This item represents the difference between the gross realized gains and losses realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities. Additionally, this item would include any losses recognized for other than temporary impairments (OTTI) of the subject investments in debt and equity securities.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 9
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27357-111563

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- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=64930739&loc=d3e28878-108400

Reference 2: http://www.xbrl.org/2003/role/presentationRef
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-Topic 835
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-Section 45
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- Definition

The amount of early contract termination fees included in liabilities subject to compromise.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 852
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 852
-SubTopic 10
-Section 55
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-Name Accounting Standards Codification
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-Section 45
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- Definition

Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.1)
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Total revenue from sale of goods and services rendered during the reporting period, in the normal course of business, reduced by sales returns and allowances, and sales discounts.

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Business Segments (Revenues by Line of Business) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues	$ 2,448	$ 2,398	$ 2,366	$ 2,330	$ 2,390	$ 2,433	$ 2,348	$ 2,195	$ 9,542	$ 9,366	$ 9,101
Total operating revenues									9,449	9,316	9,168
Net realized investment gains (losses)									93	50	(67)
Loss on early redemption	42								42
Management & Professional Liability
Revenues									2,591	2,617	2,647
Surety
Revenues									541	529	504
Warranty & Alternative Risks
Revenues									551	511	461
Specialty
Revenues									3,683	3,657	3,612
Middle Market
Revenues									1,907	1,768	1,641
Small Business
Revenues									480	582	621
Other Commercial Insurance
Revenues									1,126	1,124	1,156
Commercial
Revenues									3,513	3,474	3,418
Canada
Revenues									224	203	213
CNA Europe
Revenues									326	314	311
Hardy
Revenues									359	340	331
International
Revenues									909	857	855
Life & Group
Revenues									1,323	1,301	1,259
Corporate & Other
Revenues									22	28	29
Eliminations
Revenues									(1)	$ (1)	$ (5)
Senior Notes, Due November 2019
Face amount	$ 350								$ 350