Derivative Instruments (Effects Of Qualifying And Non-Qualifying Hedges) (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2022	Mar. 31, 2021
Realized Gain (Loss) [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total line items in which the effects of fair value or cash flow hedges are recorded	$ 266	$ 211
Net Investment Income [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total line items in which the effects of fair value or cash flow hedges are recorded	1,353	1,447
Benefits Expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total line items in which the effects of fair value or cash flow hedges are recorded	2,199	2,182
Interest Rate Contracts [Member] \| Realized Gain (Loss) [Member] \| Non-Qualifying Hedges [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Non-qualifying hedges gain (loss)	(821)	(1,159)
Equity Market Contracts [Member] \| Realized Gain (Loss) [Member] \| Non-Qualifying Hedges [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Non-qualifying hedges gain (loss)	(324)	1,242
LPR Ceded Derivative [Member] \| Benefits Expense [Member] \| Non-Qualifying Hedges [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Non-qualifying hedges gain (loss)	52	50
GLB Embedded Derivative [Member] \| Realized Gain (Loss) [Member] \| Non-Qualifying Hedges [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Non-qualifying hedges gain (loss)	1	3
Reinsurance Related [Member] \| Realized Gain (Loss) [Member] \| Non-Qualifying Hedges [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Non-qualifying hedges gain (loss)	546	342
Indexed Annuity And IUL Contracts [Member] \| Realized Gain (Loss) [Member] \| Non-Qualifying Hedges [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Non-qualifying hedges gain (loss)	506	(594)
Fair Value Hedges [Member] \| Interest Rate Contracts [Member] \| Net Investment Income [Member] \| Qualifying Hedges [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Hedged items	(63)	(84)
Derivatives designated as hedging instruments	63	84
Cash Flow Hedges [Member] \| Interest Rate Contracts [Member] \| Net Investment Income [Member] \| Qualifying Hedges [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain or (loss) reclassified from AOCI into income	1	1
Cash Flow Hedges [Member] \| Foreign Currency Contracts [Member] \| Realized Gain (Loss) [Member] \| Qualifying Hedges [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain or (loss) reclassified from AOCI into income	3	(2)
Cash Flow Hedges [Member] \| Foreign Currency Contracts [Member] \| Net Investment Income [Member] \| Qualifying Hedges [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain or (loss) reclassified from AOCI into income	$ 13	$ 10

Amount of income (expense) line items in statement of financial position that hedges are recorded

No definition available.

Name:	cik0000726865_AmountOfIncomeExpenseLineItemsInStatementOfFinancialPositionThatHedgesAreRecorded
Namespace Prefix:	cik0000726865_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of gain (loss) from the increase (decrease) in fair value of derivative and nonderivative instruments designated as fair value hedging instruments recognized in the income statement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 25
-Section 50
-Paragraph 1
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=121577467&loc=d3e76258-113986

+ Details

Name:	us-gaap_ChangeInUnrealizedGainLossOnFairValueHedgingInstruments1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of the increase (decrease) in fair value of the hedged item in a fair value hedge recognized in the income statement.

+ References

+ Details

Name:	us-gaap_ChangeInUnrealizedGainLossOnHedgedItemInFairValueHedge1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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_DerivativeInstrumentsGainLossLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The effective portion of net gain (loss) reclassified from accumulated other comprehensive income into income on derivative instruments designated and qualifying as hedging instruments.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4D
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=125515794&loc=SL5624177-113959

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=125515794&loc=SL5624171-113959

+ Details

Name:	us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of realized and unrealized gain (loss) of derivative instruments not designated or qualifying as hedging instruments.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4CC
-URI http://asc.fasb.org/extlink&oid=125515794&loc=SL109998890-113959

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=125515794&loc=SL5624171-113959

+ Details

Name:	us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	us-gaap_IncomeStatementLocationAxis=cik0000726865_RealizedGainLossMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_IncomeStatementLocationAxis=cik0000726865_NetInvestmentIncomeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_IncomeStatementLocationAxis=cik0000726865_BenefitsExpenseMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_InterestRateContractMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_HedgingDesignationAxis=us-gaap_NondesignatedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_EquityContractMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=cik0000726865_LprCededDerivativeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=cik0000726865_GuaranteedLivingBenefitsEmbeddedDerivativeReservesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=cik0000726865_ReinsuranceRelatedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=cik0000726865_IndexedAnnuityContractsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis=us-gaap_FairValueHedgingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_HedgingDesignationAxis=us-gaap_DesignatedAsHedgingInstrumentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis=us-gaap_CashFlowHedgingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_ForeignExchangeContractMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: