COMMON STOCK: Common Stock, Number of Shares, Par Value and Other Disclosures (Details) - shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Class of Stock [Line Items]
Common Stock, Shares, Issued	50,420,017	50,420,017	50,420,017
Shares issued during the year	0
Common Stock, Shares, Issued	50,420,017	50,420,017	50,420,017
Continuous equity program (inactive)
Class of Stock [Line Items]
Shares issued during the year	0	0	0
Shares reserved for future issuance	3,000,000
Dividend reinvestment and stock purchase plan
Class of Stock [Line Items]
Shares issued during the year	0	0	0
Shares reserved for future issuance	2,576,723
Employee savings plan
Class of Stock [Line Items]
Shares issued during the year	0	0	0
Shares reserved for future issuance	3,567,954
Long-term incentive and compensation plan
Class of Stock [Line Items]
Shares issued during the year	0	0	0
Shares reserved for future issuance	1,356,729