COMMON EQUITY (Details 4) (USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2013
Capital Transactions with Subsidiaries
Dividends to parent	$ 134.2
Return of capital to parent	74.0
Equity contributions from parent	243.9
WPS Investments, LLC
Capital Transactions with Subsidiaries
Ownership interest (as a percent)	86.13%
ITF
Capital Transactions with Subsidiaries
Dividends to parent	0
Return of capital to parent	0
Equity contributions from parent	25.2
MERC
Capital Transactions with Subsidiaries
Dividends to parent	0
Return of capital to parent	21.0
Equity contributions from parent	3.5
MGU
Capital Transactions with Subsidiaries
Dividends to parent	0
Return of capital to parent	12.5
Equity contributions from parent	5.0
UPPCO
Capital Transactions with Subsidiaries
Dividends to parent	0
Return of capital to parent	5.5
Equity contributions from parent	0
UPPCO | WPS Investments, LLC
Capital Transactions with Subsidiaries
Ownership interest (as a percent)	2.43%
WPS
Capital Transactions with Subsidiaries
Dividends to parent	81.5
Return of capital to parent	35.0
Equity contributions from parent	200.0
WPS | WPS Investments, LLC
Capital Transactions with Subsidiaries
Ownership interest (as a percent)	11.44%
WPS Investments, LLC
Capital Transactions with Subsidiaries
Dividends to parent	52.7
Return of capital to parent	0
Equity contributions from parent	$ 10.2