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Shareholders' Equity - Ordinary Shares (Details) (USD $)
Share data in Millions, except Per Share data, unless otherwise specified
12 Months Ended 1 Months Ended 33 Months Ended 1 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Jan. 31, 2010
Apr. 30, 2012
Dec. 31, 2014
Nov. 30, 2014
Common Stock Programs              
Cost of shares repurchased $ 2,250,000,000us-gaap_TreasuryStockValueAcquiredCostMethod $ 1,102,000,000us-gaap_TreasuryStockValueAcquiredCostMethod $ 1,125,000,000us-gaap_TreasuryStockValueAcquiredCostMethod        
Share Repurchase Program [Member]              
Common Stock Programs              
Number of shares repurchased (in shares) 25.8us-gaap_TreasuryStockSharesAcquired
/ aon_OrdinaryShareProgramsAxis
= aon_ShareRepurchaseProgramMember
16.8us-gaap_TreasuryStockSharesAcquired
/ aon_OrdinaryShareProgramsAxis
= aon_ShareRepurchaseProgramMember
         
Average price per share of shares purchased under share repurchase program (in dollars per share) $ 87.18us-gaap_TreasuryStockAcquiredAverageCostPerShare
/ aon_OrdinaryShareProgramsAxis
= aon_ShareRepurchaseProgramMember
$ 65.65us-gaap_TreasuryStockAcquiredAverageCostPerShare
/ aon_OrdinaryShareProgramsAxis
= aon_ShareRepurchaseProgramMember
         
Cost of shares repurchased 2,300,000,000us-gaap_TreasuryStockValueAcquiredCostMethod
/ aon_OrdinaryShareProgramsAxis
= aon_ShareRepurchaseProgramMember
1,100,000,000us-gaap_TreasuryStockValueAcquiredCostMethod
/ aon_OrdinaryShareProgramsAxis
= aon_ShareRepurchaseProgramMember
         
Share Repurchase Programs of 2012 and 2014 [Member]              
Common Stock Programs              
Share repurchase, remaining authorization limit 5,600,000,000us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount
/ aon_OrdinaryShareProgramsAxis
= aon_ShareRepurchaseProgramsof2012and2014Member
           
2010 - Share Repurchase Program [Member]              
Common Stock Programs              
Share repurchase authorization limit       2,000,000,000us-gaap_StockRepurchaseProgramAuthorizedAmount
/ aon_OrdinaryShareProgramsAxis
= aon_ShareRepurchaseProgramOf2010Member
     
2012 - Share Repurchase Program [Member]              
Common Stock Programs              
Share repurchase authorization limit         5,000,000,000us-gaap_StockRepurchaseProgramAuthorizedAmount
/ aon_OrdinaryShareProgramsAxis
= aon_ShareRepurchaseProgramOf2012Member
   
Number of shares repurchased (in shares)           62.1us-gaap_TreasuryStockSharesAcquired
/ aon_OrdinaryShareProgramsAxis
= aon_ShareRepurchaseProgramOf2012Member
 
Cost of shares repurchased           4,400,000,000us-gaap_TreasuryStockValueAcquiredCostMethod
/ aon_OrdinaryShareProgramsAxis
= aon_ShareRepurchaseProgramOf2012Member
 
2014 - Share Repurchase Program [Member]              
Common Stock Programs              
Share repurchase authorization limit             $ 5,000,000,000us-gaap_StockRepurchaseProgramAuthorizedAmount
/ aon_OrdinaryShareProgramsAxis
= aon_ShareRepurchaseProgramof2014Member