Commitments and Contingencies (Details) (USD $) In Thousands, unless otherwise specified	6 Months Ended	12 Months Ended
Jun. 30, 2011	Dec. 31, 2010
Insurance balances receivable	$ 653,002	$ 529,927
Past due over 90 days	5,698	2,658
Percentage of premium receivables greater than 90 days past due	0.90%	0.50%
Allied World Switzerland (Parent Guarantor) [Member]
Insurance balances receivable

Carrying amount as of the balance sheet date, net of allowance for doubtful accounts, of all premiums and other types of receivables due from other persons or entities.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 7
-Section 03
-Paragraph 5

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.5)
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Name:	us-gaap_PremiumsAndOtherReceivablesNet
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant