Regulatory Matters - Summary of Company's and Equity Bank's Capital Amounts and Ratios (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total capital to risk weighted assets, To Be Well Capitalized Under Prompt Corrective Provisions, Actual Ratio	10.00%
Tier 1 capital to risk weighted assets, To Be Well Capitalized Under Prompt Corrective Provisions, Actual Ratio	8.00%
Common equity Tier 1 capital to risk weighted assets, To Be Well Capitalized Under Prompt Corrective Provisions, Actual Ratio	6.50%
Tier 1 leverage to average assets, To Be Well Capitalized Under Prompt Corrective Provisions, Actual Ratio	5.00%
Equity Bancshares, Inc. [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total capital to risk weighted assets, Actual Amount	$ 352,853	$ 337,649
Total capital to risk weighted assets, Actual Ratio	12.59%	11.86%
Tier 1 capital to risk weighted assets, Actual Amount	$ 340,621	$ 326,195
Tier 1 capital to risk weighted assets, Actual Ratio	12.15%	11.45%
Common equity Tier 1 capital to risk weighted assets, Actual Amount	$ 326,060	$ 311,935
Common equity Tier 1 capital to risk weighted assets, Actual Ratio	11.63%	10.95%
Tier 1 leverage to average assets, Actual Amount	$ 340,621	$ 326,195
Tier 1 leverage to average assets, Actual Ratio	9.02%	8.60%
Equity Bank [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total capital to risk weighted assets, Actual Amount	$ 348,951	$ 338,180
Total capital to risk weighted assets, Actual Ratio	12.47%	11.89%
Total capital to risk weighted assets, Minimum Required for Capital Adequacy Purposes, Actual Amount	$ 279,921	$ 284,400
Total capital to risk weighted assets, To Be Well Capitalized Under Prompt Corrective Provisions, Actual Ratio	10.00%	10.00%
Tier 1 capital to risk weighted assets, Actual Amount	$ 336,719	$ 326,726
Tier 1 capital to risk weighted assets, Actual Ratio	12.03%	11.49%
Tier 1 capital to risk weighted assets, To Be Well Capitalized Under Prompt Corrective Provisions, Actual Amount	$ 223,937	$ 227,520
Tier 1 capital to risk weighted assets, To Be Well Capitalized Under Prompt Corrective Provisions, Actual Ratio	8.00%	8.00%
Common equity Tier 1 capital to risk weighted assets, Actual Amount	$ 336,719	$ 326,726
Common equity Tier 1 capital to risk weighted assets, Actual Ratio	12.03%	11.49%
Common equity Tier 1 capital to risk weighted assets, To Be Well Capitalized Under Prompt Corrective Provisions, Actual Amount	$ 181,949	$ 184,860
Common equity Tier 1 capital to risk weighted assets, To Be Well Capitalized Under Prompt Corrective Provisions, Actual Ratio	6.50%	6.50%
Tier 1 leverage to average assets, Actual Amount	$ 336,719	$ 326,726
Tier 1 leverage to average assets, Actual Ratio	8.92%	8.62%
Tier 1 leverage to average assets, To Be Well Capitalized Under Prompt Corrective Provisions, Actual Amount	$ 188,679	$ 189,488
Tier 1 leverage to average assets, To Be Well Capitalized Under Prompt Corrective Provisions, Actual Ratio	5.00%	5.00%
Basel III Phase-In [Member] | Equity Bancshares, Inc. [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total capital to risk weighted assets, Minimum Required for Capital Adequacy Purposes, Actual Amount	$ 294,341	$ 281,222
Total capital to risk weighted assets, Minimum Required for Capital Adequacy Purposes, Actual Ratio	10.50%	9.88%
Tier 1 capital to risk weighted assets, Minimum Required for Capital Adequacy Purposes, Actual Amount	$ 238,276	$ 224,266
Tier 1 capital to risk weighted assets, Minimum Required for Capital Adequacy Purposes, Actual Ratio	8.50%	7.88%
Common equity Tier 1 capital to risk weighted assets, Minimum Required for Capital Adequacy Purposes, Actual Amount	$ 196,227	$ 181,548
