Property, Plant, and Equipment - Balances (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019
Property, plant, and equipment
Accumulated depreciation	$ 9,364.7	$ 8,878.7
Net property, plant, and equipment	25,707.4	23,620.1
Costs incurred for repairs and restorations	35.2
Insurance proceeds received to cover damage to the PSB building	20.0
Accounts receivable recorded for future insurance recoveries	2.7
PSB building repair and restoration costs in other operation and maintenance expense	12.5
Regulated operations
Property, plant, and equipment
Accumulated depreciation	8,465.0	8,073.7
Net	20,631.9	19,102.6
CWIP	683.9	820.4
Net property, plant, and equipment	21,315.8	19,923.0
Regulated operations \| Electric - generation
Property, plant, and equipment
Property, plant, and equipment	7,015.3	6,858.8
Regulated operations \| Electric - distribution
Property, plant, and equipment
Property, plant, and equipment	7,455.5	7,018.1
Regulated operations \| Natural gas - distribution, storage, and transmission
Property, plant, and equipment
Property, plant, and equipment	12,730.0	11,602.7
Regulated operations \| Other
Property, plant, and equipment
Property, plant, and equipment	1,896.1	1,696.7
Non-regulated operations
Property, plant, and equipment
Accumulated depreciation	899.7	805.0
Net	4,056.5	3,672.3
CWIP	335.1	24.8
Net property, plant, and equipment	4,391.6	3,697.1
Non-regulated operations \| Other
Property, plant, and equipment
Property, plant, and equipment	41.8	88.8
Non-regulated operations \| We Power generation
Property, plant, and equipment
Property, plant, and equipment	3,238.8	3,245.7
Non-regulated operations \| Renewable generation
Property, plant, and equipment
Property, plant, and equipment	1,213.3	716.5
Non-regulated operations \| Natural gas storage
Property, plant, and equipment
Property, plant, and equipment	250.0	245.9
Non-regulated operations \| Corporate services
Property, plant, and equipment
Property, plant, and equipment	212.3	180.4
Non-Utility Energy Infrastructure \| Non-regulated operations
Property, plant, and equipment
Property, plant, and equipment	$ 4,702.1	$ 4,208.1

Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=6391035&loc=d3e2868-110229

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.14)
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of structure or a modification to a structure under construction. Includes recently completed structures or modifications to structures that have not been placed into service.

+ References

+ Details

Name:	us-gaap_ConstructionInProgressGross
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- 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.

+ References

No definition available.

+ Details

Name:	us-gaap_PropertyPlantAndEquipmentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount after accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business to produce goods and services and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(14))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6391035&loc=d3e2868-110229

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(8))
-URI http://asc.fasb.org/extlink&oid=120400017&loc=d3e572229-122910

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(13))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_PropertyPlantAndEquipmentNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Total costs incurred for repairs and restorations. Includes costs that were capitalized and expensed.

+ References

No definition available.

+ Details

Name:	wec_CostsIncurredForRepairsAndRestorations
Namespace Prefix:	wec_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of insurance proceeds received to cover the damage to the PSB Building

+ References

No definition available.

+ Details

Name:	wec_InsuranceProceedsReceivedToCoverDamageToPSBBuilding
Namespace Prefix:	wec_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of PSB building repair and restoration costs in other operation and maintenance expense

+ References

No definition available.

+ Details

Name:	wec_PSBBuildingRepairAndRestorationCostsInOtherOperationAndMaintenanceExpense
Namespace Prefix:	wec_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Gross amount of long-lived physical assets used in the normal conduct of business and not intended for resale. Amount excludes construction work in progress. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

+ References

No definition available.

+ Details

Name:	wec_PropertyPlantAndEquipmentGrossExcludingConstructionWorkInProgress
Namespace Prefix:	wec_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Long-lived physical assets that are held by an entity, excluding construction work in progress, for use in the production or supply of goods and services, for rental to others, or for administrative purposes and that are expected to provide economic benefit for more than one year; net of accumulated depreciation.

+ References

No definition available.

+ Details

Name:	wec_PropertyPlantAndEquipmentNetExcludingConstructionWorkInProgress
Namespace Prefix:	wec_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of accounts receivable recorded for future insurance recoveries

+ References

No definition available.

+ Details

Name:	wec_ReceivableRecordedForFutureInsuranceRecoveries
Namespace Prefix:	wec_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	us-gaap_PublicUtilityRegulatedOrUnregulatedStatusAxis=us-gaap_RegulatedOperationMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_ElectricGenerationEquipmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_ElectricDistributionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=wec_NaturalGasStorageTransportationandDistributionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_PropertyPlantAndEquipmentOtherTypesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PublicUtilityRegulatedOrUnregulatedStatusAxis=us-gaap_UnregulatedOperationMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=wec_WePowerGeneratingFacilitiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=wec_RenewableGenerationMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=wec_NaturalGasStorageEquipmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=wec_CorporateServicesEquipmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=wec_NonUtilityEnergyInfrastructureMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: