SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2021	Dec. 31, 2020
Loans [Abstract]
Number of days principal or interest payments are past due for loans to be placed on nonaccrual status	90 days
Goodwill and Other Intangible Assets [Abstract]
Impairment loss	$ 0	$ 0
Minimum [Member]
Allowance for Loan Losses [Abstract]
Threshold balance of loan to be specifically reviewed for impairment	$ 250
City Bank [Member] | Bank Subsidiary [Member]
Subsidiaries Information [Abstract]
Wholly Owned, Consolidated Subsidiaries	City Bank
Windmark Insurance Agency, Inc. ("Windmark") [Member] | Non-bank Subsidiary [Member]
Subsidiaries Information [Abstract]
Wholly Owned, Consolidated Subsidiaries	Windmark Insurance Agency, Inc. ("Windmark")
Ruidoso Retail, Inc. [Member] | Non-bank Subsidiary [Member]
Subsidiaries Information [Abstract]
Wholly Owned, Consolidated Subsidiaries	Ruidoso Retail, Inc.
CB Provence, LLC [Member] | Non-bank Subsidiary [Member]
Subsidiaries Information [Abstract]
Wholly Owned, Consolidated Subsidiaries	CB Provence, LLC
CBT Brushy Creek, LLC [Member] | Non-bank Subsidiary [Member]
Subsidiaries Information [Abstract]
Wholly Owned, Consolidated Subsidiaries	CBT Brushy Creek, LLC
CBT Properties, LLC [Member] | Non-bank Subsidiary [Member]
Subsidiaries Information [Abstract]
Wholly Owned, Consolidated Subsidiaries	CBT Properties, LLC
South Plains Financial Capital Trusts (SPFCT) III-V [Member] | Non-bank Subsidiary [Member]
Subsidiaries Information [Abstract]
Wholly Owned, Equity Method Subsidiaries	South Plains Financial Capital Trusts (SPFCT) III-V
Substandard or Worse [Member] | Minimum [Member]
Allowance for Loan Losses [Abstract]
Threshold balance of loan to be specifically reviewed for impairment	$ 250
Customer Relationships [Member]
Goodwill and Other Intangible Assets [Abstract]
Estimated useful lives	5 years
Employment Agreements [Member]
Goodwill and Other Intangible Assets [Abstract]
Estimated useful lives	5 years
Core Deposits Intangible [Member] | Maximum [Member]
Goodwill and Other Intangible Assets [Abstract]
Estimated useful lives	10 years