Benefit Plans - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Eligible age for several postretirement benefit plans	55 years
Eligible age for Medicare benefits	65 years
Accumulated benefit obligation for all defined benefit pension plans	$ 3,100	$ 2,900
Actuarial (gain) loss	300	$ (212)
Future capital calls from various third party limited partnership investments	$ 111
Percentage of limited partnerships comprising of the carrying value that employ hedge fund strategies	65.70%	71.30%
Amount contributed to the savings plans	$ 102	$ 100	$ 105
Stock-based Compensation, vesting period	4 years
Stock-based Compensation, expiration period	10 years
Recognized compensation expense	$ 37	35	33
Time-based Restricted Stock Units (RSUs) [Member]
Defined Benefit Plan Disclosure [Line Items]
Terms of Award	right to receive one share of the Company’s common stock for each vested RSU
Forfeited during the year	3,621
Performance-based Restricted Stock Units (PSUs) [Member]
Defined Benefit Plan Disclosure [Line Items]
Terms of Award	receive one share of the Company’s common stock for each vested PSU
Restricted Stock Units (RSUs) and Performance Stock Units (PSUs) [Member]
Defined Benefit Plan Disclosure [Line Items]
Grants In Period	216,802
Weighted average grant date fair value	$ 48.10
Stock Appreciation Rights (SARs) [Member]
Defined Benefit Plan Disclosure [Line Items]
SARs outstanding	2,469,756
Weighted average grant date fair value	$ 41.11
2016 Loews Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Stock-based Compensation, number of shares authorized				6,000,000
Stock-based Compensation, maximum number of shares to be granted to each individual				500,000
Maximum [Member] | 2016 Loews Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Stock-based Compensation, number of shares to be forfeited under prior plan				3,000,000
Second Anniversary [Member] | Time-based Restricted Stock Units (RSUs) [Member]
Defined Benefit Plan Disclosure [Line Items]
vesting percentage				50.00%
Second Anniversary [Member] | Performance-based Restricted Stock Units (PSUs) [Member]
Defined Benefit Plan Disclosure [Line Items]
vesting percentage				50.00%
Third Anniversary [Member] | Time-based Restricted Stock Units (RSUs) [Member]
Defined Benefit Plan Disclosure [Line Items]
vesting percentage				50.00%
Third Anniversary [Member] | Performance-based Restricted Stock Units (PSUs) [Member]
Defined Benefit Plan Disclosure [Line Items]
vesting percentage				50.00%
Defined Benefit Plan, Equity Securities [Member] | Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Target allocation of plan assets invested in equity securities and limited partnerships, Maximum	40.00%
Defined Benefit Plan, Equity Securities [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Target allocation of plan assets invested in equity securities and limited partnerships, Maximum	60.00%
Hedge Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of hedge fund strategies	62.00%
Hedge Funds, Multi-strategy [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of hedge fund strategies	31.00%
Distressed Hedge Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of hedge fund strategies	7.00%
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Actuarial (gain) loss	$ 299	(212)
Expected contribution to plan(s), next fiscal year	14
Fair value of plan assets	2,576	2,304	2,577
Pension Benefits [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	10	$ 10
Postretirement Healthcare and Life Insurance Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected contribution to plan(s), next fiscal year	$ 2
Defined Benefit Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of limited partnerships comprising of the carrying value that employ hedge fund strategies	80.00%	82.00%
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Actuarial (gain) loss	$ 3	$ (6)
Fair value of plan assets	90	85	$ 88
Other Postretirement Benefits [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 0	$ 0