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Shareholders' Equity (Narrative) (Details) (USD $)
12 Months Ended 0 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Jul. 09, 2013
May 01, 2014
May 02, 2013
Class of Stock [Line Items]            
Stock Repurchased and Retired During Period, Shares 2,702,196us-gaap_StockRepurchasedAndRetiredDuringPeriodShares          
Treasury Stock, Shares, Acquired 4,906,785us-gaap_TreasuryStockSharesAcquired 5,544,432us-gaap_TreasuryStockSharesAcquired 10,967,877us-gaap_TreasuryStockSharesAcquired      
Common stock, shares outstanding 96,195,482us-gaap_CommonStockSharesOutstanding 100,253,646us-gaap_CommonStockSharesOutstanding        
Shares cancelled, shares 2,702,196us-gaap_TreasuryStockSharesRetired 5,632,152us-gaap_TreasuryStockSharesRetired        
Maximum percentage of registered capital in treasury shares 10.00%awh_MaximumAllowablePercentageOfCapitalInTreasurySharesWithoutPriorShareholderAuthorization          
Allied World Switzerland (Parent Guarantor)            
Class of Stock [Line Items]            
Threshold for dividend restrictions 20.00%awh_CapitalReserveRestrictionThresholdForAnnualProfitRetention
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
         
Minimum Annual Profit Percentage Required 5.00%awh_MinimumAnnualProfitPercentageRequired
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
         
Nonvoting common stock            
Class of Stock [Line Items]            
Shares cancelled, shares       87,720us-gaap_TreasuryStockSharesRetired
/ us-gaap_StatementClassOfStockAxis
= us-gaap_NonvotingCommonStockMember
   
Common shares repurchased and constructively retired            
Class of Stock [Line Items]            
Shares cancelled, shares       4,616,058us-gaap_TreasuryStockSharesRetired
/ us-gaap_StatementClassOfStockAxis
= awh_CommonSharesRepurchasedAndConstructivelyRetiredMember
   
Common shares            
Class of Stock [Line Items]            
Dividends declared per share         $ 0.225us-gaap_CommonStockDividendsPerShareDeclared
/ us-gaap_StatementClassOfStockAxis
= us-gaap_CommonStockMember
$ 0.167us-gaap_CommonStockDividendsPerShareDeclared
/ us-gaap_StatementClassOfStockAxis
= us-gaap_CommonStockMember