SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Tables)

12 Months Ended

Dec. 31, 2017

Accounting Policies [Abstract]

Schedule of inventory

Our inventory as of December 31 consisted of:

(in millions)	2017		2016
Fossil fuel	$	43.8	$	66.7
Materials and supplies	40.8		37.5
Natural gas in storage	22.4		21.1
Total	$	107.0	$	125.3

Schedule of total AFUDC

We recorded the following AFUDC for the years ended December 31:

(in millions)	2017		2016		2015
AFUDC – Debt	$	1.6	$	8.1	$	6.1
AFUDC – Equity	4.1		19.5		15.1

Schedule of assumption used to estimate the fair value of stock options granted

The following table shows the estimated weighted-average fair value per stock option granted to our employees along with the weighted-average assumptions used in the valuation models:

	2017			2016
Stock options granted	23,300			24,485
Estimated weighted-average fair value per stock option	$	7.53		$	5.63
Assumptions used to value the options:
Risk-free interest rate	0.7% – 2.5%			0.4% – 1.8%
Dividend yield	3.5		%	4.0		%
Expected volatility	19.0		%	18.0		%
Expected life (years)	6.9			7.5