Mortgage Loans Serviced for Others, Amount

No definition available.

Name:	htlf_MortgageLoansServicedForOthersAmount
Namespace Prefix:	htlf_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Servicing Asset, Agreement Term

+ References

No definition available.

+ Details

Name:	htlf_ServicingAssetAgreementTerm
Namespace Prefix:	htlf_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Servicing Asset At Amortized Cost, Amortization, Term

+ References

No definition available.

+ Details

Name:	htlf_ServicingAssetAtAmortizedCostAmortizationTerm
Namespace Prefix:	htlf_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Valuation servicing rights in tranches [Line Items]

+ References

No definition available.

+ Details

Name:	htlf_ValuationServicingRightsInTranchesLineItems
Namespace Prefix:	htlf_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The designation of funds furnished by a borrower to a lender to assure future payments of the borrower's real estate taxes and insurance obligations with respect to a mortgaged property. Escrow deposits may be made for a variety of other purposes such as earnest money and contingent payments. This element excludes replacement reserves which are an escrow separately provided for within the US GAAP taxonomy.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.10)
-URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878

+ Details

Name:	us-gaap_EscrowDeposit
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Income from mortgage banking activities (fees and commissions) and servicing real estate mortgages, credit cards, and other financial assets held by others net of any related impairment of capitalized service costs. Also includes any premiums received in lieu of regular servicing fees on such loans only as earned over the life of the loans.

+ References

No definition available.

+ Details

Name:	us-gaap_FeesAndCommissionsMortgageBankingAndServicing
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Aggregate amount of servicing assets that are subsequently measured at fair value and servicing assets that are subsequently measured using the amortization method.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 50
-Section 45
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6469459&loc=d3e122501-111745

+ Details

Name:	us-gaap_ServicingAsset
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Fair value of contract to service financial assets under which the benefits of servicing are expected to more than adequately compensate the servicer.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 50
-Section 50
-Paragraph 4
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=116651436&loc=d3e122739-111746

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=7516967&loc=d3e66267-113978

+ Details

Name:	us-gaap_ServicingAssetAtAmortizedValueFairValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of increase (decrease) in the amortized amount from a decrease (increase) in the valuation allowance applied to the servicing asset for a contract to service financial assets under which the benefits of servicing are expected to more than adequately compensate the servicer.

+ References

+ Details

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

- Definition

Value of input used to measure servicing asset.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

+ Details

Name:	us-gaap_ServicingAssetMeasurementInput
Namespace Prefix:	us-gaap_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	instant

- Definition

Discount rate used to estimate the fair value of servicing assets and servicing liabilities.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 50
-Section 50
-Paragraph 2
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=116651436&loc=d3e122596-111746

+ Details

Name:	us-gaap_ServicingAssetsAndServicingLiabilitiesAtFairValueAssumptionsUsedToEstimateFairValueDiscountRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Estimated rate of prepayments of principal on servicing assets and servicing liabilities.

+ References

+ Details

Name:	us-gaap_ServicingAssetsAndServicingLiabilitiesAtFairValueAssumptionsUsedToEstimateFairValuePrepaymentSpeed
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis=htlf_MortgageServicingRightsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MeasurementInputTypeAxis=us-gaap_MeasurementInputCapRateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis=htlf_CommercialServicingRightsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis=htlf_MortgageServicingRights15YearTrancheMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis=htlf_MortgageServicingRights30YearTrancheMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis=htlf_CommercialServicingRightslessthan20YearsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis=htlf_CommercialServicingRightsmorethan20YearsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

GOODWILL, CORE DEPOSIT PREMIUM AND OTHER INTANGIBLE ASSETS (Mortgage and commercial loans servicing narrative) (Details)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2021 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2021 USD ($)	Jun. 30, 2020 USD ($)	Dec. 31, 2020 USD ($)
Valuation servicing rights in tranches [Line Items]
Mortgage loans serviced for others	$ 719,600,000		$ 719,600,000		$ 743,300,000
Custodial escrow balances maintained	13,100,000		13,100,000		5,700,000
Loans guaranteed and sold with servicing retained	6,201,000		6,201,000		6,052,000
Valuation allowance			1,900,000
Mortgage servicing rights
Valuation servicing rights in tranches [Line Items]
Fair value of mortgage servicing rights	5,600,000		$ 5,600,000		$ 5,200,000
Average constant prepayment rate			15.90%		16.20%
Servicing assets, discount rate			9.02%		9.02%
Fees collected for servicing of mortgage loans	$ 459,000	$ 410,000	$ 923,000	$ 819,000
Mortgage servicing rights \| Measurement Input, Cap Rate \| Minimum
Valuation servicing rights in tranches [Line Items]
Average capitalization rate (percent)	0.0079	0.0076	0.0079	0.0076
Mortgage servicing rights \| Measurement Input, Cap Rate \| Maximum
Valuation servicing rights in tranches [Line Items]
Average capitalization rate (percent)	0.0120	0.0116	0.0120	0.0116
Commercial servicing rights
Valuation servicing rights in tranches [Line Items]
Fair value of mortgage servicing rights	$ 1,104,000	$ 1,417,000	$ 1,104,000	$ 1,417,000	$ 1,300,000
Fees collected for servicing of mortgage loans	165,000	$ 54,000	294,000	$ 172,000
Loans guaranteed and sold with servicing retained	57,500,000		$ 57,500,000		$ 66,200,000
Commercial servicing rights \| Minimum
Valuation servicing rights in tranches [Line Items]
Average constant prepayment rate			13.70%		14.95%
Servicing assets, discount rate			5.70%		7.70%
Commercial servicing rights \| Maximum
Valuation servicing rights in tranches [Line Items]
Average constant prepayment rate			17.49%		19.25%
Servicing assets, discount rate			9.96%		12.88%
Commercial servicing rights \| Measurement Input, Cap Rate \| Minimum
Valuation servicing rights in tranches [Line Items]
Average capitalization rate (percent)					0.0310
Commercial servicing rights \| Measurement Input, Cap Rate \| Maximum
Valuation servicing rights in tranches [Line Items]
Average capitalization rate (percent)					0.0445
Mortgage Servicing Rights 15-year Tranche
Valuation servicing rights in tranches [Line Items]
Valuation allowance			$ 470,000		$ 422,000
Amortization period			15 years
Mortgage Servicing Rights 30-year Tranche
Valuation servicing rights in tranches [Line Items]
Valuation allowance					1,400,000
Amortization period			30 years
Less Than 20 Years
Valuation servicing rights in tranches [Line Items]
Fair value of mortgage servicing rights	170,000		$ 170,000		203,000
Period of tranche			20 years
Valuation allowance			$ 0		$ 0
Amortization period			20 years		20 years
More Than 20 Years
Valuation servicing rights in tranches [Line Items]
Fair value of mortgage servicing rights	$ 934,000		$ 934,000		$ 1,085,000
Period of tranche			20 years
Valuation allowance			$ 0		$ 0
Amortization period			20 years		20 years