Loans, Leases and Other Real Estate - Impaired Loans with and without Specific Allowances (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2018	Dec. 31, 2017
Financing Receivable, Impaired [Line Items]
Recorded Investment in Impaired Loans	$ 19,560	$ 22,591
Contractual Unpaid Principal Balance	21,273	23,461
Related Allowance	423	505
Average Investment in Impaired Loans	21,854	23,236
Interest Income Recognized	177	705
Commercial, secured by real estate
Financing Receivable, Impaired [Line Items]
Loans without related allowance, Recorded Investment in Impaired Loans	6,342	12,155
Loans with related allowance, Recorded Investment in Impaired Loans	7,424	5,381
Recorded Investment in Impaired Loans	13,766	17,536
Loans without related allowance, Contractual Unpaid Principal Balance	6,535	12,497
Loans with related allowance, Contractual Unpaid Principal Balance	7,767	5,721
Contractual Unpaid Principal Balance	14,302	18,218
Related Allowance	386	454
Loans without related allowance, Average Investment in Impaired Loans	7,799	12,774
Loans with related allowance, Average Investment in Impaired Loans	9,035	5,029
Average Investment in Impaired Loans	16,834	17,803
Loans without related allowance, Interest Income Recognized	53	366
Loans with related allowance, Interest Income Recognized	98	206
Interest Income Recognized	151	572
Commercial, industrial and other
Financing Receivable, Impaired [Line Items]
Loans without related allowance, Recorded Investment in Impaired Loans	1,871	618
Loans with related allowance, Recorded Investment in Impaired Loans	236	164
Recorded Investment in Impaired Loans	2,107	782
Loans without related allowance, Contractual Unpaid Principal Balance	2,869	618
Loans with related allowance, Contractual Unpaid Principal Balance	235	164
Contractual Unpaid Principal Balance	3,104	782
Related Allowance	9	9
Loans without related allowance, Average Investment in Impaired Loans	584	618
Loans with related allowance, Average Investment in Impaired Loans	235	283
Average Investment in Impaired Loans	819	901
Loans without related allowance, Interest Income Recognized	5	25
Loans with related allowance, Interest Income Recognized	3	14
Interest Income Recognized	8	39
Leases
Financing Receivable, Impaired [Line Items]
Loans without related allowance, Recorded Investment in Impaired Loans	0	0
Loans with related allowance, Recorded Investment in Impaired Loans	36	65
Recorded Investment in Impaired Loans	36	65
Loans without related allowance, Contractual Unpaid Principal Balance	0	0
Loans with related allowance, Contractual Unpaid Principal Balance	36	65
Contractual Unpaid Principal Balance	36	65
Related Allowance	16	30
Loans without related allowance, Average Investment in Impaired Loans	0	0
Loans with related allowance, Average Investment in Impaired Loans	36	29
Average Investment in Impaired Loans	36	29
Loans without related allowance, Interest Income Recognized	0	0
Loans with related allowance, Interest Income Recognized	0	0
Interest Income Recognized	0	0
Real estate - residential mortgage
Financing Receivable, Impaired [Line Items]
Loans without related allowance, Recorded Investment in Impaired Loans	429	963
Loans with related allowance, Recorded Investment in Impaired Loans	771	781
Recorded Investment in Impaired Loans	1,200	1,744
Loans without related allowance, Contractual Unpaid Principal Balance	444	980
Loans with related allowance, Contractual Unpaid Principal Balance	911	919
Contractual Unpaid Principal Balance	1,355	1,899
Related Allowance	4	4
Loans without related allowance, Average Investment in Impaired Loans	947	996
Loans with related allowance, Average Investment in Impaired Loans	772	940
Average Investment in Impaired Loans	1,719	1,936
Loans without related allowance, Interest Income Recognized	4	15
Loans with related allowance, Interest Income Recognized	5	27
Interest Income Recognized	9	42
Real estate - construction
Financing Receivable, Impaired [Line Items]
Loans without related allowance, Recorded Investment in Impaired Loans	1,471	1,471
Loans with related allowance, Recorded Investment in Impaired Loans	0	0
Recorded Investment in Impaired Loans	1,471	1,471
Loans without related allowance, Contractual Unpaid Principal Balance	1,471	1,471
Loans with related allowance, Contractual Unpaid Principal Balance	0	0
Contractual Unpaid Principal Balance	1,471	1,471
Related Allowance	0	0
Loans without related allowance, Average Investment in Impaired Loans	1,471	1,471
Loans with related allowance, Average Investment in Impaired Loans	0	0
Average Investment in Impaired Loans	1,471	1,471
Loans without related allowance, Interest Income Recognized	0	0
Loans with related allowance, Interest Income Recognized	0	0
Interest Income Recognized	0	0
Home equity and consumer
Financing Receivable, Impaired [Line Items]
Loans without related allowance, Recorded Investment in Impaired Loans	0	0
Loans with related allowance, Recorded Investment in Impaired Loans	980	993
Recorded Investment in Impaired Loans	980	993
Loans without related allowance, Contractual Unpaid Principal Balance	0	0
Loans with related allowance, Contractual Unpaid Principal Balance	1,005	1,026
Contractual Unpaid Principal Balance	1,005	1,026
Related Allowance	8	8
Loans without related allowance, Average Investment in Impaired Loans	0	6
Loans with related allowance, Average Investment in Impaired Loans	975	1,090
Average Investment in Impaired Loans	975	1,096
Loans without related allowance, Interest Income Recognized	0	0
Loans with related allowance, Interest Income Recognized	9	52
Interest Income Recognized	$ 9	$ 52

Amount of valuation allowance for financing receivables that are expected to be uncollectible that were individually evaluated for impairment.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953423-111524

+ Details

Name:	us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- 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.

+ Details

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

- Definition

Average 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 15
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=84173941&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=84173941&loc=d3e5258-111524

+ Details

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

- Definition

Amount of interest income recognized on a cash-basis method of accounting 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_ImpairedFinancingReceivableInterestIncomeCashBasisMethod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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=84173941&loc=SL6953550-111524

+ Details

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

- Definition

Amount of average investment of impaired financing receivables for which there is no 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 17
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5258-111524

Reference 2: 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=84173941&loc=d3e5212-111524

+ 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 cash basis, on financing receivables, for which there is no related allowance for credit losses and are recognized as impaired.

+ References

+ Details

Name:	us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeCashBasisMethod
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 on financing receivables, for which there is a related allowance for credit losses, recognized on a cash-basis method of accounting that the financing receivables were impaired.

+ References

+ Details

Name:	us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeCashBasisMethod
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_FinancingReceivablePortfolioSegmentAxis=us-gaap_CommercialRealEstatePortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

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

- Details

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