Common equity Tier 1 capital to risk weighted assets, Minimum Required for Capital Adequacy Purposes, Actual Ratio	7.00%	6.38%
Tier 1 leverage to average assets, Minimum Required for Capital Adequacy Purposes, Actual Amount	$ 151,072	$ 151,731
Tier 1 leverage to average assets, Minimum Required for Capital Adequacy Purposes, Actual Ratio	4.00%	4.00%
Basel III Phase-In [Member] | Equity Bank [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total capital to risk weighted assets, Minimum Required for Capital Adequacy Purposes, Actual Amount	$ 293,917	$ 280,845
Total capital to risk weighted assets, Minimum Required for Capital Adequacy Purposes, Actual Ratio	10.50%	9.88%
Tier 1 capital to risk weighted assets, Minimum Required for Capital Adequacy Purposes, Actual Amount	$ 237,933	$ 223,965
Tier 1 capital to risk weighted assets, Minimum Required for Capital Adequacy Purposes, Actual Ratio	8.50%	7.88%
Common equity Tier 1 capital to risk weighted assets, Minimum Required for Capital Adequacy Purposes, Actual Amount	$ 195,945	$ 181,305
Common equity Tier 1 capital to risk weighted assets, Minimum Required for Capital Adequacy Purposes, Actual Ratio	7.00%	6.38%
Tier 1 leverage to average assets, Minimum Required for Capital Adequacy Purposes, Actual Amount	$ 150,943	$ 151,590
Tier 1 leverage to average assets, Minimum Required for Capital Adequacy Purposes, Actual Ratio	4.00%	4.00%
Basel III Fully Phased-In [Member] | Equity Bancshares, Inc. [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total capital to risk weighted assets, Minimum Required for Capital Adequacy Purposes, Actual Ratio	10.50%	10.50%
Total capital to risk weighted assets, Minimum Required for Capital Adequacy Purposes, Actual Amount	$ 294,341	$ 299,021
Tier 1 capital to risk weighted assets, Minimum Required for Capital Adequacy Purposes, Actual Amount	$ 238,276	$ 242,065
Tier 1 capital to risk weighted assets, Minimum Required for Capital Adequacy Purposes, Actual Ratio	8.50%	8.50%
Common equity Tier 1 capital to risk weighted assets, Minimum Required for Capital Adequacy Purposes, Actual Amount	$ 196,227	$ 199,347
Common equity Tier 1 capital to risk weighted assets, Minimum Required for Capital Adequacy Purposes, Actual Ratio	7.00%	7.00%
Tier 1 leverage to average assets, Minimum Required for Capital Adequacy Purposes, Actual Amount	$ 151,072	$ 151,731
Tier 1 leverage to average assets, Minimum Required for Capital Adequacy Purposes, Actual Ratio	4.00%	4.00%
Basel III Fully Phased-In [Member] | Equity Bank [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total capital to risk weighted assets, Minimum Required for Capital Adequacy Purposes, Actual Ratio	10.50%	10.50%
Total capital to risk weighted assets, Minimum Required for Capital Adequacy Purposes, Actual Amount	$ 293,917	$ 298,619
Tier 1 capital to risk weighted assets, Minimum Required for Capital Adequacy Purposes, Actual Amount	$ 237,933	$ 241,740
Tier 1 capital to risk weighted assets, Minimum Required for Capital Adequacy Purposes, Actual Ratio	8.50%	8.50%
Common equity Tier 1 capital to risk weighted assets, Minimum Required for Capital Adequacy Purposes, Actual Amount	$ 195,945	$ 199,080
Common equity Tier 1 capital to risk weighted assets, Minimum Required for Capital Adequacy Purposes, Actual Ratio	7.00%	7.00%
Tier 1 leverage to average assets, Minimum Required for Capital Adequacy Purposes, Actual Amount	$ 150,943	$ 151,590
Tier 1 leverage to average assets, Minimum Required for Capital Adequacy Purposes, Actual Ratio	4.00%	4.00%