Amount of expenses for special or contractual termination benefits provided to current employees involuntarily terminated under a benefit arrangement associated exit or disposal activities pursuant to an authorized plan. Excludes expenses related to one-time termination benefits, a discontinued operation or an asset retirement obligation.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 420
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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-Section 50
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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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Name:	us-gaap_SeveranceCosts1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Restructuring Charges, Net of Reversals and Impairment, and Related Charges (Narratives) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Jun. 30, 2021
Restructuring Cost And Reserve [Line Items]
Restructuring charges, net of reversals and impairment	$ 1.0
Facility related charges	0.3
Severance and benefits charges	$ 0.7
Reduction-in-force
Restructuring Cost And Reserve [Line Items]
Reduction in force or severance and benefits			$ 8.8
Reduction-in-force \| Scenario Forecast
Restructuring Cost And Reserve [Line Items]
Reduction in force or severance and benefits				$ 1.0
Prior year Reduction-in-force plans
Restructuring Cost And Reserve [Line Items]
Restructuring charges, net of reversals and impairment		$ 6.1
Severance and benefits charges		2.2
Prior year Reduction-in-force plans \| Non-Cancelable Lease Payments
Restructuring Cost And Reserve [Line Items]
Charges for impairment of right-of-use assets		$ 3.9