Summary of Significant Accounting Policies, Investments (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019
Investments [Abstract]
Increase in shadow adjustments	$ 515	$ 1,000
Shadow adjustments	$ 2,500	$ 2,000

To the extent that unrealized gains on fixed income securities supporting long term care products and structured settlements not funded by annuities would result in a premium deficiency if those gains were realized, a related increase in Insurance reserves is recorded, net of tax and noncontrolling interests, as a reduction of net unrealized gains through Other comprehensive income (loss) (Shadow Adjustments).

No definition available.

Name:	l_ShadowAdjustments
Namespace Prefix:	l_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant