Derivative Instruments (Tables)

6 Months Ended

Jun. 30, 2014

Derivative Instruments (Tables) [Abstract]

Derivative instruments in balance sheet

	June 30, 2014				December 31, 2013
	Derivative Asset		Derivative Liability		Derivative Asset		Derivative Liability
	(Millions of Dollars)
Natural Gas	$	7.4	$	—	$	5.6	$	0.1
Fuel Oil	0.2		—		0.6		—
FTRs	14.1		—		3.5		—
Coal	1.2		0.2		2.1		0.2
Total	$	22.9	$	0.2	$	11.8	$	0.3

Derivative instruments' estimated notional volumes and gain (losses)

	Three Months Ended June 30, 2014			Three Months Ended June 30, 2013
	Volume	Gains (Losses)		Volume	Gains (Losses)
		(Millions of Dollars)			(Millions of Dollars)
Natural Gas	9.9 million Dth	$	2.5	11.3 million Dth	$	1.9
Fuel Oil	2.4 million gallons	0.4		2.2 million gallons	0.1
FTRs	7.4 million MWh	2.6		6.5 million MWh	4.7
Total		$	5.5		$	6.7

	Six Months Ended June 30, 2014			Six Months Ended June 30, 2013
	Volume	Gains (Losses)		Volume	Gains (Losses)
		(Millions of Dollars)			(Millions of Dollars)
Natural Gas	24.8 million Dth	$	10.1	30.1 million Dth	$	(4.6	)
Fuel Oil	4.4 million gallons	0.6		3.7 million gallons	0.2
FTRs	13.1 million MWh	9.6		12.3 million MWh	5.6
Total		$	20.3		$	1.2

Offsetting Assets and Liabilities [Table Text Block]

	June 30, 2014				December 31, 2013
	Derivative		Derivative		Derivative		Derivative
	Asset		Liability		Asset		Liability
	(Millions of Dollars)
Gross Amount Recognized on the Balance Sheet	$	22.9	$	0.2	$	11.8	$	0.3
Gross Amount Not Offset on Balance Sheet (a)	—		—		—		—
Net Amount	$	22.9	$	0.2	$	11.8	$	0.3

(a) Gross Amount Not Offset on Balance Sheet includes no cash collateral posted as of June 30, 2014 and December 31, 2013.