Exercise Price of Options Issued Not Be Less than the Percentage of Fair Market Value of the Common Shares Granted

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- Definition

Percentage of Weighted Average Annual Forfeiture Rate Determining in Compensation Expense over the Service Period

+ Details

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- Definition

The performance period percentage expensed for the performance based units granted.

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- Definition

Share based compensation arrangement by share based payment award options expire in years.

+ Details

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- Definition

Excess of issue price over par or stated value of the entity's capital stock and amounts received from other transactions involving the entity's stock or stockholders. Includes adjustments to additional paid in capital. Some examples of such adjustments include recording the issuance of debt with a beneficial conversion feature and certain tax consequences of equity instruments awarded to employees. Use this element for the aggregate amount of additional paid-in capital associated with common and preferred stock. For additional paid-in capital associated with only common stock, use the element additional paid in capital, common stock. For additional paid-in capital associated with only preferred stock, use the element additional paid in capital, preferred stock.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 31

-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 210.5-02.30(a)(1))

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

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- Definition

Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 1

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5047-113901

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (h)(1)(i)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph g(1)

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SAB TOPIC 14.F)

-URI http://asc.fasb.org/extlink&oid=6793087&loc=d3e301413-122809

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

-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 14

-Section F

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph 64

-Subparagraph b

-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.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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- Definition

The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested).

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph a

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (a)(3)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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Employee Benefit Plans (Narrative) (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended			3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended			9 Months Ended	12 Months Ended		3 Months Ended		9 Months Ended		12 Months Ended				3 Months Ended		9 Months Ended				9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010	Dec. 31, 2010	Sep. 30, 2011 General And Administrative Expense [Member] Employee Stock Option [Member]	Sep. 30, 2010 General And Administrative Expense [Member] Employee Stock Option [Member]	Sep. 30, 2011 General And Administrative Expense [Member] Employee Stock Option [Member]	Sep. 30, 2010 General And Administrative Expense [Member] Employee Stock Option [Member]	Sep. 30, 2011 RSUs [Member]	Sep. 30, 2010 RSUs [Member]	Sep. 30, 2011 RSUs [Member]	Sep. 30, 2010 RSUs [Member]	Dec. 31, 2010 RSUs [Member]	Sep. 30, 2011 RSUs [Member] Allied World Switzerland (Parent Guarantor) [Member]	Dec. 31, 2010 RSUs [Member] Allied World Switzerland (Parent Guarantor) [Member]	Dec. 31, 2009 RSUs [Member] Allied World Switzerland (Parent Guarantor) [Member]	Sep. 30, 2011 LTIP Award [Member]	Sep. 30, 2010 LTIP Award [Member]	Sep. 30, 2011 LTIP Award [Member]	Sep. 30, 2010 LTIP Award [Member]	Dec. 31, 2008 LTIP Award [Member]	Dec. 31, 2010 LTIP Award [Member]	Sep. 30, 2011 2001 Employee Stock Option Plan [Member]	Sep. 30, 2011 2004 Stock Incentive Plan [Member]	Sep. 30, 2011 Cash-Equivalent Stock Awards [Member]	Sep. 30, 2010 Cash-Equivalent Stock Awards [Member]	Sep. 30, 2011 Cash-Equivalent Stock Awards [Member]	Sep. 30, 2010 Cash-Equivalent Stock Awards [Member]	Sep. 30, 2011 Employee Stock Option [Member]	Dec. 31, 2010 Employee Stock Option [Member]	Sep. 30, 2011 Employee Stock Option [Member] Allied World Switzerland (Parent Guarantor) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options expire in years			10
Common shares, issued																		2,000,000		2,000,000				4,000,000	2,000,000
Exercise price of options issued not be less than percentage of fair market value of the common shares granted																																100.00%
Percentage of weighted average annual forfeiture rate used in determining in compensation expense over the service period												2.80%																		6.72%
Amount of compensation expense recorded	$ 7,853	$ 12,490	$ 28,540	$ 35,265		$ 967	$ 706	$ 3,143	$ 2,256	$ 2,698	$ 3,174	$ 10,227	$ 10,215					$ 1,140	$ 3,843	$ 3,547	$ 12,706					$ 3,048	$ 4,767	$ 11,623	$ 10,088
Additional paid-in capital	$ 73,797		$ 73,797		$ 170,239					$ 25,362		$ 25,362		$ 37,991				$ 47,991		$ 47,991			$ 77,728							$ 42,017	$ 41,505
Expense related to unvested awards in percentage of fair value															100.00%	100.00%	150.00%					150.00%