Weighted average amortization period of finite-lived intangible assets acquired either individually or as part of a group of assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Amount of consideration transferred, consisting of acquisition-date fair value of assets transferred by the acquirer, liabilities incurred by the acquirer, and equity interest issued by the acquirer.

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Amount due from customers or clients for goods or services, including trade receivables, that have been delivered or sold in the normal course of business, and amounts due from others, including related parties expected to be converted to cash, sold or exchanged within one year or the normal operating cycle, if longer, acquired at the acquisition date.

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Amount of other liabilities due within one year or within the normal operating cycle, if longer, assumed at the acquisition date.

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Amount of intangible assets, excluding goodwill, acquired at the acquisition date.

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The amount of property, plant, and equipment recognized as of the acquisition date.

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Amount recognized for assets, including goodwill, in excess of (less than) the aggregate liabilities assumed.

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Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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Acquisitions GloFish (Details) - USD ($) $ in Millions	12 Months Ended
Acquisitions GloFish (Details) - USD ($) $ in Millions	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Business Acquisition [Line Items]
Goodwill (Note 12)	$ 2,277.1	$ 2,133.3	$ 2,138.9
GloFish [Member]
Business Acquisition [Line Items]
Business Combination, Consideration Transferred	49.7
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Receivables	0.4
Property, plant and equipment	0.6
Goodwill (Note 12)	11.2
Goodwill (Note 12)	37.8
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Accounts Payable	0.3
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net	49.7
Tradenames Trademarks And Patents [Member] \| GloFish [Member]
Business Acquisition [Line Items]
Goodwill (Note 12)	$ 6.1
Technology-Based Intangible Assets [Member] \| GloFish [Member]
Business Acquisition [Line Items]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	13 years
Goodwill (Note 12)	$ 30.2
Customer Relationships [Member] \| GloFish [Member]
Business Acquisition [Line Items]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	10 years
Goodwill (Note 12)	$ 1.5