Summary of Significant Accounting Policies, Future Policy Benefit Reserves (Details) - USD ($) $ in Millions	Dec. 31, 2020	Sep. 30, 2020	Dec. 31, 2019
Future Policy Benefit Reserves [Abstract]
Premium deficiency		$ 74
Long term care active life reserves, weighted average interest rate	5.40%		5.70%

The interest-adjusted benefit ratio, which includes the change in active life reserves and investment income.

No definition available.

Name:	l_LongTermCareActiveLifeReservesInterestRate
Namespace Prefix:	l_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant