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Stock Compensation - Additional Information (Detail) (USD $)
In Millions, except Share data, unless otherwise specified
12 Months Ended 1 Months Ended 12 Months Ended 0 Months Ended 1 Months Ended
Dec. 31, 2014
Jun. 30, 2014
Jun. 30, 2009
Jun. 30, 2008
Dec. 31, 2013
Dec. 31, 2012
Jan. 31, 2014
Jul. 31, 2014
Jul. 31, 2013
Mar. 31, 2012
Jul. 31, 2015
Dec. 31, 1997
Jun. 25, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                          
Stock options remaining contractual term 10 years                        
Total unrecognized compensation cost related to non vested stock options outstanding $ 21.4us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions                        
Stock Option Plan 2014                          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                          
Shares available for awards under the plan 13,840,313us-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 250,776us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockMember
      101,300us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockMember
66,531us-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                        
Weighted average period of compensation cost expected to be recognized 2 years 2 months 12 days                        
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
Number of performance share units vested in period               129,200us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
274,400us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
       
Vesting date               2014-07 2013-07        
Number of performance share units granted in period                   524,800us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ 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 5.2us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue
/ us-gaap_AwardTypeAxis
= aria_StockAndStockUnitsMember
      25.5us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue
/ us-gaap_AwardTypeAxis
= aria_StockAndStockUnitsMember
27.8us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue
/ us-gaap_AwardTypeAxis
= aria_StockAndStockUnitsMember
             
Number of performance share units 3,503,153us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
/ us-gaap_AwardTypeAxis
= aria_StockAndStockUnitsMember
      2,047,600us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
/ us-gaap_AwardTypeAxis
= aria_StockAndStockUnitsMember
               
Number of performance share units vested in period 702,229us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod
/ us-gaap_AwardTypeAxis
= aria_StockAndStockUnitsMember
                       
Number of performance share units granted in period 2,479,500us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= aria_StockAndStockUnitsMember
                       
Restricted shares or units                          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                          
Weighted average period of compensation cost expected to be recognized 1 year 6 months                        
Unrecognized compensation expense $ 19.3us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember