PENSION AND OTHER SAVING PLANS - Multiemployer Plans (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Jan. 31, 2012
Multiemployer Plans [Line Items]
Multiemployer Plans Funded Status Minimum Percentage				80.00%
WECO [Member]
Multiemployer Plans [Line Items]
Multiemployer Plan Minimum Contribution Per Hour Worked	5.80
Multiemployer Plan Maximum Contribution Per Hour Worked	5.85
Multiemployer Plan, Period Contributions	$ 3.3	$ 3.4	$ 3.2
WRI [Member]
Multiemployer Plans [Line Items]
Multiemployer Plan Minimum Contribution Per Hour Worked	5.70
Multiemployer Plan, Period Contributions	1.2	0.9	0.5
WSC [Member]
Multiemployer Plans [Line Items]
Multiemployer Plan Minimum Contribution Per Hour Worked	3.45
Multiemployer Plan Maximum Contribution Per Hour Worked	4.70
Multiemployer Plan, Period Contributions	$ 0.1	$ 0.1	$ 0.1