Regulatory Matters - Summary of Company's and Equity Bank's Capital Amounts and Ratios (Detail) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
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	$ 358,508	$ 352,853
Total capital to risk weighted assets, Actual Ratio	13.00%	12.59%
Tier 1 capital to risk weighted assets, Actual Amount	$ 336,593	$ 340,621
Tier 1 capital to risk weighted assets, Actual Ratio	12.20%	12.15%
Common equity Tier 1 capital to risk weighted assets, Actual Amount	$ 321,955	$ 326,060
Common equity Tier 1 capital to risk weighted assets, Actual Ratio	11.67%	11.63%
Tier 1 leverage to average assets, Actual Amount	$ 336,593	$ 340,621
Tier 1 leverage to average assets, Actual Ratio	9.02%	9.02%
Tier 1 leverage to average assets, Minimum Required for Capital Adequacy Purposes, Actual Amount	$ 149,189	$ 151,072
Equity Bancshares, Inc. [Member] | Base III Phase-In [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	$ 289,637	$ 294,341
Total capital to risk weighted assets, Minimum Required for Capital Adequacy Purposes, Actual Ratio	10.50%	10.50%
Tier 1 capital to risk weighted assets, Minimum Required for Capital Adequacy Purposes, Actual Amount	$ 234,468	$ 238,276
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	$ 193,091	$ 196,227
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 Ratio	4.00%	4.00%
Equity Bank [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total capital to risk weighted assets, Actual Amount	$ 371,955	$ 348,951
Total capital to risk weighted assets, Actual Ratio	13.50%	12.47%
Total capital to risk weighted assets, Minimum Required for Capital Adequacy Purposes, Actual Amount	$ 275,445	$ 279,921
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	$ 350,040	$ 336,719
Tier 1 capital to risk weighted assets, Actual Ratio	12.71%	12.03%
Tier 1 capital to risk weighted assets, To Be Well Capitalized Under Prompt Corrective Provisions, Actual Amount	$ 220,356	$ 223,937
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	$ 350,040	$ 336,719
Common equity Tier 1 capital to risk weighted assets, Actual Ratio	12.71%	12.03%
Common equity Tier 1 capital to risk weighted assets, To Be Well Capitalized Under Prompt Corrective Provisions, Actual Amount	$ 179,039	$ 181,949
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	$ 350,040	$ 336,719
Tier 1 leverage to average assets, Actual Ratio	9.39%	8.92%
Tier 1 leverage to average assets, Minimum Required for Capital Adequacy Purposes, Actual Amount	$ 149,049	$ 150,943
Tier 1 leverage to average assets, To Be Well Capitalized Under Prompt Corrective Provisions, Actual Ratio	5.00%	5.00%
Equity Bank [Member] | Base III Phase-In [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	$ 289,217	$ 293,917
Total capital to risk weighted assets, Minimum Required for Capital Adequacy Purposes, Actual Ratio	10.50%	10.50%
Tier 1 capital to risk weighted assets, Minimum Required for Capital Adequacy Purposes, Actual Amount	$ 234,128	$ 237,933
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	$ 192,811	$ 195,945
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 Ratio	4.00%	4.00%
Tier 1 leverage to average assets, To Be Well Capitalized Under Prompt Corrective Provisions, Actual Amount	$ 186,312	$ 188,679