BENEFIT PLANS: Benefit Plans Narrative (Details) - USD ($)	11 Months Ended	12 Months Ended
	Dec. 31, 2091	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019		Dec. 31, 2018		Dec. 31, 2017
Defined Benefit Plan, Net Periodic Benefit Cost
Net periodic benefit cost					$ 10,976,000		$ 15,781,000	[1]	$ 11,194,000
Period over which bond allocations are to cover benefit payments					5 years
Period over which current rate-of-return is lower than historical					20 years
Fair Value, All Levels Transfers, Amount					$ 0		0
Defined Contribution Plan, Matching Contributions					7,700,000		7,700,000		7,400,000
Pension Plan
Defined Benefit Plan Disclosure
Fair value of plan assets					763,119,000		650,604,000		697,683,000
Defined Benefit Plan, Net Periodic Benefit Cost
Net periodic benefit cost					41,320,000		37,931,000		40,779,000
Amortization of net loss					(13,564,000)		(13,558,000)		(13,190,000)
Amortization of prior service cost					$ 6,000		$ 6,000		$ 28,000
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate					4.55%		3.95%		4.45%
Senior Management Security Plan
Defined Benefit Plan Disclosure
Fair value of plan assets					$ 0		$ 0		$ 0
Executive Deferred Compensation Plan Assets					97,600,000		92,500,000
Defined Benefit Plan, Net Periodic Benefit Cost
Net periodic benefit cost					7,023,000		7,818,000		8,164,000
Amortization of net loss					(2,533,000)		(3,788,000)		(2,963,000)
Amortization of prior service cost					$ 96,000		$ 98,000		$ 127,000
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate					4.60%		3.95%		4.45%
Postretirement Benefits
Defined Benefit Plan Disclosure
Fair value of plan assets					$ 39,625,000	[2]	$ 33,391,000	[2]	$ 38,294,000
Postretirement Benefit, Medical Trend Rate					6.70%		6.30%		6.80%
Postretirement Benefit, Dental Trend Rate					4.00%		4.00%		4.00%
Defined Benefit Plan, Net Periodic Benefit Cost
Net periodic benefit cost					$ 1,670,000		$ 5,490,000		$ 1,496,000
Amortization of prior service cost					$ 48,000		$ 47,000		$ 47,000
Health Care Cost Trend Rate Assumed for Next Fiscal Year					4.00%		4.00%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate					4.60%		3.95%		4.45%
Post-employment Benefits [Member]
Defined Benefit Plan, Net Periodic Benefit Cost
Post employment Benefits Liability					$ 2,000,000		$ 2,000,000
Forecast [Member] | Pension Plan
Defined Benefit Plan, Net Periodic Benefit Cost
Defined Benefit Plan, Minimum Funding Requirement for Next Fiscal Year				$ 14,000,000
Defined Benefit Plan, Estimated Future Employer Contributions in Next Fiscal Year				$ 40,000,000
Forecast [Member] | Postretirement Benefits
Defined Benefit Plan Disclosure
Postretirement Benefit, Dental Trend Rate			4.00%
Defined Benefit Plan, Net Periodic Benefit Cost
Health Care Cost Trend Rate Assumed For Year Two				5.90%
Health Care Cost Trend Rate Assumed for Year Three			5.20%
Health Care Cost Trend Rate Assumed for Year Four	3.90%	5.10%

[1] The 2018 pension and postretirement non-service costs includes $4.2 million of expense for a temporary deviation from the cost-sharing provisions of the substantive postretirement plan as described in Note 12 - "Benefit Plans."

[2] The postretirement benefits assets are primarily life insurance contracts.