PARENT COMPANY ONLY CONDENSED FINANCIAL INFORMATION, Condensed Statements of Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Cash flows from operating activities [Abstract]
Net income	$ 45,353	$ 29,220
Adjustments [Abstract]
Stock based compensation	1,272	853
Net cash from operating activities	5,627	30,484
Cash flows from investing activities [Abstract]
Cash paid in business combination	(687)	0
Net cash from investing activities	(156,228)	(213,493)
Cash flows from financing activities [Abstract]
Issuance of common stock	0	51,392
Payments to tax authorities for stock-based compensation	(319)	(351)
Payments to repurchase common stock	(293)	0
Cash dividends on common stock	(2,528)	(1,079)
Net cash from financing activities	292,809	95,119
Net change in cash and cash equivalents	142,208	(87,890)
Beginning cash and cash equivalents	158,099	245,989
Ending cash and cash equivalents	300,307	158,099
South Plains Financial, Inc. [Member]
Cash flows from operating activities [Abstract]
Net income	45,353	29,220
Adjustments [Abstract]
Equity in undistributed subsidiary income	(28,682)	(25,241)
Amortization of debt issuance costs	47	0
Stock based compensation	1,272	853
Change in other assets	(342)	(1,601)
Change in other liabilities	131	541
Release of unearned ESOP shares	0	0
Net cash from operating activities	17,779	3,772
Cash flows from investing activities [Abstract]
Cash paid in business combination	0	(76,100)
Net cash from investing activities	0	(76,100)
Cash flows from financing activities [Abstract]
Proceeds from long-term borrowings	49,070	0
Repayments of long-term borrowings	0	(7,530)
Issuance of common stock	0	51,392
Payments to tax authorities for stock-based compensation	(319)	(351)
Payments to repurchase common stock	(293)	0
Share based liability conversion	0	11,450
Cash dividends on common stock	(2,528)	(1,079)
Net cash from financing activities	45,930	53,882
Net change in cash and cash equivalents	63,709	(18,446)
Beginning cash and cash equivalents	4,181	22,627
Ending cash and cash equivalents	$ 67,890	$ 4,181