Regulatory Matters - Summary of Company's and Equity Bank's Capital Amounts and Ratios (Detail) $ in Thousands	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
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	0.10
Tier 1 capital to risk weighted assets, To Be Well Capitalized Under Prompt Corrective Provisions, Actual Ratio	0.08
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	0.05
Equity Bancshares, Inc. [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total capital to risk weighted assets, Actual Amount	$ 462,865	$ 352,853
Total capital to risk weighted assets, Actual Ratio	0.1735	12.59
Tier 1 capital to risk weighted assets, Actual Amount	$ 356,707	$ 340,621
Tier 1 capital to risk weighted assets, Actual Ratio	0.1337	0.1215
Tier 1 capital to risk weighted assets, Minimum Required for Capital Adequacy Purposes, Actual Amount		$ 238,276
Common equity Tier 1 capital to risk weighted assets, Actual Amount	$ 341,835	$ 326,060
Common equity Tier 1 capital to risk weighted assets, Actual Ratio	0.1282	0.1163
Tier 1 leverage to average assets, Actual Amount	$ 356,707	$ 340,621
Tier 1 leverage to average assets, Actual Ratio	0.0930	0.0902
Tier 1 leverage to average assets, Minimum Required for Capital Adequacy Purposes, Actual Amount		$ 151,072
Equity Bank [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total capital to risk weighted assets, Actual Amount	$ 418,992	$ 348,951
Total capital to risk weighted assets, Actual Ratio	0.1573	12.47
Total capital to risk weighted assets, To Be Well Capitalized Under Prompt Corrective Provisions, Actual Amount	$ 266,329	$ 279,921
Total capital to risk weighted assets, To Be Well Capitalized Under Prompt Corrective Provisions, Actual Ratio	0.1000	10.00
Tier 1 capital to risk weighted assets, Actual Amount	$ 385,696	$ 336,719
Tier 1 capital to risk weighted assets, Actual Ratio	0.1448	0.1203
Tier 1 capital to risk weighted assets, Minimum Required for Capital Adequacy Purposes, Actual Amount		$ 237,933
Tier 1 capital to risk weighted assets, To Be Well Capitalized Under Prompt Corrective Provisions, Actual Amount	$ 213,064
Tier 1 capital to risk weighted assets, To Be Well Capitalized Under Prompt Corrective Provisions, Actual Ratio	0.0800	0.0800
Common equity Tier 1 capital to risk weighted assets, Actual Amount	$ 385,696	$ 336,719
Common equity Tier 1 capital to risk weighted assets, Actual Ratio	0.1448	0.1203
Common equity Tier 1 capital to risk weighted assets, To Be Well Capitalized Under Prompt Corrective Provisions, Actual Amount	$ 173,114	$ 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	$ 385,696	$ 336,719
Tier 1 leverage to average assets, Actual Ratio	0.1007	0.0892
Tier 1 leverage to average assets, Minimum Required for Capital Adequacy Purposes, Actual Amount		$ 150,943
Tier 1 leverage to average assets, To Be Well Capitalized Under Prompt Corrective Provisions, Actual Amount	$ 191,595
Tier 1 leverage to average assets, To Be Well Capitalized Under Prompt Corrective Provisions, Actual Ratio	0.0500	0.0500
Base 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	$ 280,072	$ 294,341
Total capital to risk weighted assets, Minimum Required for Capital Adequacy Purposes, Actual Ratio	0.1050	0.1050
Tier 1 capital to risk weighted assets, Minimum Required for Capital Adequacy Purposes, Actual Amount	$ 226,725
Tier 1 capital to risk weighted assets, Minimum Required for Capital Adequacy Purposes, Actual Ratio	0.0850	0.0850
Common equity Tier 1 capital to risk weighted assets, Minimum Required for Capital Adequacy Purposes, Actual Amount	$ 186,714	$ 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 Amount	$ 153,490
Tier 1 leverage to average assets, Minimum Required for Capital Adequacy Purposes, Actual Ratio	0.0400	0.0400
Base 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	$ 279,646	$ 293,917
Total capital to risk weighted assets, Minimum Required for Capital Adequacy Purposes, Actual Ratio	0.1050	0.1050
Tier 1 capital to risk weighted assets, Minimum Required for Capital Adequacy Purposes, Actual Amount	$ 226,380
Tier 1 capital to risk weighted assets, Minimum Required for Capital Adequacy Purposes, Actual Ratio	0.0850	0.0850
Tier 1 capital to risk weighted assets, To Be Well Capitalized Under Prompt Corrective Provisions, Actual Amount		$ 223,937
Common equity Tier 1 capital to risk weighted assets, Minimum Required for Capital Adequacy Purposes, Actual Amount	$ 186,431	$ 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 Amount	$ 153,276
Tier 1 leverage to average assets, Minimum Required for Capital Adequacy Purposes, Actual Ratio	0.0400	0.0400
Tier 1 leverage to average assets, To Be Well Capitalized Under Prompt Corrective Provisions, Actual Amount		$ 188,679