Label	Element	Value
Prospectus [Line Items]	rr_ProspectusLineItems
Document Type	dei_DocumentType	485BPOS
Document Period End Date	dei_DocumentPeriodEndDate	Dec. 31, 2018
Entity Registrant Name	dei_EntityRegistrantName	PUTNAM FUNDS TRUST
Entity Central Index Key	dei_EntityCentralIndexKey	0001005942
Amendment Flag	dei_AmendmentFlag	false
Entity Inv Company Type	dei_EntityInvCompanyType	N-1A
Trading Symbol	dei_TradingSymbol	PFT
Document Creation Date	dei_DocumentCreationDate	Nov. 26, 2019
Document Effective Date	dei_DocumentEffectiveDate	Nov. 30, 2019
Prospectus Date	rr_ProspectusDate	Nov. 30, 2019
Putnam Ultra Short Duration Income Fund*
Prospectus [Line Items]	rr_ProspectusLineItems
Risk/Return [Heading]	rr_RiskReturnHeading	Fund summary
Footnote	PFT_Footnotetext	*Prior to June 1, 2019, the fund was known as Putnam Short Duration Income Fund.
Objective [Heading]	rr_ObjectiveHeading	Goal
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	Putnam Ultra Short Duration Income Fund seeks as high a rate of current income as Putnam Investment Management, LLC believes is consistent with preservation of capital and maintenance of liquidity.
Expense [Heading]	rr_ExpenseHeading	Fees and expenses
Expense Narrative [Text Block]	rr_ExpenseNarrativeTextBlock	The following tables describe the fees and expenses you may pay if you buy and hold shares of the fund. Information about sales charge discounts is available from your financial advisor and in the Appendix to the fund’s prospectus.
Shareholder Fees Caption [Text]	rr_ShareholderFeesCaption	Shareholder fees (fees paid directly from your investment)
Operating Expenses Caption [Text]	rr_OperatingExpensesCaption	Annual fund operating expenses (expenses you pay each year as a percentage of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	November 30, 2020.
Portfolio Turnover [Heading]	rr_PortfolioTurnoverHeading	Portfolio turnover
Portfolio Turnover [Text Block]	rr_PortfolioTurnoverTextBlock	The fund pays transaction-related costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher turnover rate may indicate higher transaction costs and may result in higher taxes when the fund’s shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or the above example, affect fund performance. The fund’s turnover rate in the most recent fiscal year was 27%.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	27.00%
Expense Example [Heading]	rr_ExpenseExampleHeading	Example
Expense Example Narrative [Text Block]	rr_ExpenseExampleNarrativeTextBlock	The following hypothetical example is intended to help you compare the cost of investing in the fund with the cost of investing in other funds. It assumes that you invest $10,000 in the fund for the time periods indicated and then, except as indicated, redeem or hold all your shares at the end of those periods. It assumes a 5% return on your investment each year and that the fund’s operating expenses remain the same. Only the first year of each period in the example takes into account the expense reimbursement described above. Your actual costs may be higher or lower.
Strategy [Heading]	rr_StrategyHeading	Investments, risks, and performance
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	Investments We invest in a diversified portfolio of fixed income securities comprised of short duration, investment-grade money market and other fixed income securities. The fund’s investments may include obligations of the U.S. government, its agencies and instrumentalities, which are backed by the full faith and credit of the United States (e.g., U.S. Treasury bonds and Ginnie Mae mortgage-backed bonds) or by only the credit of a federal agency or government-sponsored entity (e.g., Fannie Mae or Freddie Mac mortgage-backed bonds), domestic corporate debt obligations, taxable municipal debt securities, securitized debt instruments (such as mortgage- and asset-backed securities), repurchase agreements, certificates of deposit, bankers acceptances, commercial paper (including asset-backed commercial paper), time deposits, Yankee Eurodollar securities and other money market instruments. We may also invest in U.S. dollar-denominated foreign securities of these types. Under normal circumstances, the effective duration of the fund’s portfolio will generally not be greater than one year. Effective duration provides a measure of a fund’s interest-rate sensitivity. The longer a fund’s duration, the more sensitive the fund is to shifts in interest rates. Under normal circumstances, the dollar-weighted average portfolio maturity of the fund is not expected to exceed three and one-half years. We may consider, among other factors, credit, interest rate and prepayment risks, as well as general market conditions, when deciding whether to buy or sell investments. We may also use derivatives, such as futures, options and swap contracts, for both hedging and non-hedging purposes.
Risk [Heading]	rr_RiskHeading	Risks
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	It is important to understand that you can lose money by investing in the fund. The effects of inflation may erode the value of your investment over time. The value of investments in the fund’s portfolio may fall or fail to rise over extended periods of time for a variety of reasons, including general economic, political or financial market conditions, investor sentiment and market perceptions, government actions, geopolitical events or changes, and factors related to a specific issuer, geography, industry, or sector. These and other factors may lead to increased volatility and reduced liquidity in the fund’s portfolio holdings. The risks associated with fixed-income investments include interest rate risk, which means the value of the fund’s investments is likely to fall if interest rates rise. Fixed income investments are also subject to credit risk, which is the risk that the issuer of a fixed income investment may default on payment of interest or principal. Credit risk is generally greater for debt not backed by the full faith and credit of the U.S. government, and interest rate risk is generally greater for longer-term debt. Mortgage-backed investments, unlike traditional debt investments, are also subject to prepayment risk, which means that they may increase in value less than other bonds when interest rates decline and decline in value more than other bonds when interest rates rise. We may have to invest the proceeds from prepaid investments, including mortgage-backed investments, in other investments with less attractive terms and yields. Our use of derivatives may increase the risks of investing in the fund by increasing investment exposure (which may be considered leverage) or, in the case of many over-the-counter instruments, because of the potential inability to terminate or sell derivatives positions and the potential failure of the other party to the instrument to meet its obligations. The fund may not achieve its goal, and it is not intended to be a complete investment program. An investment in the fund is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Risk Lose Money [Text]	rr_RiskLoseMoney	It is important to understand that you can lose money by investing in the fund.
Risk Not Insured Depository Institution [Text]	rr_RiskNotInsuredDepositoryInstitution	An investment in the fund is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	Performance
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	The performance information below gives some indication of the risks associated with an investment in the fund by showing the fund’s performance year to year and over time. The bar chart does not reflect the impact of sales charges. If it did, performance would be lower. Please remember that past performance is not necessarily an indication of future results. Monthly performance figures for the fund are available at putnam.com.
Performance Information Illustrates Variability of Returns [Text]	rr_PerformanceInformationIllustratesVariabilityOfReturns	The performance information below gives some indication of the risks associated with an investment in the fund by showing the fund’s performance year to year and over time.
Performance Availability Website Address [Text]	rr_PerformanceAvailabilityWebSiteAddress	putnam.com
Performance Past Does Not Indicate Future [Text]	rr_PerformancePastDoesNotIndicateFuture	Please remember that past performance is not necessarily an indication of future results.
Bar Chart [Heading]	rr_BarChartHeading	Annual total returns for class A shares before sales charges
Bar Chart Does Not Reflect Sales Loads [Text]	rr_BarChartDoesNotReflectSalesLoads	The bar chart does not reflect the impact of sales charges. If it did, performance would be lower.
Bar Chart Closing [Text Block]	rr_BarChartClosingTextBlock	Year-to-date performance through 9/30/19  2.23% Best calendar quarter Q3 2018   0.56% Worst calendar quarter Q3 2015 −0.10%
Year to Date Return, Label	rr_YearToDateReturnLabel	Year-to-date performance
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Sep. 30, 2019
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	2.23%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	Best calendar quarter
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Sep. 30, 2018
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	0.56%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	Worst calendar quarter
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Sep. 30, 2015
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(0.10%)
Performance Table Heading	rr_PerformanceTableHeading	Average annual total returns after sales charges (for periods ended 12/31/18)
Performance Table Uses Highest Federal Rate	rr_PerformanceTableUsesHighestFederalRate	After-tax returns reflect the historical highest individual federal marginal income tax rates and do not reflect state and local taxes.
