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Schedule of Compliance with Regulatory Capital Requirements Under Banking Regulations (Details) (Parenthetical)	3 Months Ended	12 Months Ended
	Mar. 31, 2021	Dec. 31, 2020
Banks Regulatory Capital Requirements [Member]
Entity Listings [Line Items]
Tier one capital conversation buffer	2.50%	2.50%

X

- Definition

The percentage of capital buffer to be maintained other than minimum capital requirements.

+ References

No definition available.

+ Details

Name:	LARK_TierOneCapitalConversationBuffer
Namespace Prefix:	LARK_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

X

- 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:	dei_EntityListingsLineItems
Namespace Prefix:	dei_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Details

Name:	dei_LegalEntityAxis=LARK_BanksRegulatoryCapitalRequirementsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: