for Benefit [Abstract] EBP, Accounting Policy [Line Items] EBP, Accounting Policy [Line Items] WEC common stock fund EBP, Employer, Common Stock Fund [Member] EBP, Reconciliation of Financial Statement to Form 5500 [Table] EBP, Reconciliation of Financial Statement to Form 5500 [Table] Investments in synthetic guaranteed investment contracts EBP, Fully Benefit-Responsive Investment Contract [Table Text Block] Employee Hiring Date [Domain] Employee Hiring Date [Domain] Employee Hiring Date Partial distribution withdrawals per plan year Partial distribution withdrawals per plan year Partial distribution withdrawals per plan year EBP, Master Trust [Table] EBP, Master Trust [Table] Level 1, Level 2, and Level 3 Fair Value, Inputs, Level 1, Level 2, and Level 3 [Member] Document Type Document Type Participant Loan, Interest Rate EBP, Asset Held for Investment, Participant Loan, Interest Rate EBP, Reconciliation of Financial Statement to Form 5500 [Abstract] Investments EBP, Investment, Fair and Contract Value [Abstract] Common collective trust funds Common Collective Trust [Member] Contribution Type [Axis] Contribution Type [Axis] Contribution Type Deductions from net assets attributed to EBP, Change in Net Asset Available for Benefit, Decrease [Abstract] Forfeited Nonvested Account, Decrease from Employer Contribution EBP, Forfeited Nonvested Account, Decrease from Employer Contribution Note receivables from participants EBP, Note Receivable from Participant Entity Registrant Name Entity Registrant Name Summary of Investments in Master Trust EBP, Master Trust [Table Text Block] Subsequent Events EBP, Subsequent Event [Policy Text Block] Hired prior to December 19, 2009 Hired prior to December 19, 2009 [Member] Hired prior to December 19, 2009 EmployeeBenefitPlanChangeInNetAssetAvailableForBenefitAbstract [Abstract] Employee Benefit Plan Change In Net Asset Available For Benefits Notes Receivable from Participants EBP, Note Receivable from Participant [Policy Text Block] Total investment income Net investment income EBP, Change in Net Asset Available for Benefit, Increase (Decrease) from Income (Loss) on Investment EBP, Related Party and Party-in-Interest Transactions [Line Items] EBP, Related Party and Party-in-Interest Transactions [Line Items] Level 3 Fair Value, Inputs, Level 3 [Member] Yield based on actual earnings Yield based on actual earnings Yield based on actual earnings Net assets available for benefits Net assets available for benefits, beginning of year Net assets available for benefits, end of year Net assets available for benefits EBP, Net Asset Available for Benefit Contributions EBP, Change in Net Asset Available for Benefit, Increase from Contribution [Abstract] Local 2006 Local 2006 [Member] Local 2006 Net assets available for benefits per the Form 5500 EBP, Form 5500 Caption, Net Assets Investments Measured at Net Asset Value Per Share Fair Value Measured at Net Asset Value Per Share [Member] EBP, Statement of Net Asset Available for Benefit [Line Items] EBP, Statement of Net Asset Available for Benefit [Line Items] Investment Income Recognition EBP, Master Trust [Policy Text Block] LRSP Contribution LRSP Contribution [Member] LRSP Contribution Rollover EBP, Change in Net Asset Available for Benefit, Increase from Participant Contribution, Rollover Forfeited Nonvested Account, Decrease from Administrative Expense EBP, Forfeited Nonvested Account, Decrease from Administrative Expense Legal Entity [Axis] Legal Entity [Axis] EBP, Description of Plan [Table] Employer Contributions [Table] EBP, Description of Plan [Table] Mutual funds Mutual Fund [Member] Entities [Table] Entities [Table] EBP, Related Party and Party-in-Interest Transactions [Table] EBP, Related Party and Party-in-Interest Transactions [Table] Note Receivable From Participant Account Basis Spread on Prime Rate EBP, Note Receivable From Participant Account Basis Spread on Prime Rate Spread on the current prime rate used to determine the interest rate charged on participant loans. EBP, Fully Benefit-Responsive Investment Contract [Table] EBP, Fully Benefit-Responsive Investment Contract [Table] Note Receivable from Participant, Account, Maximum Borrowing, Amount EBP, Note Receivable from Participant, Account, Maximum Borrowing, Amount Note Receivable from Participant, Account, Minimum Borrowing, Amount EBP, Note Receivable from Participant, Account, Minimum Borrowing, Amount American General Life Ins. Co. American General Life Ins. Co. [Member] American General Life Ins. Co. EBP, Fully Benefit-Responsive Investment Contract [Abstract] EBP Vesting Percentage upon Plan Termination EBP Vesting Percentage upon Plan Termination EBP Employee