Loans and Leases (Impaired loans not covered by loss share agreements) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
Mar. 31, 2015	Dec. 31, 2014
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Impaired loans with a related allowance, Unpaid Contractual Balance	$ 10,788	$ 16,664
Impaired loans without a related allowance, Unpaid Contractual Balance	60,233	53,132
Total impaired loans held to maturity, Unpaid Contractual Balance	71,021	69,796
Impaired Financing Receivable, Recorded Investment [Abstract]
Impaired loans with a related allowance, Loan Balance	10,097	16,462
Impaired loans without a related allowance, Loan Balance	49,444	45,262
Total impaired loans held to maturity, Loan Balance	59,541	61,724
Impaired loans, Related Allowance Recorded	1,934	2,697
Impaired Financing Receivable, Average Recorded Investment [Abstract]
Impaired loans with a related allowance, Avg. Loan Balance	12,384	22,942
Impaired loans without a related allowance, Avg. Loan Balance	39,906	39,466
Total impaired loans held to maturity, Avg. Loan Balance	52,290	62,408
Impaired Financing Receivable, Interest Income, Accrual Method [Abstract]
Impaired loans with a related allowance, Interest Income Recognized	59	457
Impaired loans without a related allowance, Interest Income Recognized	397	1,523
Total impaired loans held to maturity, Interest Income Recognized	456	1,980
Commercial
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Impaired loans with a related allowance, Unpaid Contractual Balance	307	780
Impaired loans without a related allowance, Unpaid Contractual Balance	4,022	4,913
Total impaired loans held to maturity, Unpaid Contractual Balance	4,329	5,693
Impaired Financing Receivable, Recorded Investment [Abstract]
Impaired loans with a related allowance, Loan Balance	273	780
Impaired loans without a related allowance, Loan Balance	3,293	3,746
Total impaired loans held to maturity, Loan Balance	3,566	4,526
Impaired loans, Related Allowance Recorded	205	754
Impaired Financing Receivable, Average Recorded Investment [Abstract]
Impaired loans with a related allowance, Avg. Loan Balance	520	5,594
Impaired loans without a related allowance, Avg. Loan Balance	3,584	3,499
Total impaired loans held to maturity, Avg. Loan Balance	4,104	9,093
Impaired Financing Receivable, Interest Income, Accrual Method [Abstract]
Impaired loans with a related allowance, Interest Income Recognized	3	19
Impaired loans without a related allowance, Interest Income Recognized	33	101
Total impaired loans held to maturity, Interest Income Recognized	36	120
Commercial real estate
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Impaired loans with a related allowance, Unpaid Contractual Balance	1,973	7,356
Impaired loans without a related allowance, Unpaid Contractual Balance	42,421	32,708
Total impaired loans held to maturity, Unpaid Contractual Balance	44,394	40,064
Impaired Financing Receivable, Recorded Investment [Abstract]
Impaired loans with a related allowance, Loan Balance	1,484	7,322
Impaired loans without a related allowance, Loan Balance	34,388	28,449
Total impaired loans held to maturity, Loan Balance	35,872	35,771
Impaired loans, Related Allowance Recorded	466	636
Impaired Financing Receivable, Average Recorded Investment [Abstract]
Impaired loans with a related allowance, Avg. Loan Balance	3,279	5,931
Impaired loans without a related allowance, Avg. Loan Balance	23,997	24,522
Total impaired loans held to maturity, Avg. Loan Balance	27,276	30,453
Impaired Financing Receivable, Interest Income, Accrual Method [Abstract]
Impaired loans with a related allowance, Interest Income Recognized	6	303
Impaired loans without a related allowance, Interest Income Recognized	292	1,172
Total impaired loans held to maturity, Interest Income Recognized	298	1,475
Commercial and commercial real estate
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Impaired loans with a related allowance, Unpaid Contractual Balance	2,280	8,136
Impaired loans without a related allowance, Unpaid Contractual Balance	46,443	37,621
Total impaired loans held to maturity, Unpaid Contractual Balance	48,723	45,757
Impaired Financing Receivable, Recorded Investment [Abstract]
Impaired loans with a related allowance, Loan Balance	1,757	8,102
Impaired loans without a related allowance, Loan Balance	37,681	32,195
Total impaired loans held to maturity, Loan Balance	39,438	40,297
Impaired loans, Related Allowance Recorded	671	1,390
Impaired Financing Receivable, Average Recorded Investment [Abstract]
Impaired loans with a related allowance, Avg. Loan Balance	3,799	11,525
Impaired loans without a related allowance, Avg. Loan Balance	27,581	28,021
Total impaired loans held to maturity, Avg. Loan Balance	31,380	39,546
Impaired Financing Receivable, Interest Income, Accrual Method [Abstract]
Impaired loans with a related allowance, Interest Income Recognized	9	322
Impaired loans without a related allowance, Interest Income Recognized	325	1,273
Total impaired loans held to maturity, Interest Income Recognized	334	1,595
Agricultural and agricultural real estate
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Impaired loans with a related allowance, Unpaid Contractual Balance	3,276	3,317
Impaired loans without a related allowance, Unpaid Contractual Balance	3,692	3,961
Total impaired loans held to maturity, Unpaid Contractual Balance	6,968	7,278
Impaired Financing Receivable, Recorded Investment [Abstract]
Impaired loans with a related allowance, Loan Balance	3,276	3,317
Impaired loans without a related allowance, Loan Balance	1,713	1,732
Total impaired loans held to maturity, Loan Balance	4,989	5,049
Impaired loans, Related Allowance Recorded	49	52
Impaired Financing Receivable, Average Recorded Investment [Abstract]
Impaired loans with a related allowance, Avg. Loan Balance	3,291	3,966
Impaired loans without a related allowance, Avg. Loan Balance	1,588	3,308
Total impaired loans held to maturity, Avg. Loan Balance	4,879	7,274
Impaired Financing Receivable, Interest Income, Accrual Method [Abstract]
Impaired loans with a related allowance, Interest Income Recognized	41	104
Impaired loans without a related allowance, Interest Income Recognized	3	13
Total impaired loans held to maturity, Interest Income Recognized	44	117
Residential real estate
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Impaired loans with a related allowance, Unpaid Contractual Balance	2,749	2,412
Impaired loans without a related allowance, Unpaid Contractual Balance	7,861	8,200
Total impaired loans held to maturity, Unpaid Contractual Balance	10,610	10,612
Impaired Financing Receivable, Recorded Investment [Abstract]
Impaired loans with a related allowance, Loan Balance	2,581	2,244
Impaired loans without a related allowance, Loan Balance	7,820	7,991
Total impaired loans held to maturity, Loan Balance	10,401	10,235
Impaired loans, Related Allowance Recorded	491	442
Impaired Financing Receivable, Average Recorded Investment [Abstract]
Impaired loans with a related allowance, Avg. Loan Balance	2,674	3,398
Impaired loans without a related allowance, Avg. Loan Balance	7,726	6,267
Total impaired loans held to maturity, Avg. Loan Balance	10,400	9,665
Impaired Financing Receivable, Interest Income, Accrual Method [Abstract]
Impaired loans with a related allowance, Interest Income Recognized	4	12
Impaired loans without a related allowance, Interest Income Recognized	58	110
Total impaired loans held to maturity, Interest Income Recognized	62	122
Consumer
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Impaired loans with a related allowance, Unpaid Contractual Balance	2,483	2,799
Impaired loans without a related allowance, Unpaid Contractual Balance	2,237	3,350
Total impaired loans held to maturity, Unpaid Contractual Balance	4,720	6,149
Impaired Financing Receivable, Recorded Investment [Abstract]
Impaired loans with a related allowance, Loan Balance	2,483	2,799
Impaired loans without a related allowance, Loan Balance	2,230	3,344
Total impaired loans held to maturity, Loan Balance	4,713	6,143
Impaired loans, Related Allowance Recorded	723	813
Impaired Financing Receivable, Average Recorded Investment [Abstract]
Impaired loans with a related allowance, Avg. Loan Balance	2,620	4,053
Impaired loans without a related allowance, Avg. Loan Balance	3,011	1,870
Total impaired loans held to maturity, Avg. Loan Balance	5,631	5,923
Impaired Financing Receivable, Interest Income, Accrual Method [Abstract]
Impaired loans with a related allowance, Interest Income Recognized	5	19
Impaired loans without a related allowance, Interest Income Recognized	11	127
Total impaired loans held to maturity, Interest Income Recognized	$ 16	$ 146

Average amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 15

-Subparagraph (c)(1)

-URI http://asc.fasb.org/extlink&oid=35738203&loc=d3e5212-111524

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 17

-URI http://asc.fasb.org/extlink&oid=35738203&loc=d3e5258-111524

+ Details

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

- Details

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

- Definition

Amount of interest income recognized that the financing receivables (with related allowance for credit losses and without a related allowance for credit losses) were impaired.

+ References

+ Details

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

- Details

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

- Definition

Amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 14A

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=35738203&loc=SL6953550-111524

+ Details

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

- Details

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

- Definition

Amount of allowance for credit losses related to recorded investment.

+ References

+ Details

Name:	us-gaap_ImpairedFinancingReceivableRelatedAllowance
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of unpaid principal balance of impaired financing receivables with related allowance for credit losses and without related allowance for credit losses.

+ References

+ Details

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

- Details

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

- Definition

Amount of average investment of impaired financing receivables for which there is no related allowance for credit losses.

+ References

+ Details

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

- Definition

Amount of interest income, recognized on accrual basis, on financing receivables that are recognized as impaired, for which there is no related allowance for credit losses.

+ References

+ Details

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

- Definition

Amount of investment in impaired financing receivables for which there is no related allowance for credit losses.

+ References

+ Details

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

- Definition

Amount of unpaid principal balance of impaired financing receivables for which there is no related allowance for credit losses.

+ References

+ Details

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

- Definition

Amount of average investment of impaired financing receivables for which there is a related allowance for credit losses.

+ References

+ Details

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

- Definition

Amount of interest income, recognized on accrual basis, on financing receivables, for which there is a related allowance for credit losses and are recognized as impaired.

+ References

+ Details

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

- Definition

Amount of investment in impaired financing receivables for which there is a related allowance for credit losses.

+ References

+ Details

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

- Definition

Unpaid principal balance of impaired financing receivables for which there is a related allowance for credit losses.

+ References

+ Details

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

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=htlf_AgriculturalPortfolioSegmentMember
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=us-gaap_CommercialPortfolioSegmentMember
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_ConsumerPortfolioSegmentMember
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: