Condensed Financial Information (Parent Company Only) - Condensed Statement of Cash Flows (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash flows from operating activities
Net income	$ 25,579	$ 35,825	$ 20,649
Adjustments to reconcile net income to net cash from operating activities:
Stock based compensation	2,870	2,509	1,100
Net amortization of purchase valuation adjustments	(4,360)	(5,586)	(4,518)
Net change in:
Other assets	(3,823)	(5,738)	(673)
Interest payable and other liabilities	(299)	1,259	433
Net cash provided by operating activities	48,521	36,666	27,628
Cash flows (to) from investing activities
Proceeds from sale of other real estate owned	1,803	4,730	5,461
Net cash (used in) provided by investing activities	96,101	(171,488)	(222,924)
Cash flows (to) from financing activities
Borrowings on bank stock loan	7,209	22,500	2,500
Principal repayments on bank stock loan	(13,669)	(9,550)	(1,000)
Proceeds from exercise of employee stock options	371	133	1,215
Principal payments on employee stock loan	44		121
Proceeds from employee stock purchase plan	405
Net cash provided by (used in) financing activities	(248,149)	275,445	212,396
Net change in cash and cash equivalents	(103,527)	140,623	17,100
Cash and cash equivalents, beginning of period	192,818	52,195	35,095
Ending cash and cash equivalents	89,291	192,818	52,195
Equity Bancshares, Inc. [Member]
Cash flows from operating activities
Net income	25,579	35,825	20,649
Adjustments to reconcile net income to net cash from operating activities:
Stock based compensation	2,870	2,509	1,100
Equity in undistributed (income) loss	(5,978)	(9,681)	(5,370)
Net amortization of purchase valuation adjustments	301	292	284
Net change in:
Other assets	(4,092)	(4,092)	(1,331)
Interest payable and other liabilities	(147)	(50)	(1,419)
Net cash provided by operating activities	18,858	24,911	13,913
Cash flows (to) from investing activities
Proceeds from sale of other real estate owned			267
Net cash (used in) provided by investing activities	(900)	(40,655)	(33,159)
Cash flows (to) from financing activities
Borrowings on bank stock loan	7,209	22,500	2,500
Principal repayments on bank stock loan	(13,669)	(9,550)	(1,000)
Proceeds from exercise of employee stock options	371	133	1,215
Principal payments on employee stock loan	44		121
Proceeds from employee stock purchase plan	405
Purchase of treasury stock	(10,867)
Net cash provided by (used in) financing activities	(16,507)	13,083	2,836
Net change in cash and cash equivalents	1,451	(2,661)	(16,410)
Cash and cash equivalents, beginning of period	1,540	4,201	20,611
Ending cash and cash equivalents	2,991	1,540	4,201
EBAC [Member] | Equity Bancshares, Inc. [Member]
Adjustments to reconcile net income to net cash from operating activities:
Equity in undistributed (income) loss	325	108
Cash flows (to) from investing activities
Net cash paid for acquisition	$ (900)	(3,370)
Prairie State Bancshares, Inc. [Member]
Cash flows (to) from investing activities
Net cash paid for acquisition			(6,744)
Prairie State Bancshares, Inc. [Member] | Equity Bancshares, Inc. [Member]
Cash flows (to) from investing activities
Net cash paid for acquisition			(12,510)
Eastman National Bancshares, Inc. [Member]
Cash flows (to) from investing activities
Net cash paid for acquisition		(55)	6,108
Eastman National Bancshares, Inc. [Member] | Equity Bancshares, Inc. [Member]
Cash flows (to) from investing activities
Net cash paid for acquisition		(55)	(7,813)
Cache Holdings, Inc. [Member]
Cash flows (to) from investing activities
Net cash paid for acquisition			(2,857)
Cache Holdings, Inc. [Member] | Equity Bancshares, Inc. [Member]
Cash flows (to) from investing activities
Net cash paid for acquisition			$ (13,103)
Kansas Bank Corporation [Member]
Cash flows (to) from investing activities
Net cash paid for acquisition		12,774
Kansas Bank Corporation [Member] | Equity Bancshares, Inc. [Member]
Cash flows (to) from investing activities
Net cash paid for acquisition		(14,151)
Adams Dairy Bancshares, Inc. [Member]
Cash flows (to) from investing activities
Net cash paid for acquisition		(1,385)
Adams Dairy Bancshares, Inc. [Member] | Equity Bancshares, Inc. [Member]
Cash flows (to) from investing activities
Net cash paid for acquisition		(4,179)
City Bank and Trust Company [Member]
Cash flows (to) from investing activities
Net cash paid for acquisition		8,759
City Bank and Trust Company [Member] | Equity Bancshares, Inc. [Member]
Cash flows (to) from investing activities
Net cash paid for acquisition		$ (18,900)