Reinsurance Contract, Ceded Commission Percentage

No definition available.

Name:	lmnd_ReinsuranceContractCededCommissionPercentage
Namespace Prefix:	lmnd_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Reinsurance Contract, Claims Funding Percentage

+ References

No definition available.

+ Details

Name:	lmnd_ReinsuranceContractClaimsFundingPercentage
Namespace Prefix:	lmnd_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Reinsurance Program, Minimum Losses Threshold

+ References

No definition available.

+ Details

Name:	lmnd_ReinsuranceProgramMinimumLossesThreshold
Namespace Prefix:	lmnd_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Ratio of insurance contracts that are subject to reinsurance participation to all contracts in force.

+ References

No definition available.

+ Details

Name:	us-gaap_ContractsInForceSubjectToParticipationThroughReinsurancePercentage
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

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

- Definition

Amount, after effects of reinsurance, of expense for claims incurred in the current reporting period and related claims settlement costs.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 50
-Paragraph 3
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=116884095&loc=d3e14764-158437

+ Details

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

- Definition

Amount, after effects of reinsurance, of expense (reversal of expense) for claims incurred in prior reporting periods and related claims settlement costs.

+ References

+ Details

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

- Details

Name:	us-gaap_UnusualOrInfrequentItemAxis=lmnd_WinterStormUriMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ReinsurancePolicyTypeAxis=lmnd_ProportionalReinsuranceContractsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ReinsurancePolicyTypeAxis=lmnd_NonProportionalReinsuranceContractsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Unpaid Loss and Loss Adjustment Expense - Additional Information (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
	Jul. 01, 2021	Mar. 31, 2022	Mar. 31, 2021	Jun. 30, 2021
Effects of Reinsurance [Line Items]
Favorable (unfavorable) development on net loss and LAE reserves		$ (0.4)	$ (0.2)
Current accident year incurred loss and LAE		24.8	16.7
Reinsurance program, minimum losses threshold		$ 60.0
Winter Storm Uri
Effects of Reinsurance [Line Items]
Current accident year incurred loss and LAE			$ 6.5
Proportional Reinsurance Contracts
Effects of Reinsurance [Line Items]
Percent of contracts subject to participation through reinsurance	70.00%			75.00%
Ceded commission percentage		25.00%
Claims funding percentage		75.00%
Non-Proportional Reinsurance Contracts
Effects of Reinsurance [Line Items]
Percent of contracts subject to participation through reinsurance		25.00%