Vesting Percentage upon Plan Termination State Street Bank & Trust Co. - Boston State Street Bank & Trust Co. - Boston [Member] State Street Bank & Trust Co. - Boston Level 1 Fair Value, Inputs, Level 1 [Member] Guaranteed investment contracts held by master trust EBP, Fully Benefit-Responsive Investment Contract [Text Block] Consecutive 12 month periods to obtain 500 hours of service Consecutive 12 month periods to obtain 500 hours of service Consecutive 12 month periods to obtain 500 hours of service Gross Pay Gross Pay [Member] Employee's total compensation, includes base pay plus any additional earning such as overtime, bonuses, etc. Metropolitan Life Ins. Co. Metropolitan Life Ins. Co. [Member] Metropolitan Life Ins. Co. Statistical Measurement [Axis] Statistical Measurement [Axis] Additions to net assets attributed to EBP, Change in Net Asset Available for Benefit, Increase [Abstract] EBP, Statement of Change in Net Asset Available for Benefit [Table] EBP, Statement of Change in Net Asset Available for Benefit [Table] Payment of Benefits EBP, Payment to Participant [Policy Text Block] EBP, Master Trust [Line Items] EBP, Master Trust [Line Items] Participants EBP, Change in Net Asset Available for Benefit, Increase from Participant Contribution Basis of Accounting EBP, Basis of Accounting [Policy Text Block] Investment Contract Institution [Domain] Investment Contract Institution [Domain] Investment Contract Institution [Domain] Total investments EBP, Investment, Plan Interest in Master Trust, Fair and Contract Value Number of Shares Held EBP, Investment, Number of Shares Period to obtain 1,000 hours of service Period to obtain 1,000 hours of service Period to obtain 1,000 hours of service Security Type [Domain] Security Type [Domain] Security Type Common Stock Common Stock [Member] EBP, Master Trust [Abstract] Use of Estimates EBP, Use of Estimate [Policy Text Block] Schedule of Asset Held for Investment EBP, Schedule of Asset Held for Investment [Text Block] Cover [Abstract] Eligibility service hours within three consecutive 12 month periods Eligibility service hours within three consecutive 12 month periods Eligibility service hours within three consecutive 12 month periods Employer EBP, Change in Net Asset Available for Benefit, Increase from Employer Contribution, Cash Employee Hiring Date [Axis] Employee Hiring Date [Axis] Employee Hiring Date Prudential Ins. Co. of America Prudential Ins. Co. of America [Member] Prudential Ins. Co. of America EBP, Synthetic Investment Contract EBP, Synthetic Investment Contract [Member] Minimum Minimum [Member] Investments Sold Investments Sold Amount of selling price for investments sold by employee stock purchase, saving, or similar plan (employee benefit plan (EBP)). Investment Type [Axis] Investment Type [Axis] Interest income from notes receivable from participants EBP, Change in Net Asset Available for Benefit, Increase from Interest Income on Note Receivable from Participant PGL Local 18007 PGL Local 18007 [Member] PGL Local 18007 Compensation [Axis] Compensation [Axis] Types of Compensation Interest and dividend income EBP, Change in Net Asset Available for Benefit, Increase from Interest and Dividend Income on Investment Description of Plan Employer Contributions EBP, Description of Plan [Line Items] Description of Plan EBP, Description of Plan [Text Block] WPSC Local 420 WPSC Local 420 [Member] WPSC Local 420 Employee Group [Domain] Employee Group [Domain] Employee Group EBP, Statement of Change in Net Asset Available for Benefit [Line Items] EBP, Statement of Change in Net Asset Available for Benefit [Line Items] EBP, Statement of Net Asset Available for Benefit [Table] EBP, Statement of Net Asset Available for Benefit [Table] Age/Service Point Contribution [Member] Age/Service Point Contribution [Member] Age/Service Point Contribution EBP, Schedule of Asset Held for Investment [Line Items] EBP, Schedule of Asset Held for Investment [Line Items] EBP, Nonconsolidated, Master Trust and Plan Interest in Master Trust [Domain] EBP, Nonconsolidated, Master Trust and Plan Interest in Master Trust [Domain] WEC common stock EBP, Employer, Common Stock [Member] Investment income EBP, Change in Net Asset Available for Benefit, Increase (Decrease) from Income (Loss) on Investment [Abstract] Administrative expenses EBP, Change in Net Asset Available for Benefit, Decrease from Administrative Expense Short-term investment fund Short-term investment fund [Member] Short-term investment fund Investments at contract value EBP, Investment, Contract Value Pacific Life Ins. Co. Pacific Life Ins. Co. [Member] Pacific Life Ins. Co. Net Assets Available for Benefits EBP, Change in Net Asset Available for Benefit, Increase (Decrease) [Abstract] Non-represented management employees Non-represented management employees [Member] Non-represented management employees Employer contribution, matching percentage of eligible compensation EBP, Employer Contribution, Participant Compensation Matched, Percentage Minimum crediting rate Minimum crediting rate Minimum crediting rate that is guaranteed by wrap contracts. Number of units held EBP, Investment, Number of Units, Held in WEC Stock Fund Number of units held in investment fund EBP, Tax Status [Table] EBP, Tax Status [Table] EBP, Accounting Policy, Accounting Standard Update, and Change in Accounting Principle [Abstract] Dividend Income on Investment EBP, Change in Net Asset Available for Benefit, Increase from Dividend Income on Investment Fair Value Hierarchy and NAV [Domain] Fair Value Hierarchy and NAV [Domain] Potential fund yield Potential fund yield Potential yield of the blended rate income fund if there are significant redemptions when the market value is below the contract value. EBP, Tax Status [Abstract] Nationwide Life Ins. Co. Nationwide Life Ins. Co. [Member] Nationwide Life Ins. Co. Employer Contributions EBP, Contribution [Table Text Block] Plan interest in Master Trust investment income EBP, Change in Net Asset Available for Benefit, Increase (Decrease) from Change in Plan Interest in Master Trust EBP, Reconciliation of Financial Statement to Form 5500 [Line Items] EBP, Reconciliation of Financial Statement to Form 5500 [Line Items] Administrative Expenses EBP, Expense [Policy Text Block] Reconciliation of Financial Statement to Form 5500 EBP, Reconciliation of Financial Statement to Form 5500 [Text Block] Participant Loans EBP, Asset Held for Investment, Participant Loan, after Deemed Distribution Investment Valuation and Fair Value Measurements of Assets EBP, Investment [Policy Text Block] Contribution type [Domain] Contribution type [Domain] Contribution type Security Type [Axis] Security Type [Axis] Security Type Plan Termination EBP, Plan Termination [Text Block] Entity Central Index Key Entity Central Index Key Note Receivable from Participant, Maximum Number of Notes Outstanding EBP, Note Receivable from Participant, Maximum Number of Notes Outstanding EBP, Note Receivable from Participant, Maximum Number of Notes Outstanding Compensation [Domain] Compensation [Domain] Types of compensation EBP, Tax Status [Line Items] EBP, Tax Status [Line Items] Audits in progress Audits in progress Number of audits in progress for any tax period. Master Trust EBP, Nonconsolidated, Master Trust [Member] Additional company savings plans with assets in the master trust Additional company savings plans with assets in the master trust Additional company savings plans with assets in the master trust Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Accounting Policies EBP, Summary of Accounting Policy [Text Block] Maximum account balance that will require an automatic distribution through a lump-sum Maximum account balance that will require an automatic distribution through a lump-sum Maximum account balance that will require an automatic distribution through a lump-sum Cost of services provided by the Company Cost of services provided by the Company Cost of administrative and accounting services provided by the Company. Yield based on interest rate credited to participants Yield based on interest rate credited to participants Yield based on interest rate credited to participants Federal Tax Status EBP, Tax Status [Text Block] Note Receivable from Participant, Account, Maximum Borrowing, to Total Account, Percentage EBP, Note Receivable from Participant, Account, Maximum Borrowing, to Total Account, Percentage Note Receivable From Participant Period of Time of Reduction of Outstanding Loans EBP, Note Receivable From Participant Period of Time of Reduction of Outstanding Loans Period of time for which outstanding loans will reduce the amount a participant can borrow. Eligiblity service hours within one year of hire date Eligiblity service hours within one year of hire date Eligiblity service hours within one year of hire date JP Morgan Chase & Co. JP Morgan Chase & Co. [Member] JP Morgan Chase & Co. EBP, Nonconsolidated, Master Trust and Plan Interest in Master Trust [Axis] EBP, Nonconsolidated, Master Trust and Plan Interest in Master Trust [Axis] Entity [Domain] Entity [Domain] Forfeited Nonvested Account EBP, Forfeited Nonvested Account Employer contribution, matching percentage EBP, Employer Contribution, Matching Percentage Hired on or after December 19, 2009 Hired on or after December 19, 2009 [Member] Hired on or after December 19, 2009