The change during the period in the entity's deferred tax assets and liabilities attributable to continuing operations as determined by applying enacted tax laws other than federal, domestic, foreign, state or local. Items affecting deferred income taxes and required to be disclosed, but not included elsewhere, would also be designated as "Other"; for example, adjustments of a deferred tax liability or asset for enacted changes in tax laws or rates or a change in the tax status of the entity and adjustments to be beginning-of-year balance of a valuation allowance because of a change in circumstance that causes a change in judgment about the realizability of the related deferred tax asset in future periods.

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

-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 6

-Section I

-Subsection 7

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 109

-Paragraph 45

-Subparagraph g, h

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 235

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.4-08.(h))

-URI http://asc.fasb.org/extlink&oid=6881521&loc=d3e23780-122690

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 08

-Paragraph h

-Article 4

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 109

-Paragraph 8, 16, 17, 289

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Deferred Tax Expense (or Benefit)

-URI http://asc.fasb.org/extlink&oid=6510177

Reference 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 740

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SAB TOPIC 6.I.7)

-URI http://asc.fasb.org/extlink&oid=6889476&loc=d3e330036-122817

Reference 8: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 740

-SubTopic 10

-Section 50

-Paragraph 9

-Subparagraph (g),(h)

-URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32639-109319

+ Details

- Definition

This item represents the total realized gain (loss) included in earnings for the period as a result of selling marketable securities categorized as trading, available-for-sale, or held-to-maturity. Additionally, this item would include any losses recognized for other than temporary impairments (OTTI) of the subject investments in debt and equity securities.

+ References+ Details

Quarterly Operating Results (Unaudited) (Details Textual) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Quarterly Operating Results Unaudited [Line Items]
Total realized gains on securities	$ 49	$ 8	$ 19		$ 29	$ 57	$ 11	$ 4	$ 76	$ 101	$ 43
Prior year development favorable (unfavorable)	27	34	(13)	21	48	14	57	39	69	158	198
Quarterly Operating Results (Unaudited) (Textual) [Abstract]
Pretax catastrophe losses			23				34
Investment in Verisk Analytics, Inc. [Member]
Quarterly Operating Results Unaudited [Line Items]
Total realized gains on securities	40		33			26
Marketform [Member]
Quarterly Operating Results Unaudited [Line Items]
Prior year development favorable (unfavorable)						(39)
Property and casualty insurance reserves [Member]
Quarterly Operating Results Unaudited [Line Items]
Special charges to increase asbestos and environmental reserves			50
Railroad and manufacturing operations [Member]
Quarterly Operating Results Unaudited [Line Items]
Special charges to increase asbestos and environmental reserves			9
Special Charges [Member]
Quarterly Operating Results Unaudited [Line Items]
Charge for valuation allowance against deferred tax assets									$ 34