Guaranteed Benefit Features (Narrative) (Details)	3 Months Ended	9 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Guaranteed Benefit Features [Abstract]
Percent of permanent life insurance in force	35.00%		35.00%		33.00%
Percent of permanent life insurance sales	25.00%	38.00%	28.00%	34.00%

Universal life and variable universal life products with secondary guarantees in force as a percentage of total permanent life insurance in force.

No definition available.

Name:	cik0000726865_PercentOfPermanentLifeInsuranceInForce
Namespace Prefix:	cik0000726865_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant