Goodwill - Schedule of Changes in Goodwill (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013
Goodwill [Line Items]
Goodwill, beginning balance	$ 357us-gaap_Goodwill	$ 412us-gaap_Goodwill
Additions	22us-gaap_GoodwillAcquiredDuringPeriod
Impairments		(52)
Dispositions	(3)
Other adjustments	(2)us-gaap_GoodwillOtherChanges	(3)us-gaap_GoodwillOtherChanges
Goodwill, ending balance	374us-gaap_Goodwill	357us-gaap_Goodwill
CNA Financial [Member]
Goodwill [Line Items]
Goodwill, beginning balance	119	118
Other adjustments	(2)	1
Goodwill, ending balance	117	119
Diamond Offshore [Member]
Goodwill [Line Items]
Goodwill, beginning balance		20
Impairments
Other adjustments
Goodwill, ending balance	20	20
Boardwalk Pipeline [Member]
Goodwill [Line Items]
Goodwill, beginning balance	215	271
Additions	22
Impairments		(52)
Other adjustments		(4)
Goodwill, ending balance	237	215
Loews Hotels [Member]
Goodwill [Line Items]
Goodwill, beginning balance	3	3
Impairments
Dispositions	(3)
Other adjustments
Goodwill, ending balance		$ 3

Goodwill impairment loss from continuing operation.

No definition available.

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- Definition

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 20

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 20

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6388280&loc=d3e13770-109266

+ Details

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- Definition

Amount of increase in asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized resulting from a business combination.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267

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- Definition

Amount of other (increase) decrease of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (g)

-URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267

+ Details

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- Definition

Amount of divestiture of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (d)

-URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267

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