SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Tables)

12 Months Ended

Dec. 31, 2019

Accounting Policies [Abstract]

Schedule of inventory

Our inventory as of December 31 consisted of:

(in millions)	2019		2018
Materials and supplies	$	50.1	$	48.9
Fossil fuel	36.1		29.2
Natural gas in storage	20.2		24.9
Total	$	106.4	$	103.0

Schedule of total AFUDC

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

(in millions)	2019		2018		2017
AFUDC – Debt	$	2.4	$	1.9	$	1.6
AFUDC – Equity	5.7		4.6		4.1

Schedule of assumptions 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:

	2019			2018			2017
Stock options granted	21,638			21,265			23,300
Estimated weighted-average fair value per stock option	$	8.60		$	7.68		$	7.53
Assumptions used to value the options:
Risk-free interest rate	2.5% – 2.7%			1.6% – 2.5%			0.7% – 2.5%
Dividend yield	3.6		%	3.5		%	3.5		%
Expected volatility	17.0		%	18.0		%	19.0		%
Expected life (years)	8.5			5.8			6.9