Performance Table Not Relevant to Tax Deferred	rr_PerformanceTableNotRelevantToTaxDeferred	Actual after-tax returns depend on an investor's tax situation and may differ from those shown.
Performance Table One Class of after Tax Shown [Text]	rr_PerformanceTableOneClassOfAfterTaxShown	After-tax returns are shown for class A shares only and will vary for other classes.
Performance Table Closing [Text Block]	rr_PerformanceTableClosingTextBlock	ICE BofAML Indexes: ICE Data Indices, LLC (“ICE BofAML”), used with permission. ICE BofAML permits use of the ICE BofAML indices and related data on an “as is” basis; makes no warranties regarding same; does not guarantee the suitability, quality, accuracy, timeliness, and/or completeness of the ICE BofAML indices or any data included in, related to, or derived therefrom; assumes no liability in connection with the use of the foregoing; and does not sponsor, endorse, or recommend Putnam Investments, or any of its products or services. After-tax returns reflect the historical highest individual federal marginal income tax rates and do not reflect state and local taxes. Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. After-tax returns are shown for class A shares only and will vary for other classes. These after-tax returns do not apply if you hold your fund shares through a 401(k) plan, an IRA, or another tax-advantaged arrangement.
Putnam Ultra Short Duration Income Fund* | ICE BofAML U.S. Treasury Bill Index (no deduction for fees, expenses or taxes)
Prospectus [Line Items]	rr_ProspectusLineItems
1 Year	rr_AverageAnnualReturnYear01	1.88%
5 Years	rr_AverageAnnualReturnYear05	0.64%
Since Inception	rr_AverageAnnualReturnSinceInception	0.47%
Putnam Ultra Short Duration Income Fund* | Class A
Prospectus [Line Items]	rr_ProspectusLineItems
Maximum sales charge (load) imposed on purchases (as a percentage of offering price)	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	none
Maximum deferred sales charge (load) (as a percentage of original purchase price or redemption proceeds, whichever is lower)	rr_MaximumDeferredSalesChargeOverOther	none	[1]
Management fees	rr_ManagementFeesOverAssets	0.28%	[2]
Distribution and service (12b-1) fees	rr_DistributionAndService12b1FeesOverAssets	0.10%
Other expenses	rr_OtherExpensesOverAssets	0.10%
Total annual fund operating expenses	rr_ExpensesOverAssets	0.48%
Expense reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.08%)	[3]
Total annual fund operating expenses after expense reimbursement	rr_NetExpensesOverAssets	0.40%
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	$ 41
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	146
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	261
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	$ 596
Annual Return 2012	rr_AnnualReturn2012	0.94%
Annual Return 2013	rr_AnnualReturn2013	0.59%
Annual Return 2014	rr_AnnualReturn2014	0.51%
Annual Return 2015	rr_AnnualReturn2015	0.27%
Annual Return 2016	rr_AnnualReturn2016	0.98%
Annual Return 2017	rr_AnnualReturn2017	1.30%
Annual Return 2018	rr_AnnualReturn2018	1.83%
Label	rr_AverageAnnualReturnLabel	before taxes
1 Year	rr_AverageAnnualReturnYear01	1.83%
5 Years	rr_AverageAnnualReturnYear05	0.98%
Since Inception	rr_AverageAnnualReturnSinceInception	0.89%
Inception Date	rr_AverageAnnualReturnInceptionDate	Oct. 17, 2011
Putnam Ultra Short Duration Income Fund* | Class A | after taxes on distributions
Prospectus [Line Items]	rr_ProspectusLineItems
1 Year	rr_AverageAnnualReturnYear01	0.96%
5 Years	rr_AverageAnnualReturnYear05	0.55%
Since Inception	rr_AverageAnnualReturnSinceInception	0.53%
Inception Date	rr_AverageAnnualReturnInceptionDate	Oct. 17, 2011
Putnam Ultra Short Duration Income Fund* | Class A | after taxes on distributions and sale of fund shares
Prospectus [Line Items]	rr_ProspectusLineItems
1 Year	rr_AverageAnnualReturnYear01	1.07%
5 Years	rr_AverageAnnualReturnYear05	0.55%
Since Inception	rr_AverageAnnualReturnSinceInception	0.52%
Inception Date	rr_AverageAnnualReturnInceptionDate	Oct. 17, 2011
Putnam Ultra Short Duration Income Fund* | Class B
Prospectus [Line Items]	rr_ProspectusLineItems
