LOANS AND ALLOWANCE FOR CREDIT LOSSES - Aging Analysis of the Recorded Investment in Past Due Loans (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Accounts Notes And Loans Receivable [Line Items]
Loans	$ 4,283,514	$ 4,220,486
Nonaccrual Loans	26,275	24,127
30-89 Days
Accounts Notes And Loans Receivable [Line Items]
Loans	18,149	13,782
90 or More Days
Accounts Notes And Loans Receivable [Line Items]
Loans	0	0
Total Past Due Loans
Accounts Notes And Loans Receivable [Line Items]
Loans	18,149	13,782
Current Loans
Accounts Notes And Loans Receivable [Line Items]
Loans	4,239,090	4,182,577
Commercial and industrial
Accounts Notes And Loans Receivable [Line Items]
Loans	714,450	693,559
Nonaccrual Loans	7,809	8,358
Commercial and industrial \| 30-89 Days
Accounts Notes And Loans Receivable [Line Items]
Loans	3,149	1,786
Commercial and industrial \| 90 or More Days
Accounts Notes And Loans Receivable [Line Items]
Loans	0	0
Commercial and industrial \| Total Past Due Loans
Accounts Notes And Loans Receivable [Line Items]
Loans	3,149	1,786
Commercial and industrial \| Current Loans
Accounts Notes And Loans Receivable [Line Items]
Loans	703,492	683,415
Paycheck Protection Program (PPP)
Accounts Notes And Loans Receivable [Line Items]
Loans	78,624	145,942
Nonaccrual Loans	0	0
Paycheck Protection Program (PPP) \| 30-89 Days
Accounts Notes And Loans Receivable [Line Items]
Loans	0	0
Paycheck Protection Program (PPP) \| 90 or More Days
Accounts Notes And Loans Receivable [Line Items]
Loans	0	0
Paycheck Protection Program (PPP) \| Total Past Due Loans
Accounts Notes And Loans Receivable [Line Items]
Loans	0	0
Paycheck Protection Program (PPP) \| Current Loans
Accounts Notes And Loans Receivable [Line Items]
Loans	78,624	145,942
Real estate: \| Commercial real estate (including multi-family residential)
Accounts Notes And Loans Receivable [Line Items]
Loans	2,197,502	2,104,621
Nonaccrual Loans	15,259	12,639
Real estate: \| Commercial real estate (including multi-family residential) \| 30-89 Days
Accounts Notes And Loans Receivable [Line Items]
Loans	8,391	7,689
Real estate: \| Commercial real estate (including multi-family residential) \| 90 or More Days
Accounts Notes And Loans Receivable [Line Items]
Loans	0	0
Real estate: \| Commercial real estate (including multi-family residential) \| Total Past Due Loans
Accounts Notes And Loans Receivable [Line Items]
Loans	8,391	7,689
Real estate: \| Commercial real estate (including multi-family residential) \| Current Loans
Accounts Notes And Loans Receivable [Line Items]
Loans	2,173,852	2,084,293
Real estate: \| Commercial real estate construction and land development
Accounts Notes And Loans Receivable [Line Items]
Loans	453,473	439,125
Nonaccrual Loans	0	63
Real estate: \| Commercial real estate construction and land development \| 30-89 Days
Accounts Notes And Loans Receivable [Line Items]
Loans	2,611	619
Real estate: \| Commercial real estate construction and land development \| 90 or More Days
Accounts Notes And Loans Receivable [Line Items]
Loans	0	0
Real estate: \| Commercial real estate construction and land development \| Total Past Due Loans
Accounts Notes And Loans Receivable [Line Items]
Loans	2,611	619
Real estate: \| Commercial real estate construction and land development \| Current Loans
Accounts Notes And Loans Receivable [Line Items]
Loans	450,862	438,443
Real estate: \| 1-4 family residential (including home equity)
Accounts Notes And Loans Receivable [Line Items]
Loans	669,306	685,071
Nonaccrual Loans	3,065	2,875
Real estate: \| 1-4 family residential (including home equity) \| 30-89 Days
Accounts Notes And Loans Receivable [Line Items]
Loans	1,539	2,422
Real estate: \| 1-4 family residential (including home equity) \| 90 or More Days
Accounts Notes And Loans Receivable [Line Items]
Loans	0	0
Real estate: \| 1-4 family residential (including home equity) \| Total Past Due Loans
Accounts Notes And Loans Receivable [Line Items]
Loans	1,539	2,422
Real estate: \| 1-4 family residential (including home equity) \| Current Loans
Accounts Notes And Loans Receivable [Line Items]
Loans	664,702	679,774
Real estate: \| Residential construction
Accounts Notes And Loans Receivable [Line Items]
Loans	136,760	117,901
Nonaccrual Loans	0	0
Real estate: \| Residential construction \| 30-89 Days
Accounts Notes And Loans Receivable [Line Items]
Loans	2,431	1,243
Real estate: \| Residential construction \| 90 or More Days
Accounts Notes And Loans Receivable [Line Items]
Loans	0	0
Real estate: \| Residential construction \| Total Past Due Loans
Accounts Notes And Loans Receivable [Line Items]
Loans	2,431	1,243
Real estate: \| Residential construction \| Current Loans
Accounts Notes And Loans Receivable [Line Items]
Loans	134,329	116,658
Consumer and other
Accounts Notes And Loans Receivable [Line Items]
Loans	33,399	34,267
Nonaccrual Loans	142	192
Consumer and other \| 30-89 Days
Accounts Notes And Loans Receivable [Line Items]
Loans	28	23
Consumer and other \| 90 or More Days
Accounts Notes And Loans Receivable [Line Items]
Loans	0	0
Consumer and other \| Total Past Due Loans
Accounts Notes And Loans Receivable [Line Items]
Loans	28	23
Consumer and other \| Current Loans
Accounts Notes And Loans Receivable [Line Items]
Loans	$ 33,229	$ 34,052

Allegiance Bancshares, Inc. 10-Q