Rate Matters Rate Matters, NSP-WI (Details) (PSCW Proceeding - Wisconsin Electric Rate Case 2015 [Member], NSP-Wisconsin, USD $)	1 Months Ended
	May 31, 2014	Oct. 31, 2014 Subsequent Event Public Service Commission of Wisconsin (PSCW) [Member]
NSP-WI 2015 Electric Rate Case [Line Items]
Public Utilities, amount requested by public utility related to production and transmission fixed charges	$ 28,100,000
Public Utilities, Adjustment to requested rate increase (decrease) recommended by third parties, related to production and transmission fixed charges		26,400,000
Public Utilities, Requested Rate Increase (Decrease), Amount	20,600,000
Public Utilities, Requested Rate Increase (Decrease), Percentage	3.20%
Public Utilities, Requested Return on Equity, Percentage	10.20%
Public Utilities, percentage of earnings above the authorized ROE that will be refunded to customers	100.00%
Public Utilities, amount requested by public utility related to fuel and purchased power	13,900,000
Public Utilities, Adjustment to requested rate increase (decrease) related to fuel and purchased power		11,100,000
Public Utilities, requested base revenue increase (decrease) excluding NSP-Minnesota depreciation reserve and Monticello EPU deferral adjustments	42,000,000
Public Utilities, Adjustment to base revenue increase (decrease) recommended by third parties excluding NSP-Minnesota depreciation reserve and Monticello EPU deferrals		37,500,000
Public Utilities, Adjustment to requested rate increase (decrease) related to the NSP-Minnesota transmission depreciation reserve	(16,200,000)
Public Utilities, Adjustment to requested rate increase (decrease) recommended by third parties related to the NSP-Minnesota transmission depreciation reserve		(16,200,000)
Public Utilities, Adjustment to requested rate increase (decrease) related to the Monticello EPU deferral	(5,200,000)
Public Utilities, Adjustment to requested rate increase (decrease) recommended by third parties related to Monticello EPU depreciation deferrals		(5,200,000)
Public Utilities, Rate increase (decrease) recommended by third parties		16,100,000
Public utilities, Adjustment to requested rate increase (decrease) recommended by third parties, percentage		2.50%
The rate increase (decrease) requested of a regulatory body through an agreement between a public utility and another party or parties		$ 16,100,000