Maximum sales charge (load) imposed on purchases (as a percentage of offering price)	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	none
Maximum deferred sales charge (load) (as a percentage of original purchase price or redemption proceeds, whichever is lower)	rr_MaximumDeferredSalesChargeOverOther	none	[4]
Management fees	rr_ManagementFeesOverAssets	0.28%	[2]
Distribution and service (12b-1) fees	rr_DistributionAndService12b1FeesOverAssets	0.50%
Other expenses	rr_OtherExpensesOverAssets	0.10%
Total annual fund operating expenses	rr_ExpensesOverAssets	0.88%
Expense reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.08%)	[3]
Total annual fund operating expenses after expense reimbursement	rr_NetExpensesOverAssets	0.80%
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	$ 582	[5]
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	573	[5]
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	680	[5]
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	962	[5]
Expense Example, No Redemption, 1 Year	rr_ExpenseExampleNoRedemptionYear01	82
Expense Example, No Redemption, 3 Years	rr_ExpenseExampleNoRedemptionYear03	273
Expense Example, No Redemption, 5 Years	rr_ExpenseExampleNoRedemptionYear05	480
Expense Example, No Redemption, 10 Years	rr_ExpenseExampleNoRedemptionYear10	$ 962
Label	rr_AverageAnnualReturnLabel	before taxes
1 Year	rr_AverageAnnualReturnYear01	1.43%
5 Years	rr_AverageAnnualReturnYear05	0.58%
Since Inception	rr_AverageAnnualReturnSinceInception	0.49%
Inception Date	rr_AverageAnnualReturnInceptionDate	Oct. 17, 2011
Putnam Ultra Short Duration Income Fund* | Class C
Prospectus [Line Items]	rr_ProspectusLineItems
Maximum sales charge (load) imposed on purchases (as a percentage of offering price)	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	none
Maximum deferred sales charge (load) (as a percentage of original purchase price or redemption proceeds, whichever is lower)	rr_MaximumDeferredSalesChargeOverOther	none	[6]
Management fees	rr_ManagementFeesOverAssets	0.28%	[2]
Distribution and service (12b-1) fees	rr_DistributionAndService12b1FeesOverAssets	0.50%
Other expenses	rr_OtherExpensesOverAssets	0.10%
Total annual fund operating expenses	rr_ExpensesOverAssets	0.88%
Expense reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.08%)	[3]
Total annual fund operating expenses after expense reimbursement	rr_NetExpensesOverAssets	0.80%
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	$ 182
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	273
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	480
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	$ 1,077
Label	rr_AverageAnnualReturnLabel	before taxes
1 Year	rr_AverageAnnualReturnYear01	1.43%
5 Years	rr_AverageAnnualReturnYear05	0.58%
Since Inception	rr_AverageAnnualReturnSinceInception	0.49%
Inception Date	rr_AverageAnnualReturnInceptionDate	Oct. 17, 2011
Putnam Ultra Short Duration Income Fund* | Class N
Prospectus [Line Items]	rr_ProspectusLineItems
Maximum sales charge (load) imposed on purchases (as a percentage of offering price)	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	1.50%
Maximum deferred sales charge (load) (as a percentage of original purchase price or redemption proceeds, whichever is lower)	rr_MaximumDeferredSalesChargeOverOther	0.25%	[7]
Management fees	rr_ManagementFeesOverAssets	0.28%	[2]
Distribution and service (12b-1) fees	rr_DistributionAndService12b1FeesOverAssets	0.25%
Other expenses	rr_OtherExpensesOverAssets	0.10%	[8]
Total annual fund operating expenses	rr_ExpensesOverAssets	0.63%
Expense reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.08%)	[3]
Total annual fund operating expenses after expense reimbursement	rr_NetExpensesOverAssets	0.55%
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	$ 205
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	341
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	488
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	$ 917
Label	rr_AverageAnnualReturnLabel	before taxes	[9]
1 Year	rr_AverageAnnualReturnYear01	0.25%	[9]
5 Years	rr_AverageAnnualReturnYear05	0.54%	[9]
Since Inception	rr_AverageAnnualReturnSinceInception	0.55%	[9]
Inception Date	rr_AverageAnnualReturnInceptionDate	Oct. 17, 2011	[9]
Putnam Ultra Short Duration Income Fund* | Class R
