SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES EMPLOYEE BENEFITS (Details)	12 Months Ended
	Dec. 31, 2014
Employee benefits
Recognition period for transition obligation to other postretirement benefit plans that existed prior to the merger	20 years
WPS
Employee benefits
Recognition period for changes in realized and unrealized investment gains and losses	5 years
IBS and PELLC
Employee benefits
Recognition period for differences between actual investment returns and expected return on plan assets	5 years