Regulatory Assets and Liabilities (Tables)

12 Months Ended

Dec. 31, 2014

Regulatory Assets and Liabilities Disclosure [Abstract]

Schedule of Regulatory Assets [Table Text Block]

The regulatory assets and regulatory liabilities resulting from our application of the provisions of ASC Topic 980, Regulated Operations, included in the accompanying Consolidated Balance Sheet at December 31, 2014 and December 31, 2013 are as follows (in millions):

Regulatory Assets	2014		2013
Grossed-up deferred taxes on equity funds used during construction	$	78.4	$	80.6
Asset retirement obligations	115.9		128.5
Asset retirement costs - Eminence	63.2		68.2
Deferred taxes	7.0		8.1
Deferred cash out	12.9		—
Deferred gas costs	8.7		6.2
Fuel cost	29.2		0.7
Other	1.6		1.8
Total Regulatory Assets	$	316.9	$	294.1

Schedule of Regulatory Liabilities [Table Text Block]

Regulatory Liabilities	2014		2013
Negative salvage	$	283.8	$	241.7
Deferred cash out	—		1.6
Sentinel meter station depreciation	5.8		5.0
Postretirement benefits other than pension	39.1		25.3
Electric power cost	4.4		13.8
Other	—		0.2
Total Regulatory Liabilities	$	333.1	$	287.6