Long Term Debt (Details) (USD $)	3 Months Ended
Mar. 31, 2015
Debt Instrument [Line Items]
Number of WEC shares per Integrys share	1.128wec_NumberofWECsharesperIntegrysshare
Cash per share of Integrys common stock	$ 18.58wec_CashpershareofIntegryscommonstock

Number of WEC shares per Integrys share under the Merger agreement signed June 22, 2014

No definition available.

Name:	wec_NumberofWECsharesperIntegrysshare
Namespace Prefix:	wec_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration