LOANS (Troubled Debt Restructurings on Financing Receivables) (Details) $ in Thousands	12 Months Ended
Dec. 31, 2022 USD ($) loan	Dec. 31, 2021 USD ($) loan
Financing Receivable, Modifications [Line Items]
Number of Loans \| loan	2	2
Pre-Modification Recorded Investment	$ 6,458	$ 7,580
Post-Modification Recorded Investment	$ 6,458	$ 7,580
Commercial and industrial \| Commercial and industrial
Financing Receivable, Modifications [Line Items]
Number of Loans \| loan	0	0
Pre-Modification Recorded Investment	$ 0	$ 0
Post-Modification Recorded Investment	$ 0	$ 0
Commercial and industrial \| Paycheck Protection Program ("PPP")
Financing Receivable, Modifications [Line Items]
Number of Loans \| loan	0	0
Pre-Modification Recorded Investment	$ 0	$ 0
Post-Modification Recorded Investment	$ 0	$ 0
Commercial and industrial \| Owner occupied commercial real estate
Financing Receivable, Modifications [Line Items]
Number of Loans \| loan	1	0
Pre-Modification Recorded Investment	$ 5,058	$ 0
Post-Modification Recorded Investment	$ 5,058	$ 0
Commercial and industrial \| Non-owner occupied commercial real estate
Financing Receivable, Modifications [Line Items]
Number of Loans \| loan	0	2
Pre-Modification Recorded Investment	$ 0	$ 7,580
Post-Modification Recorded Investment	$ 0	$ 7,580
Commercial and industrial \| Real estate construction
Financing Receivable, Modifications [Line Items]
Number of Loans \| loan	0	0
Pre-Modification Recorded Investment	$ 0	$ 0
Post-Modification Recorded Investment	$ 0	$ 0
Agricultural and agricultural real estate
Financing Receivable, Modifications [Line Items]
Number of Loans \| loan	1	0
Pre-Modification Recorded Investment	$ 1,400	$ 0
Post-Modification Recorded Investment	$ 1,400	$ 0
Residential real estate
Financing Receivable, Modifications [Line Items]
Number of Loans \| loan	0	0
Pre-Modification Recorded Investment	$ 0	$ 0
Post-Modification Recorded Investment	$ 0	$ 0
Consumer
Financing Receivable, Modifications [Line Items]
Number of Loans \| loan	0	0
Pre-Modification Recorded Investment	$ 0	$ 0
Post-Modification Recorded Investment	$ 0	$ 0

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.

No definition available.

+ Details

Name:	us-gaap_FinancingReceivableModificationsLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of financing receivables that have been modified by troubled debt restructurings.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 33
-URI https://asc.fasb.org/extlink&oid=123577603&loc=SL6953676-111524

+ Details

Name:	us-gaap_FinancingReceivableModificationsNumberOfContracts2
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount, after troubled debt restructuring, of modified financing receivable.

+ References

+ Details

Name:	us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount, before troubled debt restructuring, of financing receivable to be modified.

+ References

+ Details

Name:	us-gaap_FinancingReceivableModificationsPreModificationRecordedInvestment2
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_CommercialPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_CommercialLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=htlf_PaycheckProtectionProgramLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=htlf_OwnerOccupiedCommercialRealEstateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=htlf_NonOwnerOccupiedCommercialRealEstateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_RealEstateLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=htlf_AgriculturalPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_ResidentialPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_ConsumerPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: