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Stock Compensation - Additional Information (Detail) (USD $)
In Millions, except Share data, unless otherwise specified
3 Months Ended 1 Months Ended 3 Months Ended 0 Months Ended 1 Months Ended
Mar. 31, 2015
Jun. 30, 2014
Jun. 30, 2009
Jun. 30, 2008
Mar. 31, 2014
Jan. 31, 2014
Jul. 31, 2015
Dec. 31, 1997
Jun. 25, 2014
Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                    
Stock options remaining contractual term 10 years                  
Stock Option Plan 2014                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                    
Shares available for awards under the plan 11,786,706us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant
/ us-gaap_PlanNameAxis
= aria_StockOptionPlanTwentyFourteenMember
                 
Employee Stock Purchase Plan                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                    
Reserved common stock for issuance under the plan               500,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockMember
   
Additional shares of common stock reserved   750,000aria_ShareBasedCompensationArrangementShareBasedPaymentAwardAdditionalSharesAuthorized
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockMember
750,000aria_ShareBasedCompensationArrangementShareBasedPaymentAwardAdditionalSharesAuthorized
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockMember
500,000aria_ShareBasedCompensationArrangementShareBasedPaymentAwardAdditionalSharesAuthorized
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockMember
           
Payroll withholding period for purchase of shares of common stock       3 months            
Shares of common stock issued under the plan 72,379us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockMember
      69,161us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockMember
         
Minimum | Employee Stock Purchase Plan                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                    
Purchase price of common stock by employees       85.00%aria_EmployeeStockPurchasePlanPurchasePriceAsPercentageOfMarketValue
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
           
Stock options                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                    
Stock options remaining contractual term 10 years                  
Stock options | Minimum                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                    
Stock options, vesting period 3 years                  
Stock options | Maximum                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                    
Stock options, vesting period 4 years                  
Performance share units                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                    
Number of performance share units 316,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
        997,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
    47,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
 
Award vesting percent dependent upon achievement of specific commercial objectives           50.00%us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
       
Award vesting year           2015        
Performance share units | Scenario, Forecast                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                    
Number of performance share units             121,200us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
/ us-gaap_StatementScenarioAxis
= us-gaap_ScenarioForecastMember
     
Vesting date             2015-07      
Performance share units | Maximum                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                    
Percentage of Compensation Expense 60.00%aria_PerformanceShareUnitAdditionalCompensationCostPercentage
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
                 
Stock and stock units                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                    
Total fair value of stock and stock unit awards vested 5.7us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue
/ us-gaap_AwardTypeAxis
= aria_StockAndStockUnitsMember
      2.7us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue
/ us-gaap_AwardTypeAxis
= aria_StockAndStockUnitsMember
         
Number of performance share units 3,932,423us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
/ us-gaap_AwardTypeAxis
= aria_StockAndStockUnitsMember
                3,503,153us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
/ us-gaap_AwardTypeAxis
= aria_StockAndStockUnitsMember
Restricted shares or units                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                    
Unrecognized compensation expense 16.5us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
                 
Weighted average period of compensation cost expected to be recognized 1 year 8 months 12 days