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

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- Definition

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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No definition available.

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Amount, after accumulated amortization, of debt discount.

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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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Amount of interest payable on debt, including, but not limited to, trade payables.

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Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

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Including the current and noncurrent portions, carrying value as of the balance sheet date of uncollateralized debt obligations (with maturities initially due after one year or beyond the operating cycle if longer).

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Debt - Narrative (Details) - USD ($) $ in Millions	Sep. 30, 2021	Sep. 15, 2021	Aug. 12, 2021	Mar. 15, 2021	Oct. 19, 2020	Sep. 30, 2020
Debt Instrument [Line Items]
Debt Issuance Costs	$ 12.6					$ 2.1
Franklin Resources, Inc. [Member]
Debt Instrument [Line Items]
Unsecure debt	1,900.0
Legg Mason [Member]
Debt Instrument [Line Items]
Unsecure debt	1,250.0
Notes Due September 2056 [Member]
Debt Instrument [Line Items]
Debt Face Amount		$ 500.0
Stated Interest Rate		5.45%
Interest Payable		$ 6.8
Notes Due September 2056 [Member] \| Legg Mason [Member]
Debt Instrument [Line Items]
Debt Face Amount						$ 500.0
Stated Interest Rate						5.45%
Notes Due August 2051 [Member]
Debt Instrument [Line Items]
Debt Face Amount			$ 350.0
Stated Interest Rate			2.95%
Debt Issuance Costs			$ 4.1
Debt Instrument, Unamortized Discount			2.2
Notes Due August 2051 [Member] \| Franklin Resources, Inc. [Member]
Debt Instrument [Line Items]
Debt Face Amount	$ 350.0
Stated Interest Rate	2.95%
Notes Due March 2056 [Member]
Debt Instrument [Line Items]
Debt Face Amount				$ 250.0
Stated Interest Rate				6.375%
Interest Payable				$ 4.0
Notes Due March 2056 [Member] \| Legg Mason [Member]
Debt Instrument [Line Items]
Debt Face Amount						$ 250.0
Stated Interest Rate						6.375%
Notes Due October 2030 [Member]
Debt Instrument [Line Items]
Debt Face Amount			$ 100.0		$ 750.0
Stated Interest Rate			1.60%		1.60%
Debt Issuance Costs			$ 7.7
Debt Instrument, Unamortized Discount			$ 3.9
Notes Due October 2030 [Member] \| Franklin Resources, Inc. [Member]
Debt Instrument [Line Items]
Debt Face Amount	$ 850.0
Stated Interest Rate	1.60%
Commercial Paper [Member]
Debt Instrument [Line Items]
Line of credit Facility, maximum Borrowing capacity	$ 500.0