Increase (Decrease) In Deferred Tax Liabilities

No definition available.

Name:	trow_IncreaseDecreaseInDeferredTaxLiabilities
Namespace Prefix:	trow_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Investment Previously Accounted For As Cost Method, Increase (Decrease)

+ References

No definition available.

+ Details

Name:	trow_InvestmentPreviouslyAccountedForAsCostMethodIncreaseDecrease
Namespace Prefix:	trow_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Tax Cuts and Jobs Act of 2017, Income Tax Expense (Benefit)

+ References

No definition available.

+ Details

Name:	trow_TaxCutsAndJobsActOf2017IncomeTaxExpenseBenefit
Namespace Prefix:	trow_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Tax Cuts And Jobs Act Of 2017, Reclassification From AOCI To Retained Earnings, Foreign Currency Translation Adjustments, Tax Effect

+ References

No definition available.

+ Details

Name:	trow_TaxCutsAndJobsActOf2017ReclassificationFromAOCIToRetainedEarningsForeignCurrencyTranslationAdjustmentsTaxEffect
Namespace Prefix:	trow_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of equity securities categorized neither as held-to-maturity nor as trading.

+ References

No definition available.

+ Details

Name:	us-gaap_AvailableForSaleSecuritiesEquitySecurities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount after tax of increase (decrease) to equity or (increase) decrease to net assets, resulting from the cumulative effect adjustment of a new accounting principle applied in the period of adoption.

+ References

No definition available.

+ Details

Name:	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of income tax expense (benefit) from continuing operations attributable to an adjustment of a deferred tax liability or asset for enacted changes in tax laws or rates or a change in the tax status of the entity.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 9
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32639-109319

+ Details

Name:	us-gaap_IncomeTaxExpenseBenefitContinuingOperationsAdjustmentOfDeferredTaxAssetLiability
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Present value of lessee's discounted obligation for lease payments from operating lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 45
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=77888419&loc=SL77918627-209977

+ Details

Name:	us-gaap_OperatingLeaseLiability
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of lessee's right to use underlying asset under operating lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 45
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=77888419&loc=SL77918627-209977

+ Details

Name:	us-gaap_OperatingLeaseRightOfUseAsset
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	us-gaap_IncomeTaxAuthorityAxis=us-gaap_StateAndLocalJurisdictionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_IncomeTaxAuthorityNameAxis=trow_ComptrollerOfMarylandMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AdjustmentsForNewAccountingPronouncementsAxis=trow_AccountingStandardsUpdate201601AdjustmentForFairValueOfPreviousCostMethodInvestmentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AdjustmentsForNewAccountingPronouncementsAxis=us-gaap_AccountingStandardsUpdate201602Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementScenarioAxis=us-gaap_ScenarioForecastMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementEquityComponentsAxis=us-gaap_AccumulatedOtherComprehensiveIncomeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AdjustmentsForNewAccountingPronouncementsAxis=trow_AccountingStandardsUpdate201601AvailableForSaleSecuritiesUnrealizedGainsLossesReclassificationMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementEquityComponentsAxis=us-gaap_RetainedEarningsUnappropriatedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

BASIS OF PREPARATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES. (New Accounting Guidance and Tax Reform) (Details) - USD ($) $ in Millions		3 Months Ended		12 Months Ended
	Jan. 01, 2018	Jun. 30, 2018	Dec. 31, 2017	Dec. 31, 2018	Jan. 01, 2019	Dec. 31, 2015
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Available for sale			$ 597.1
Reclassification adjustment of stranded tax benefits on currency translation adjustments upon adoption of new accounting guidance	$ 2.3
Income tax provision related to the tax law changes		$ 20.8	$ 71.1	$ 20.8
State and local jurisdiction [Member] \| Comptroller of Maryland [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Nonrecurring income tax charge due to Maryland state tax legislation		$ 7.9
ASU 2016-01, adjustment for fair value [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Increase in investment carrying value	19.5
Increase in deferred taxes	5.0
ASU 2016-02 [Member] \| Forecast [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Right of use asset on operating lease					$ 140.0
Operating lease liability					$ 170.0
AOCI [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reclassification of accumulated other comprehensive income to retained earnings upon adoption of the new consolidation accounting guidance						$ (32.5)
AOCI [Member] \| ASU 2016-01 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reclassification of accumulated other comprehensive income to retained earnings upon adoption of the new consolidation accounting guidance	7.9
Retained earnings [Member] \| ASU 2016-01, adjustment for fair value [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reclassification of accumulated other comprehensive income to retained earnings upon adoption of the new consolidation accounting guidance	14.5
Retained earnings [Member] \| ASU 2016-01 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reclassification of accumulated other comprehensive income to retained earnings upon adoption of the new consolidation accounting guidance	$ 7.9