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SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Stock-based Compensation) (Detail) (USD $)
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Stock awards and options      
Weighted-average grant-date fair value per option awarded (in dollars per option) $ 21.12us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue $ 19.56us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue $ 16.27us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
Weighted average [Member]      
Stock awards and options      
Expected life assumption 7 years 7 years 6 years 10 months
Expected volatility assumption 30.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
31.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
32.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
Dividend yield assumption 2.20%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
2.10%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
2.10%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
Risk-free interest rate assumption 2.20%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
1.90%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
1.30%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
Stock-based compensation plan [Member]      
Stock awards and options      
Shares available for future grant (shares) 14,101,640us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant
/ us-gaap_PlanNameAxis
= us-gaap_StockCompensationPlanMember
   
Employee Stock-Based Compensation Programs [Member]      
Stock awards and options      
Stockholder-approved plans (plans) 3trow_StockholderApprovedPlansForStockOptions
/ us-gaap_PlanNameAxis
= trow_EmployeeStockBasedCompensationProgramsMember
   
Employee Stock-Based Compensation Programs [Member] | Restricted shares and restricted stock units [Member] | Weighted average [Member]      
Stock awards and options      
Graded vesting period 5 years 6 months    
Employee Stock-Based Compensation Programs [Member] | Stock options [Member] | Maximum [Member]      
Stock awards and options      
Term 10 years    
Employee Stock-Based Compensation Programs [Member] | Stock options [Member] | Weighted average [Member]      
Stock awards and options      
Graded vesting period 5 years 6 months    
Non-employee director [Member]      
Stock awards and options      
Stockholder-approved plans (plans) 2trow_StockholderApprovedPlansForStockOptions
/ us-gaap_PlanNameAxis
= trow_NonEmployeeDirectorMember
   
Non-employee director [Member] | Minimum [Member]      
Stock awards and options      
Graded vesting period 6 months    
Non-employee director [Member] | Maximum [Member]      
Stock awards and options      
Graded vesting period 1 year    
Non-employee director [Member] | Stock options [Member] | Maximum [Member]      
Stock awards and options      
Term 10 years