Loans and Leases (Troubled debt restructuring with payment default) (Details) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2015 USD ($) loan	Sep. 30, 2014 USD ($) loan	Sep. 30, 2015 USD ($) loan	Sep. 30, 2014 USD ($) loan
Financing Receivable, Modifications [Line Items]
Number of Loans	1	1	1	1
Recorded Investment \| $	$ 814	$ 60	$ 814	$ 60
Commercial
Financing Receivable, Modifications [Line Items]
Number of Loans	0	0	0	0
Recorded Investment \| $	$ 0	$ 0	$ 0	$ 0
Commercial real estate
Financing Receivable, Modifications [Line Items]
Number of Loans	1	0	1	0
Recorded Investment \| $	$ 814	$ 0	$ 814	$ 0
Commercial and commercial real estate
Financing Receivable, Modifications [Line Items]
Number of Loans	1	0	1	0
Recorded Investment \| $	$ 814	$ 0	$ 814	$ 0
Agricultural and agricultural real estate
Financing Receivable, Modifications [Line Items]
Number of Loans	0	1	0	1
Recorded Investment \| $	$ 0	$ 60	$ 0	$ 60
Residential real estate
Financing Receivable, Modifications [Line Items]
Number of Loans	0	0	0	0
Recorded Investment \| $	$ 0	$ 0	$ 0	$ 0
Consumer
Financing Receivable, Modifications [Line Items]
Number of Loans	0	0	0	0
Recorded Investment \| $	$ 0	$ 0	$ 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 within the previous 12 months and for which there was a payment default.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 34

-URI http://asc.fasb.org/extlink&oid=49124121&loc=SL6953682-111524

+ Details

Name:	us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of investment related to financing receivables modified by troubled debt restructurings within the previous 12 months, for which there was a payment default.

+ References

+ Details

Name:	us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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