Acquisition (Details) (USD $) In Billions, except Share data, unless otherwise specified	9 Months Ended
	Sep. 30, 2014
Business Combinations [Abstract]
Business Acquisition, Date of Acquisition Agreement	Jun. 22, 2014
Number of WEC shares per Integrys share	1.128
Cash per share of Integrys common stock	$ 18.58
Total Value of cash and common stock consideration of acquisition	$ 5.4
Estimate of acquisition-related debt	$ 1.5