Benefit Plans - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	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	$ 2,900	$ 3,200
Actuarial (gain) loss	(212)	$ 100
Future capital calls from various third party limited partnership investments	$ 99
Percentage of limited partnerships comprising of the carrying value that employ hedge fund strategies	71.30%	78.80%
Amount contributed to the savings plans	$ 100	$ 105	$ 107
Stock-based Compensation, vesting period	4 years
Stock-based Compensation, expiration period	10 years
Recognized compensation expense	$ 35	33	$ 32
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	33,923
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	235,231
Weighted average grant date fair value	$ 47.71
Stock Appreciation Rights (SARs) [Member]
Defined Benefit Plan Disclosure [Line Items]
SARs outstanding	3,470,953
Weighted average grant date fair value	$ 39.90
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	66.00%
Hedge Funds, Multi-strategy [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of hedge fund strategies	28.00%
Distressed Hedge Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of hedge fund strategies	6.00%
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Actuarial (gain) loss	$ (212)	100
Expected contribution to plan(s), next fiscal year	14
Fair value of plan assets	2,304	2,577	$ 2,423
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	82.00%	86.00%
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Actuarial (gain) loss	$ (6)	$ (1)
Fair value of plan assets	85	88	$ 86
Other Postretirement Benefits [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 0	$ 0