XML 173 R145.htm IDEA: XBRL DOCUMENT
v3.20.4

Investments - Additional Information (Details) - security | Sep. 30, 2020 | Dec. 31, 2019 | Dec. 31, 2018
--- | --- | --- | ---
Investments |  |  |
Number of debt securities held | 7 | 9 | 7
Number of debt securities held, unrealized loss position for 12 months or more | 0 | 4 | 6

X
- Definition Debt Securities, Available For Sale, Number Of Positions + References No definition available. + Details
Name: | lmda_DebtSecuritiesAvailableForSaleNumberOfPositions
Namespace Prefix: | lmda_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Number of investments in debt securities measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for 12 months or longer, without an allowance for credit loss. Includes beneficial interest in securitized financial asset. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 50 -Paragraph 4 -Subparagraph (b)(3) -URI http://asc.fasb.org/extlink&oid=121582814&loc=SL82922888-210455 + Details
Name: | us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerNumberOfPositions
Namespace Prefix: | us-gaap_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- References No definition available. + Details
Name: | us-gaap_InvestmentsDebtAndEquitySecuritiesAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration