COMMON EQUITY (Details 5) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013
Capital Transactions with Subsidiaries
Dividends to parent	$ 191.6
Return of capital to parent	75.0
Equity contributions from parent	278.9
ITF
Capital Transactions with Subsidiaries
Dividends to parent	0
Return of capital to parent	0
Equity contributions from parent	44.3
MERC
Capital Transactions with Subsidiaries
Dividends to parent	0
Return of capital to parent	21.0
Equity contributions from parent	13.0
MGU
Capital Transactions with Subsidiaries
Dividends to parent	0
Return of capital to parent	12.5
Equity contributions from parent	8.0
NSG
Capital Transactions with Subsidiaries
Dividends to parent	12.0
Return of capital to parent	0
Equity contributions from parent	0
UPPCO
Capital Transactions with Subsidiaries
Dividends to parent	0
Return of capital to parent	6.5
Equity contributions from parent	0
WPS
Capital Transactions with Subsidiaries
Dividends to parent	108.6
Return of capital to parent	35.0
Equity contributions from parent	200.0
WPS Investments, LLC
Capital Transactions with Subsidiaries
Dividends to parent	71.0
Return of capital to parent	0
Equity contributions from parent	$ 13.6
WPS Investments, LLC
Capital Transactions with Subsidiaries
Ownership interest (as a percent)	86.22%
WPS Investments, LLC | UPPCO
Capital Transactions with Subsidiaries
Ownership interest (as a percent)	2.42%
WPS Investments, LLC | WPS
Capital Transactions with Subsidiaries
Ownership interest (as a percent)	11.36%