Prospectus [Line Items]	rr_ProspectusLineItems
Maximum sales charge (load) imposed on purchases (as a percentage of offering price)	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	none
Maximum deferred sales charge (load) (as a percentage of original purchase price or redemption proceeds, whichever is lower)	rr_MaximumDeferredSalesChargeOverOther	none
Management fees	rr_ManagementFeesOverAssets	0.28%	[2]
Distribution and service (12b-1) fees	rr_DistributionAndService12b1FeesOverAssets	0.50%
Other expenses	rr_OtherExpensesOverAssets	0.10%
Total annual fund operating expenses	rr_ExpensesOverAssets	0.88%
Expense reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.08%)	[3]
Total annual fund operating expenses after expense reimbursement	rr_NetExpensesOverAssets	0.80%
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	$ 82
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	273
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	480
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	$ 1,077
Label	rr_AverageAnnualReturnLabel	before taxes
1 Year	rr_AverageAnnualReturnYear01	1.43%
5 Years	rr_AverageAnnualReturnYear05	0.58%
Since Inception	rr_AverageAnnualReturnSinceInception	0.49%
Inception Date	rr_AverageAnnualReturnInceptionDate	Oct. 17, 2011
Putnam Ultra Short Duration Income Fund* | Class R6
Prospectus [Line Items]	rr_ProspectusLineItems
Maximum sales charge (load) imposed on purchases (as a percentage of offering price)	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	none
Maximum deferred sales charge (load) (as a percentage of original purchase price or redemption proceeds, whichever is lower)	rr_MaximumDeferredSalesChargeOverOther	none
Management fees	rr_ManagementFeesOverAssets	0.28%	[2]
Other expenses	rr_OtherExpensesOverAssets	0.09%
Total annual fund operating expenses	rr_ExpensesOverAssets	0.37%
Expense reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.08%)	[3]
Total annual fund operating expenses after expense reimbursement	rr_NetExpensesOverAssets	0.29%
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	$ 30
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	111
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	200
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	$ 460
Label	rr_AverageAnnualReturnLabel	before taxes	[10]
1 Year	rr_AverageAnnualReturnYear01	1.84%	[10]
5 Years	rr_AverageAnnualReturnYear05	1.06%	[10]
Since Inception	rr_AverageAnnualReturnSinceInception	1.01%	[10]
Inception Date	rr_AverageAnnualReturnInceptionDate	Oct. 17, 2011	[10]
Putnam Ultra Short Duration Income Fund* | Class Y
Prospectus [Line Items]	rr_ProspectusLineItems
Maximum sales charge (load) imposed on purchases (as a percentage of offering price)	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	none
Maximum deferred sales charge (load) (as a percentage of original purchase price or redemption proceeds, whichever is lower)	rr_MaximumDeferredSalesChargeOverOther	none
Management fees	rr_ManagementFeesOverAssets	0.28%	[2]
Other expenses	rr_OtherExpensesOverAssets	0.10%
Total annual fund operating expenses	rr_ExpensesOverAssets	0.38%
Expense reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.08%)	[3]
Total annual fund operating expenses after expense reimbursement	rr_NetExpensesOverAssets	0.30%
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	$ 31
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	114
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	205
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	$ 473
Label	rr_AverageAnnualReturnLabel	before taxes
1 Year	rr_AverageAnnualReturnYear01	1.93%
5 Years	rr_AverageAnnualReturnYear05	1.06%
Since Inception	rr_AverageAnnualReturnSinceInception	1.01%
Inception Date	rr_AverageAnnualReturnInceptionDate	Oct. 17, 2011
Putnam Short Term Investment Fund
Prospectus [Line Items]	rr_ProspectusLineItems
Risk/Return [Heading]	rr_RiskReturnHeading	Fund summary
Objective [Heading]	rr_ObjectiveHeading	Goal
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	Putnam Short Term Investment Fund seeks as high a rate of current income as Putnam Investment Management, LLC believes is consistent with preservation of capital and maintenance of liquidity.
Expense [Heading]	rr_ExpenseHeading	Fees and expenses
Expense Narrative [Text Block]	rr_ExpenseNarrativeTextBlock	The following tables describe the fees and expenses you may pay if you buy and hold shares of the fund.
Shareholder Fees Caption [Text]	rr_ShareholderFeesCaption	Shareholder fees (fees paid directly from your investment)
Operating Expenses Caption [Text]	rr_OperatingExpensesCaption	Annual fund operating expenses (expenses you pay each year as a percentage of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	November 30, 2020.
Portfolio Turnover [Heading]	rr_PortfolioTurnoverHeading	Portfolio turnover
Portfolio Turnover [Text Block]	rr_PortfolioTurnoverTextBlock	The fund pays transaction-related costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher turnover rate may indicate higher transaction costs and may result in higher taxes when the fund’s shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or the above example, affect fund performance. The fund’s turnover rate in the most recent fiscal year was 0%,
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	none
Expense Example [Heading]	rr_ExpenseExampleHeading	Example
Expense Example Narrative [Text Block]	rr_ExpenseExampleNarrativeTextBlock	The following hypothetical example is intended to help you compare the cost of investing in the fund with the cost of investing in other funds. It assumes that you invest $10,000 in the fund for the time periods indicated and then redeem or hold all your shares at the end of those periods. It assumes a 5% return on your investment each year and that the fund’s operating expenses remain the same. Only the first year of each period in the example takes into account the expense reimbursement described above. Your actual costs may be higher or lower.
Strategy [Heading]	rr_StrategyHeading	Investments, risks, and performance
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	Investments We invest in a diversified portfolio of fixed income securities comprised of short duration, investment-grade money market and other fixed income securities. The fund’s investments may include obligations of the U.S. government, its agencies and instrumentalities, which are backed by the full faith and credit of the United States (e.g., U.S. Treasury bonds and Ginnie Mae mortgage-backed bonds) or by only the credit of a federal agency or government-sponsored entity (e.g., Fannie Mae or Freddie Mac mortgage-backed bonds), domestic corporate debt obligations, municipal debt securities, securitized debt instruments (such as mortgage- and asset-backed securities), repurchase agreements, certificates of deposit, bankers acceptances, commercial paper (including asset-backed commercial paper), time deposits, Yankee Eurodollar securities and other money market instruments. We may also invest in U.S.dollar-denominated foreign securities of these types. Under normal circumstances, the effective duration of the fund’s portfolio will generally not be greater than one year. Effective duration provides a measure of a fund’s interest-rate sensitivity. The longer a fund’s duration, the more sensitive the fund is to shifts in interest rates. The fund will maintain a dollar-weighted average portfolio maturity of three years or less. We may consider, among other factors, credit, interest rate and prepayment risks, as well as general market conditions, when deciding whether to buy or sell investments. We may also use derivatives, such as futures, options and swap contracts, for both hedging and non-hedging purposes.
Risk [Heading]	rr_RiskHeading	Risks
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	It is important to understand that you can lose money by investing in the fund. The effects of inflation may erode the value of your investment over time. The value of investments in the fund’s portfolio may fall or fail to rise over extended periods of time for a variety of reasons, including general economic, political or financial market conditions, investor sentiment and market perceptions, government actions, geopolitical events or changes, and factors related to a specific issuer, geography, industry or sector. These and other factors may lead to increased volatility and reduced liquidity in the fund’s portfolio holdings. The risks associated with fixed income investments include interest rate risk, which means the value of the fund’s investments is likely to fall if interest rates rise. Fixed income investments are also subject to credit risk, which is the risk that the issuer of a fixed income investment may default on payment of interest or principal. Credit risk is generally greater for debt not backed by the full faith and credit of the U.S. government, and interest rate risk is generally greater for longer-term debt. Mortgage-backed investments, unlike traditional debt investments, are also subject to prepayment risk, which means that they may increase in value less than other bonds when interest rates decline and decline in value more than other bonds when interest rates rise. We may have to invest the proceeds from prepaid investments, including mortgage-backed investments, in other investments with less attractive terms and yields. Our use of derivatives may increase the risks of investing in the fund by increasing investment exposure (which may be considered leverage) or, in the case of many over-the-counter instruments, because of the potential inability to terminate or sell derivatives positions and the potential failure of the other party to the instrument to meet its obligations. The fund may not achieve its goal, and it is not intended to be a complete investment program. An investment in the fund is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Risk Lose Money [Text]	rr_RiskLoseMoney	It is important to understand that you can lose money by investing in the fund.
Risk Not Insured Depository Institution [Text]	rr_RiskNotInsuredDepositoryInstitution	An investment in the fund is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	Performance
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	The performance information below gives some indication of the risks associated with an investment in the fund by showing the fund’s performance year to year and over time. Please remember that past performance is not necessarily an indication of future results.
Performance Information Illustrates Variability of Returns [Text]	rr_PerformanceInformationIllustratesVariabilityOfReturns	The performance information below gives some indication of the risks associated with an investment in the fund by showing the fund’s performance year to year and over time.
Performance Availability Website Address [Text]	rr_PerformanceAvailabilityWebSiteAddress	putnam.com
Performance Past Does Not Indicate Future [Text]	rr_PerformancePastDoesNotIndicateFuture	Please remember that past performance is not necessarily an indication of future results.
Bar Chart [Heading]	rr_BarChartHeading	Annual total returns for class P shares
Bar Chart Does Not Reflect Sales Loads [Text]	rr_BarChartDoesNotReflectSalesLoads	The bar chart does not reflect the impact of sales charges. If it did, performance would be lower.
Bar Chart Closing [Text Block]	rr_BarChartClosingTextBlock	Year-to-date performance through 9/30/19  1.89% Best calendar quarter Q4 2018   0.60% Worst calendar quarter Q3 2014 0.01%
Year to Date Return, Label	rr_YearToDateReturnLabel	Year-to-date performance
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Sep. 30, 2019
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	1.89%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	Best calendar quarter
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Dec. 31, 2018
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	0.60%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	Worst calendar quarter
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Sep. 30, 2014
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	0.01%
Performance Table Heading	rr_PerformanceTableHeading	Average annual total returns (for periods ended 12/31/18)
Performance Table Uses Highest Federal Rate	rr_PerformanceTableUsesHighestFederalRate	After-tax returns reflect the historical highest individual federal marginal income tax rates and do not reflect state and local taxes.
Performance Table Not Relevant to Tax Deferred	rr_PerformanceTableNotRelevantToTaxDeferred	Actual after-tax returns depend on an investor's tax situation and may differ from those shown.
Performance Table Closing [Text Block]	rr_PerformanceTableClosingTextBlock	ICE BofAML Indexes: ICE Data Indices, LLC (“ICE BofAML”), used with permission. ICE BofAML permits use of the ICE BofAML indices and related data on an “as is” basis; makes no warranties regarding same; does not guarantee the suitability, quality, accuracy, timeliness, and/or completeness of the ICE BofAML indices or any data included in, related to, or derived therefrom; assumes no liability in connection with the use of the foregoing; and does not sponsor, endorse, or recommend Putnam Investments, or any of its products or services. After-tax returns reflect the historical highest individual federal marginal income tax rates and do not reflect state and local taxes. Actual after-tax returns depend on an investor’s tax situation and may differ from those shown.
Putnam Short Term Investment Fund | ICE BofAML U.S. Treasury Bill Index (no deduction for fees, expenses or taxes)
Prospectus [Line Items]	rr_ProspectusLineItems
1 Year	rr_AverageAnnualReturnYear01	1.88%
5 Years	rr_AverageAnnualReturnYear05	0.64%
Since Inception	rr_AverageAnnualReturnSinceInception	0.56%
Inception Date	rr_AverageAnnualReturnInceptionDate	Feb. 19, 2013
Putnam Short Term Investment Fund | Class P
Prospectus [Line Items]	rr_ProspectusLineItems
Maximum sales charge (load) imposed on purchases (as a percentage of offering price)	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	none
Maximum deferred sales charge (load) (as a percentage of original purchase price or redemption proceeds, whichever is lower)	rr_MaximumDeferredSalesChargeOverOther	none
Management fees	rr_ManagementFeesOverAssets	0.25%
Distribution and service (12b-1) fees	rr_DistributionAndService12b1FeesOverAssets
Other expenses	rr_OtherExpensesOverAssets	0.03%
Total annual fund operating expenses	rr_ExpensesOverAssets	0.28%
Expense reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.25%)	[3]
Total annual fund operating expenses after expense reimbursement	rr_NetExpensesOverAssets	0.03%
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	$ 3
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	65
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	132
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	$ 331
Annual Return 2014	rr_AnnualReturn2014	0.07%
Annual Return 2015	rr_AnnualReturn2015	0.12%
Annual Return 2016	rr_AnnualReturn2016	0.46%
Annual Return 2017	rr_AnnualReturn2017	1.02%
Annual Return 2018	rr_AnnualReturn2018	2.02%
Label	rr_AverageAnnualReturnLabel	before taxes
1 Year	rr_AverageAnnualReturnYear01	2.02%
5 Years	rr_AverageAnnualReturnYear05	0.74%
Since Inception	rr_AverageAnnualReturnSinceInception	0.64%
Inception Date	rr_AverageAnnualReturnInceptionDate	Feb. 19, 2013
Putnam Short Term Investment Fund | Class P | after taxes on distributions
Prospectus [Line Items]	rr_ProspectusLineItems
1 Year	rr_AverageAnnualReturnYear01	1.19%
5 Years	rr_AverageAnnualReturnYear05	0.43%
Since Inception	rr_AverageAnnualReturnSinceInception	0.37%
Inception Date	rr_AverageAnnualReturnInceptionDate	Feb. 19, 2013
Putnam Short Term Investment Fund | Class P | after taxes on distributions and sale of fund shares
Prospectus [Line Items]	rr_ProspectusLineItems
1 Year	rr_AverageAnnualReturnYear01	1.19%
5 Years	rr_AverageAnnualReturnYear05	0.43%
Since Inception	rr_AverageAnnualReturnSinceInception	0.37%
Inception Date	rr_AverageAnnualReturnInceptionDate	Feb. 19, 2013

[1] Class A shares purchased directly from the fund are not subject to any contingent deferred sales charge (CDSC). However, class A shares of the fund that were obtained in exchange for class A shares of another Putnam Fund that were subject to a CDSC of 1.00% at the time of exchange may be subject to a CDSC unless the one-year CDSC period has expired or a CDSC waiver applies.

[2] Restated to reflect current fees.

[3] Reflects Putnam Investment Management, LLC's contractual obligation to waive its management fee for this fund through at least November 30, 2020. This obligation may be modified or discontinued only with approval of the Board of Trustees.

[4] Class B shares purchased directly from the fund are not subject to any CDSC. However, class B shares of the fund that were obtained in exchange for class B shares of another Putnam Fund that were subject to a CDSC of up to 5.00% at the time of exchange may be subject to a CDSC unless the prescribed time period has expired or a CDSC waiver applies.

[5] Reflects assessment of deferred sales charge assuming class B shares were acquired by exchange from one or more other Putnam funds immediately after purchase of shares from such other fund(s)

[6] Class C shares purchased directly from the fund are not subject to any CDSC. However, class C shares of the fund that were obtained in exchange for class C shares of another Putnam Fund that were subject to a CDSC of 1.00% at the time of exchange may be subject to a CDSC unless the one-year CDSC period has expired or a CDSC waiver applies.

[7] Applies only to certain redemptions of shares bought with no initial sales charge.

[8] Annualized.

[9] Performance for class N shares prior to their inception (11/1/18) is derived from the historical performance of class A shares, adjusted for the sales charge and higher 12b-1 fees currently applicable to class N shares.

[10] Performance for class R6 shares prior to their inception (7/2/12) is derived from the historical performance of class Y shares and has not been adjusted for the lower investor servicing fees applicable to class R6 shares; had it, returns would have been higher.