Regulatory Assets and Liabilities (Tables)

12 Months Ended

Dec. 31, 2015

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, 2015 and December 31, 2014 are as follows (in millions):

Regulatory Assets	2015		2014
Grossed-up deferred taxes on equity funds used during construction	$	75.8	$	78.4
Asset retirement obligations	113.5		115.9
Asset retirement costs - Eminence	58.8		63.2
Deferred taxes	5.9		7.0
Deferred cash out	43.9		12.9
Deferred gas costs	—		8.7
Fuel cost	43.8		29.2
Other	1.6		1.6
Total Regulatory Assets	$	343.3	$	316.9

Schedule of Regulatory Liabilities [Table Text Block]

Regulatory Liabilities	2015		2014
Negative salvage	$	318.3	$	283.8
Sentinel meter station depreciation	6.0		5.8
Postretirement benefits other than pension	51.0		39.1
Electric power cost	0.8		4.4
Pension - deferred collections	8.0		—
Other	1.8		—
Total Regulatory Liabilities	$	385.9	$	333.1