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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 |  |

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- Definition Discloses the amount charged against the accrued restructuring reserves, or earnings if not previously accrued, during the period for the specified type of restructuring cost. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 420 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (b)(1) -URI http://asc.fasb.org/extlink&oid=6394359&loc=d3e17939-110869 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 420 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SAB Topic 5.P.4(b)(1)) -URI http://asc.fasb.org/extlink&oid=115931487&loc=d3e140904-122747 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 420 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=6394359&loc=d3e17939-110869 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 420 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SAB Topic 5.P.4(d)) -URI http://asc.fasb.org/extlink&oid=115931487&loc=d3e140904-122747 + Details
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