INCOME TAXES (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Current income tax provision (benefit)
Federal	$ (1,568)	$ 20,129	$ 24,537
State	(1,565)	2,965	5,008
Total current income tax provision (benefit)	(3,133)	23,094	29,545
Deferred income tax provision
Federal	37,810	10,757	8,375
State	5,639	7,728	4,932
Total deferred income tax provision	43,449	18,485	13,307
Income Tax Reconciliation [Abstract]
Income before income taxes	$ 246,750	$ 237,991	$ 229,601
Federal Statutory Income Tax Rate	21.00%	21.00%	21.00%
Provision for federal income taxes	$ 51,817	$ 49,978	$ 48,215
State income taxes, net of federal benefit	4,074	10,693	9,758
Amortization of EDIT regulatory liability	(17,289)	(17,031)	(12,828)
Effective Income Tax Rate Reconciliation, tax benefit of employee share based compensation	(469)	(1,489)	(2,116)
Other, net	2,183	(572)	(177)
Income tax provision	40,316	41,579	$ 42,852
Deferred tax assets
Deferred tax assets, employee benefits and other accrued liabilities	11,126	28,127
Deferred tax asset, regulatory adjustments	120,051	121,738
Net operating loss	424,861	0
Deferred Tax Assets, Leasing Arrangements	6,906	9,319
Other	12,597	4,790
Total deferred tax assets	575,541	163,974
Deferred tax liabilities
Excess of tax over book depreciation	734,051	717,492
Purchased-gas cost adjustment - winter weather event	421,070	0
Purchased-gas cost adjustment - other	37,433	5,240
Other regulatory assets and liabilities, net	71,541	88,260
Deferred Tax Liabilities, Leasing Arrangements	6,730	9,788
Total deferred tax liabilities	1,270,825	820,780
Net deferred tax liabilities	695,284	$ 656,806
Reduction in ADIT recorded as an EDIT regulatory liability associated with reduction of Oklahoma state income tax	29,300
Kansas Gas Service tax reform regulatory liability	84,200
Reduction to base rates due to Kansas Gas Service tax reform regulatory liability	4,900
Deferred Tax Liabilities, Regulatory Assets and Liabilities - Winter Storm Uri	421,100
Domestic Tax Authority
Deferred tax assets
Net operating loss	386,000
State and Local Jurisdiction
Deferred tax assets
Net operating loss	$ 38,900