General	6 Months Ended
Jun. 30, 2013
General [Abstract]
General	1. GENERAL Allied World Assurance Company Holdings, AG, a Swiss holding company (“Allied World Switzerland”), through its wholly-owned subsidiaries (collectively, the “Company”), provides property and casualty insurance and reinsurance on a worldwide basis through operations in Bermuda, the United States, Europe, Hong Kong and Singapore. References to $ are to the lawful currency of the United States and to CHF are to the lawful currency of Switzerland.

The entire disclosure for the nature of an entity's business, the major products or services it sells or provides and its principal markets, including the locations of those markets. If the entity operates in more than one business, the disclosure also indicates the relative importance of its operations in each business and the basis for the determination (for example, assets, revenues, or earnings).

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 275

-SubTopic 10

-Section 50

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6927468&loc=d3e6003-108592

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

-Publisher AICPA

-Name Statement of Position (SOP)

-Number 94-6

-Paragraph 10

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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.

Name:	us-gaap_NatureOfOperations
Namespace Prefix:	us-gaap_
Data Type:	nonnum:textBlockItemType
Balance Type:	na
Period Type:	duration