Debt - Schedule of Long-Term Debt Instruments (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Debt Instrument [Line Items]
Debt, Gross	$ 10,736us-gaap_DebtInstrumentCarryingAmount	$ 10,409us-gaap_DebtInstrumentCarryingAmount
Less unamortized discount	68	65
Debt	10,668	10,344
Loews Corporation [Member]
Debt Instrument [Line Items]
Debt, Gross	1,700
Less unamortized discount	20
CNA Financial [Member]
Debt Instrument [Line Items]
Debt, Gross	2,575
Less unamortized discount	14
Capital lease obligation	2
Diamond Offshore [Member]
Debt Instrument [Line Items]
Debt, Gross	2,250
Less unamortized discount	19
Boardwalk Pipeline [Member]
Debt Instrument [Line Items]
Debt, Gross	3,705
Less unamortized discount	15
Capital lease obligation	10	10
Loews Hotels [Member]
Debt Instrument [Line Items]
Debt, Gross	506	202
5.3% Notes Due 2016 [Member] \| Loews Corporation [Member]
Debt Instrument [Line Items]
Debt, Gross	400	400
2.6% Notes Due 2023 [Member] \| Loews Corporation [Member]
Debt Instrument [Line Items]
Debt, Gross	500	500
6.0% Notes Due 2035 [Member] \| Loews Corporation [Member]
Debt Instrument [Line Items]
Debt, Gross	300	300
4.1% Notes Due 2043 [Member] \| Loews Corporation [Member]
Debt Instrument [Line Items]
Debt, Gross	500	500
5.9% Notes Due 2014 [Member] \| CNA Financial [Member]
Debt Instrument [Line Items]
Debt, Gross		549
6.5% Notes Due 2016 [Member] \| CNA Financial [Member]
Debt Instrument [Line Items]
Debt, Gross	350	350
7.0% Notes Due 2018 [Member] \| CNA Financial [Member]
Debt Instrument [Line Items]
Debt, Gross	150	150
7.4% Notes Due 2019 [Member] \| CNA Financial [Member]
Debt Instrument [Line Items]
Debt, Gross	350	350
5.9% Notes Due 2020 [Member] \| CNA Financial [Member]
Debt Instrument [Line Items]
Debt, Gross	500	500
5.8% Notes Due 2021 [Member] \| CNA Financial [Member]
Debt Instrument [Line Items]
Debt, Gross	400	400
7.3% Debentures Due 2023 [Member] \| CNA Financial [Member]
Debt Instrument [Line Items]
Debt, Gross	243	243
4.0% Notes Due 2024 [Member] \| CNA Financial [Member]
Debt Instrument [Line Items]
Debt, Gross	550
Variable Rate Note Due 2036 [Member] \| CNA Financial [Member]
Debt Instrument [Line Items]
Debt, Gross	30	30
5.2% Notes Due 2014 [Member] \| Diamond Offshore [Member]
Debt Instrument [Line Items]
Debt, Gross		250
4.9% Notes Due 2015 [Member] \| Diamond Offshore [Member]
Debt Instrument [Line Items]
Debt, Gross	250	250
5.9% Notes Due 2019 [Member] \| Diamond Offshore [Member]
Debt Instrument [Line Items]
Debt, Gross	500	500
3.5% Senior Notes Due 2023 [Member] \| Diamond Offshore [Member]
Debt Instrument [Line Items]
Debt, Gross	250	250
5.7% Notes Due 2039 [Member] \| Diamond Offshore [Member]
Debt Instrument [Line Items]
Debt, Gross	500	500
4.9% Notes Due 2043 [Member] \| Diamond Offshore [Member]
Debt Instrument [Line Items]
Debt, Gross	750	750
Variable Rate Revolving Credit Facility Due 2017 [Member] \| Boardwalk Pipeline [Member]
Debt Instrument [Line Items]
Debt, Gross	120	175
Variable Rate Term Loan Due 2017 [Member] \| Boardwalk Pipeline [Member]
Debt Instrument [Line Items]
Debt, Gross	200	225
4.6% Notes Due 2015 [Member] \| Boardwalk Pipeline [Member]
Debt Instrument [Line Items]
Debt, Gross	250	250
5.1% Notes Due 2015 [Member] \| Boardwalk Pipeline [Member]
Debt Instrument [Line Items]
Debt, Gross	275	275
5.9% Notes Due 2016 [Member] \| Boardwalk Pipeline [Member]
Debt Instrument [Line Items]
Debt, Gross	250	250
5.5% Notes Due 2017 [Member] \| Boardwalk Pipeline [Member]
Debt Instrument [Line Items]
Debt, Gross	300	300
6.3% Notes Due 2017 [Member] \| Boardwalk Pipeline [Member]
Debt Instrument [Line Items]
Debt, Gross	275	275
5.2% Notes Due 2018 [Member] \| Boardwalk Pipeline [Member]
Debt Instrument [Line Items]
Debt, Gross	185	185
5.8% Notes Due 2019 [Member] \| Boardwalk Pipeline [Member]
Debt Instrument [Line Items]
Debt, Gross	350	350
4.5% Notes Due 2021 [Member] \| Boardwalk Pipeline [Member]
Debt Instrument [Line Items]
Debt, Gross	440	440
4.0% Notes Due 2022 [Member] \| Boardwalk Pipeline [Member]
Debt Instrument [Line Items]
Debt, Gross	300	300
3.4% Notes Due 2023 [Member] \| Boardwalk Pipeline [Member]
Debt Instrument [Line Items]
Debt, Gross	300	300
5.0% Notes Due 2024 [Member] \| Boardwalk Pipeline [Member]
Debt Instrument [Line Items]
Debt, Gross	350
7.3% Debentures Due 2027 [Member] \| Boardwalk Pipeline [Member]
Debt Instrument [Line Items]
Debt, Gross	$ 100	$ 100

Long Term Debt Current Non Current Including Capital Lease Obligations

No definition available.

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Namespace Prefix:	l_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount equal to the present value (the principal) at the beginning of the lease term of minimum lease payments during the lease term (excluding that portion of the payments representing executory costs such as insurance, maintenance, and taxes to be paid by the lessor, together with any profit thereon) net of payments or other amounts applied to the principal through the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 16

-Article 7

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 840

-SubTopic 30

-Section 50

-Paragraph 1

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6455398&loc=d3e45280-112737

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of long-term debt before deduction of unamortized discount or premium. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt, with initial maturities beyond one year or the normal operating cycle, if longer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 20

-Article 5

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.22)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 16

-Article 9

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant