Long-Term Debt - Junior Subordinated Notes (Details) - Junior subordinated notes - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Debt instrument, face amount	$ 44,847	$ 44,847
Debt instrument, book value	41,631	41,587
ATBancorp Statutory Trust I
Debt Instrument [Line Items]
Debt instrument, face amount	7,732	7,732
Debt instrument, book value	$ 6,823	$ 6,814
Interest rate	2.42%	3.57%
ATBancorp Statutory Trust I \| LIBOR
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate	1.68%
ATBancorp Statutory Trust II
Debt Instrument [Line Items]
Debt instrument, face amount	$ 12,372	$ 12,372
Debt instrument, book value	$ 10,808	$ 10,794
Interest rate	2.39%	3.54%
ATBancorp Statutory Trust II \| LIBOR
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate	1.65%
Central Bancshares Capital Trust II
Debt Instrument [Line Items]
Debt instrument, face amount	$ 7,217	$ 7,217
Debt instrument, book value	$ 6,795	$ 6,783
Interest rate	4.24%	5.39%
Central Bancshares Capital Trust II \| LIBOR
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate	3.50%
Barron Investment Capital Trust I
Debt Instrument [Line Items]
Debt instrument, face amount	$ 2,062	$ 2,062
Debt instrument, book value	$ 1,741	$ 1,732
Interest rate	3.35%	4.08%
Barron Investment Capital Trust I \| LIBOR
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate	2.15%
MidWestOne Statutory Trust II
Debt Instrument [Line Items]
Debt instrument, face amount	$ 15,464	$ 15,464
Debt instrument, book value	$ 15,464	$ 15,464
Interest rate	2.33%	3.48%
MidWestOne Statutory Trust II \| LIBOR
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate	1.59%

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

No definition available.

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- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
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-Section 55
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-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

+ Details

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- Definition

Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 6
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109500613&loc=SL6036836-161870

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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
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-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

Including the current and noncurrent portions, the carrying value of junior subordinated long-term debt owed to unconsolidated subsidiary trusts as of the balance sheet date. Such debt places a lender in a lien position behind debt having a higher priority of repayment in liquidation of the entity's assets and was initially scheduled to be repaid after one year or beyond the normal operating cycle if longer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.16)
-URI http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910

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-Publisher FASB
-Name Accounting Standards Codification
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-Section S99
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-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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