Short-Term and Long-Term Debt - Credit Facilities and Letters of Credit (Details) $ in Millions	Dec. 31, 2023 USD ($)
Line of Credit Facility [Line Items]
Maximum Available	$ 3,835
LOCs Issued	1,892
Five-year revolving credit facility
Line of Credit Facility [Line Items]
Maximum Available	2,000
LOCs Issued	116
LOC facility due August 2031
Line of Credit Facility [Line Items]
Maximum Available	976
LOCs Issued	917
LOC facility due October 2031
Line of Credit Facility [Line Items]
Maximum Available	859
LOCs Issued	$ 859

Amount of letters of credit issued under credit facilities as of the balance-sheet date.

No definition available.

Name:	cik0000726865_LettersOfCreditIssued
Namespace Prefix:	cik0000726865_
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

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(f))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480678/235-10-S99-1

+ Details

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

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480566/210-10-S99-1

+ Details

Name:	us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	us-gaap_LineOfCreditFacilityAxis=cik0000726865_FiveYearRevolvingCreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LineOfCreditFacilityAxis=cik0000726865_LineOfCreditFacilityDueAugust2031Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LineOfCreditFacilityAxis=cik0000726865_LineOfCreditFacilityDueOctober2031Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: