Loans and Other Real Estate - Impaired Loans with and without Specific Allowances (Detail) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Financing Receivable, Impaired [Line Items]
Recorded Investment in Impaired Loans	$ 22,124	$ 19,702	$ 22,591
Contractual Unpaid Principal Balance	22,776	21,360	23,461
Loans with related allowance, Related Allowance	352	338
Related Allowance	352	338	505
Interest Income Recognized	426	592	705
Average Investment in Impaired Loans	18,342	20,012	23,236
Commercial, secured by real estate
Financing Receivable, Impaired [Line Items]
Loans without related allowance, Recorded Investment in Impaired Loans	12,478	9,284	12,155
Loans with related allowance, Recorded Investment in Impaired Loans	3,470	7,270	5,381
Recorded Investment in Impaired Loans	15,948	16,554	17,536
Loans without related allowance, Contractual Unpaid Principal Balance	12,630	9,829	12,497
Loans with related allowance, Contractual Unpaid Principal Balance	3,706	7,597	5,721
Contractual Unpaid Principal Balance	16,336	17,426	18,218
Loans with related allowance, Related Allowance	228	307	454
Related Allowance	228	307	454
Loans without related allowance, Interest Income Recognized	164	188	366
Loans with related allowance, Interest Income Recognized	190	317	206
Interest Income Recognized	354	505	572
Loans without related allowance, Average Investment in Impaired Loans	10,386	7,369	12,774
Loans with related allowance, Average Investment in Impaired Loans	4,554	7,594	5,029
Average Investment in Impaired Loans	14,940	14,963	17,803
Commercial, industrial and other
Financing Receivable, Impaired [Line Items]
Loans without related allowance, Recorded Investment in Impaired Loans	1,391	1,151	618
Loans with related allowance, Recorded Investment in Impaired Loans	113	209	164
Recorded Investment in Impaired Loans	1,504	1,360	782
Loans without related allowance, Contractual Unpaid Principal Balance	1,381	1,449	618
Loans with related allowance, Contractual Unpaid Principal Balance	113	209	164
Contractual Unpaid Principal Balance	1,494	1,658	782
Loans with related allowance, Related Allowance	5	7	9
Related Allowance	5	7	9
Loans without related allowance, Interest Income Recognized	16	19	25
Loans with related allowance, Interest Income Recognized	6	12	14
Interest Income Recognized	22	31	39
Loans without related allowance, Average Investment in Impaired Loans	1,334	1,834	618
Loans with related allowance, Average Investment in Impaired Loans	113	209	283
Average Investment in Impaired Loans	1,447	2,043	901
Equipment finance
Financing Receivable, Impaired [Line Items]
Loans without related allowance, Recorded Investment in Impaired Loans	0	301	0
Loans with related allowance, Recorded Investment in Impaired Loans	23	30	65
Recorded Investment in Impaired Loans	23	331	65
Loans without related allowance, Contractual Unpaid Principal Balance	0	597	0
Loans with related allowance, Contractual Unpaid Principal Balance	23	30	65
Contractual Unpaid Principal Balance	23	627	65
Loans with related allowance, Related Allowance	10	14	30
Related Allowance	10	14	30
Loans without related allowance, Interest Income Recognized	0	0	0
Loans with related allowance, Interest Income Recognized	0	0	0
Interest Income Recognized	0	0	0
Loans without related allowance, Average Investment in Impaired Loans	0	376	0
Loans with related allowance, Average Investment in Impaired Loans	21	19	29
Average Investment in Impaired Loans	21	395	29
Real estate - residential mortgage
Financing Receivable, Impaired [Line Items]
Loans without related allowance, Recorded Investment in Impaired Loans	803	0	963
Loans with related allowance, Recorded Investment in Impaired Loans	1,512	730	781
Recorded Investment in Impaired Loans	2,315	730	1,744
Loans without related allowance, Contractual Unpaid Principal Balance	815	0	980
Loans with related allowance, Contractual Unpaid Principal Balance	1,682	884	919
Contractual Unpaid Principal Balance	2,497	884	1,899
Loans with related allowance, Related Allowance	104	4	4
Related Allowance	104	4	4
Loans without related allowance, Interest Income Recognized	0	4	15
Loans with related allowance, Interest Income Recognized	19	20	27
Interest Income Recognized	19	24	42
Loans without related allowance, Average Investment in Impaired Loans	233	242	996
Loans with related allowance, Average Investment in Impaired Loans	926	745	940
Average Investment in Impaired Loans	1,159	987	1,936
Real estate - construction
Financing Receivable, Impaired [Line Items]
Loans without related allowance, Recorded Investment in Impaired Loans	1,663	0	1,471
Loans with related allowance, Recorded Investment in Impaired Loans	0	0	0
Recorded Investment in Impaired Loans	1,663	0	1,471
Loans without related allowance, Contractual Unpaid Principal Balance	1,661	0	1,471
Loans with related allowance, Contractual Unpaid Principal Balance	0	0	0
Contractual Unpaid Principal Balance	1,661	0	1,471
Loans with related allowance, Related Allowance	0	0	0
Related Allowance	0	0	0
Loans without related allowance, Interest Income Recognized	2	0	0
Loans with related allowance, Interest Income Recognized	0	0	0
Interest Income Recognized	2	0	0
Loans without related allowance, Average Investment in Impaired Loans	82	726	1,471
Loans with related allowance, Average Investment in Impaired Loans	0	0	0
Average Investment in Impaired Loans	82	726	1,471
Home equity and consumer
Financing Receivable, Impaired [Line Items]
Loans without related allowance, Recorded Investment in Impaired Loans	0	0	0
Loans with related allowance, Recorded Investment in Impaired Loans	671	727	993
Recorded Investment in Impaired Loans	671	727	993
Loans without related allowance, Contractual Unpaid Principal Balance	0	0	0
Loans with related allowance, Contractual Unpaid Principal Balance	765	765	1,026
Contractual Unpaid Principal Balance	765	765	1,026
Loans with related allowance, Related Allowance	5	6	8
Related Allowance	5	6	8
Loans without related allowance, Interest Income Recognized	0	0	0
Loans with related allowance, Interest Income Recognized	29	32	52
Interest Income Recognized	29	32	52
Loans without related allowance, Average Investment in Impaired Loans	0	0	6
Loans with related allowance, Average Investment in Impaired Loans	693	898	1,090
Average Investment in Impaired Loans	$ 693	$ 898	$ 1,096

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

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-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://fasb.org/us-gaap/role/ref/legacyRef
-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://fasb.org/us-gaap/role/ref/legacyRef
-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://fasb.org/us-gaap/role/ref/legacyRef
-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 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

- Definition

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

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-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://fasb.org/us-gaap/role/ref/legacyRef
-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: