Face (par) amount of debt instrument at time of issuance.

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- Definition

Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

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Contractual interest rate for funds borrowed, under the debt agreement.

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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.

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Amount, after accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

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Including the current and noncurrent portions, carrying value as of the balance sheet date of long-term debt (with maturities initially due after one year or beyond the operating cycle if longer) identified as Junior Subordinated Notes, which have a lower priority than senior instruments.

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Including the current and noncurrent portions, carrying value as of the balance sheet date of Notes with the highest claim on the assets of the issuer in case of bankruptcy or liquidation (with maturities initially due after one year or beyond the operating cycle if longer). Senior note holders are paid off in full before any payments are made to junior note holders.

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Debt - Outstanding Debt (Details) - USD ($) $ in Millions	Sep. 30, 2021	Sep. 15, 2021	Aug. 12, 2021	Mar. 15, 2021	Oct. 19, 2020	Sep. 30, 2020	Jul. 31, 2020
Debt Instrument [Line Items]
Total	$ 3,399.4					$ 3,017.1	$ 2,000.0
Debt issuance costs	(12.6)					(2.1)
Franklin Resources, Inc. [Member]
Debt Instrument [Line Items]
Senior notes	1,893.7					699.5
Legg Mason [Member]
Debt Instrument [Line Items]
Total	1,518.3					2,319.7
Notes Due September 2022 [Member] \| Franklin Resources, Inc. [Member]
Debt Instrument [Line Items]
Senior notes	$ 299.9					$ 299.8
Effective Interest Rate	2.93%					2.93%
Debt Face Amount	$ 300.0
Stated Interest Rate	2.80%
Notes Due March 2025 [Member] \| Franklin Resources, Inc. [Member]
Debt Instrument [Line Items]
Senior notes	$ 399.7					$ 399.7
Effective Interest Rate	2.97%					2.97%
Debt Face Amount	$ 400.0
Stated Interest Rate	2.85%
Notes Due October 2030 [Member]
Debt Instrument [Line Items]
Debt issuance costs			$ (7.7)
Debt Face Amount			$ 100.0		$ 750.0
Stated Interest Rate			1.60%		1.60%
Notes Due October 2030 [Member] \| Franklin Resources, Inc. [Member]
Debt Instrument [Line Items]
Senior notes	$ 846.3					$ 0.0
Effective Interest Rate	1.74%
Debt Face Amount	$ 850.0
Stated Interest Rate	1.60%
Notes Due August 2051 [Member]
Debt Instrument [Line Items]
Debt issuance costs			$ (4.1)
Debt Face Amount			$ 350.0
Stated Interest Rate			2.95%
Notes Due August 2051 [Member] \| Franklin Resources, Inc. [Member]
Debt Instrument [Line Items]
Senior notes	$ 347.8					0.0
Effective Interest Rate	3.00%
Debt Face Amount	$ 350.0
Stated Interest Rate	2.95%
Notes Due July 2024 [Member] \| Legg Mason [Member]
Debt Instrument [Line Items]
Senior notes	$ 266.5					$ 272.4
Effective Interest Rate	1.53%					1.53%
Debt Face Amount	$ 250.0
Stated Interest Rate	3.95%
Notes Due March 2026 [Member] \| Legg Mason [Member]
Debt Instrument [Line Items]
Senior notes	$ 509.6					$ 523.0
Effective Interest Rate	1.80%					1.80%
Debt Face Amount	$ 450.0
Stated Interest Rate	4.75%
Notes Due January 2044 [Member] \| Legg Mason [Member]
Debt Instrument [Line Items]
Senior notes	$ 742.2					$ 747.5
Effective Interest Rate	3.38%					3.38%
Debt Face Amount	$ 550.0
Stated Interest Rate	5.625%
Notes Due March 2056 [Member]
Debt Instrument [Line Items]
Debt Face Amount				$ 250.0
Stated Interest Rate				6.375%
Notes Due March 2056 [Member] \| Legg Mason [Member]
Debt Instrument [Line Items]
Junior Subordinated Notes	$ 0.0					$ 260.7
Effective Interest Rate						6.08%
Debt Face Amount						$ 250.0
Stated Interest Rate						6.375%
Notes Due September 2056 [Member]
Debt Instrument [Line Items]
Debt Face Amount		$ 500.0
Stated Interest Rate		5.45%
Notes Due September 2056 [Member] \| Legg Mason [Member]
Debt Instrument [Line Items]
Junior Subordinated Notes	$ 0.0					$ 516.1
Effective Interest Rate						5.25%
Debt Face Amount						$ 500.0
Stated Interest Rate						5.45%