Schedule II. Condensed Financial Information of Registrant (Parent Company) (Narrative) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Parent Company
Guarantor obligations, current carrying calue	$ 5	$ 5
Guarantor obligations, maximum exposure, undiscounted	1,800
Indemnification Agreement
Guarantor obligations, maximum exposure, undiscounted	252
Indemnification Agreement \| Parent Company
Guarantor obligations, maximum exposure, undiscounted	$ 625
CNAF Consolidated \| Loews
Noncontrolling interest, ownership percentage by parent	89.00%

The current carrying amount of the liability for the freestanding or embedded guarantor's obligations under the guarantee or each group of similar guarantees.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 460
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=82913245&loc=d3e12069-110248

+ Details

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Balance Type:	credit
Period Type:	instant

- Definition

Maximum potential amount of future payments (undiscounted) the guarantor could be required to make under the guarantee or each group of similar guarantees before reduction for potential recoveries under recourse or collateralization provisions.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 460
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=82913245&loc=d3e12069-110248

+ Details

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- Definition

The parent entity's interest in net assets of the subsidiary, expressed as a percentage.

+ References

No definition available.

+ Details

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- Details

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- Details

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- Details

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- Details

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