Schedule I - Condensed Financial Information of Registrant - Parent Company Only, Statements of Cash Flows (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating Activities:
Net income	$ 871	$ 706	$ 1,412
Adjustments to reconcile net income to net cash provided (used) by operating activities:
Equity method investees	20	572	25
Provision for deferred income taxes	70	86	(47)
Changes in operating assets and liabilities, net:
Receivables	114	(131)	93
Trading securities	(494)	1,702	108
Net cash flow provided by operating activities	1,741	4,222	2,590
Investing Activities:
Change in investments, primarily short term	(57)	(339)	(167)
Acquisition	(257)	(37)	(1,218)
Other	(178)	(229)	(373)
Net cash flow used by investing activities	(671)	(1,444)	(2,655)
Financing Activities:
Dividends paid	(76)	(80)	(84)
Purchases of treasury shares	(1,051)	(1,026)	(216)
Other	(16)	74	(16)
Net cash flow (used) provided by financing activities	(1,144)	(2,835)	201
Net change in cash	(69)	(67)	145
Cash, beginning of year	405	472	327
Cash, end of year	336	405	472
Loews Corporation [Member]
Operating Activities:
Net income	932	636	1,164
Adjustments to reconcile net income to net cash provided (used) by operating activities:
Equity method investees	36	401	(405)
Provision for deferred income taxes	106	113	77
Changes in operating assets and liabilities, net:
Receivables	1	3	4
Accounts payable and accrued liabilities	(29)	92	(20)
Trading securities	(478)	1,702	100
Other, net	36	19	(41)
Net cash flow provided by operating activities	604	2,966	879
Investing Activities:
Investments in and advances to subsidiaries	183	(135)	12
Change in investments, primarily short term	326	(187)	30
Purchase of Boardwalk Pipelines common units		(1,504)
Acquisition			(620)
Other		(2)	(1)
Net cash flow used by investing activities	509	(1,828)	(579)
Financing Activities:
Dividends paid	(76)	(80)	(84)
Purchases of treasury shares	(1,051)	(1,026)	(216)
Other	(5)	(3)
Net cash flow (used) provided by financing activities	(1,132)	(1,109)	$ (300)
Net change in cash	(19)	29
Cash, beginning of year	29
Cash, end of year	$ 10	$ 29