Schedule I - Condensed Financial Information of Registrant - Parent Company Only, Statements of Income and Comprehensive Income (Loss) (Detail) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenues:
Equity in income of subsidiaries									$ 73	$ 81	$ 41
Total	$ 3,287	$ 3,608	$ 3,590	$ 3,581	$ 3,555	$ 3,521	$ 3,359	$ 3,300	14,066	13,735	13,105
Expenses:
Interest									574	646	536
Total									13,232	12,153	12,169
Income before income tax									834	1,582	936
Income tax (expense) benefit									(128)	(170)	(220)
Net income									706	1,412	716
Total comprehensive income (loss)									(161)	1,361	788
Loews Corporation [Member]
Revenues:
Equity in income of subsidiaries									819	1,199	655
Interest and other									(11)	167	165
Total									808	1,366	820
Expenses:
Administrative									127	134	127
Interest									72	72	72
Total									199	206	199
Income before income tax									609	1,160	621
Income tax (expense) benefit									27	4	33
Net income									636	1,164	654
Equity in other comprehensive income (loss) of subsidiaries									(797)	197	134
Total comprehensive income (loss)									$ (161)	$ 1,361	$ 788