Income Tax Disclosure [Line Items]

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- Definition

Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32687-109319

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- Definition

Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
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- Definition

The portion of earnings or loss from continuing operations before income taxes that is attributable to foreign operations, which is defined as Income or Loss generated from operations located outside the entity's country of domicile.

+ References

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- Definition

The parent entity's interest in net assets of the subsidiary, expressed as a percentage.

+ References

No definition available.

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- Definition

Amount of income tax expense (benefit) for remeasurement of deferred tax from change in tax rate pursuant to Tax Cuts and Jobs Act.

+ References

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-Publisher FASB
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- Definition

Amount of income tax expense from transition tax on accumulated earnings of controlled foreign corporation deemed repatriated pursuant to Tax Cuts and Jobs Act.

+ References

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- Definition

Amount of undistributed earnings of foreign subsidiaries intended to be permanently reinvested outside the country of domicile.

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Income Taxes (Details) - USD ($) $ in Millions		12 Months Ended
Income Taxes (Details) - USD ($) $ in Millions	Dec. 22, 2017	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018	Oct. 21, 2019
Income Tax Disclosure
Effective income tax rate		8.40%	24.20%	19.80%
Effective income tax rate reconciliation, at federal statutory income tax rate, percentage	35.00%	21.00%	21.00%	24.50%
Undistributed earnings of foreign subsidiaries		$ 2.3	$ 2.9
Income (loss) from continuing operations before income taxes, foreign		$ (0.8)	$ 1.0	$ 1.0
Tax Cuts and Jobs Act, change in tax rate, income tax expense (benefit)				9.9
Tax Cuts and Jobs Act, transition tax for accumulated foreign earnings, income tax expense				$ 0.5
BellRing Brands, LLC unit \| BellRing Brands, Inc.
Income Tax Disclosure
Noncontrolling interest, ownership percentage by parent		28.80%			28.80%