Schedule I - Condensed Financial Information of Registrant - Parent Company Only, Statements of Cash Flows (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operating Activities:
Net income	$ 706	$ 1,412	$ 716
Adjustments to reconcile net income to net cash provided (used) by operating activities:
Equity method investees	572	25	221
Provision for deferred income taxes	86	(47)	102
Changes in operating assets and liabilities, net:
Receivables	(131)	93	24
Trading securities	1,702	108	(528)
Net cash flow operating activities	4,222	2,590	2,253
Investing Activities:
Change in investments, primarily short term	(339)	(167)	158
Acquisition	(37)	(1,218)	(79)
Other	(229)	(373)	158
Net cash flow investing activities	(1,444)	(2,655)	(2,187)
Financing Activities:
Dividends paid	(80)	(84)	(84)
Purchases of treasury shares	(1,026)	(216)	(134)
Principal payments in debt	(1,043)	(2,411)	(3,418)
Issuance of debt	865	3,067	3,614
Other	74	(16)	(10)
Net cash flow financing activities	(2,835)	201	(166)
Net change in cash	(67)	145	(113)
Cash, beginning of year	472	327	440
Cash, end of year	405	472	327
Loews Corporation [Member]
Operating Activities:
Net income	636	1,164	654
Adjustments to reconcile net income to net cash provided (used) by operating activities:
Equity method investees	401	(405)	115
Provision for deferred income taxes	113	77	10
Changes in operating assets and liabilities, net:
Receivables	3	4	2
Accounts payable and accrued liabilities	92	(20)	52
Trading securities	1,702	100	(614)
Other, net	19	(41)	(15)
Net cash flow operating activities	2,966	879	204
Investing Activities:
Investments in and advances to subsidiaries	(135)	12	50
Change in investments, primarily short term	(187)	30	(127)
Purchase of Boardwalk Pipeline common units	(1,504)
Acquisition		(620)
Other	(2)	(1)	(2)
Net cash flow investing activities	(1,828)	(579)	(79)
Financing Activities:
Dividends paid	(80)	(84)	(84)
Purchases of treasury shares	(1,026)	(216)	(134)
Principal payments in debt			(400)
Issuance of debt			495
Other	(3)		(2)
Net cash flow financing activities	(1,109)	$ (300)	$ (125)
Net change in cash	29
Cash, end of year	$ 29