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Goodwill and Identifiable Assets Goodwill (Details) - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2023 | Dec. 31, 2022
Goodwill [Roll Forward] |  |
Gross goodwill, period start | $ 1,891.9 | $ 1,569.5
Purchase price adjustment | 1.1 | (8.1)
Translation adjustment | 1.1 | (1.4)
Gross goodwill, period end | 1,894.1 | 1,891.9
Commercial Business |  |
Goodwill [Roll Forward] |  |
Gross goodwill, period start | 1,074.7 | 829.3
Purchase price adjustment | 0.0 | 0.4
Translation adjustment | 1.1 | (1.4)
Gross goodwill, period end | 1,075.8 | 1,074.7
Federal Government Business |  |
Goodwill [Roll Forward] |  |
Gross goodwill, period start | 817.2 | 740.2
Purchase price adjustment | 1.1 | (8.5)
Translation adjustment | 0.0 | 0.0
Gross goodwill, period end | 818.3 | 817.2
2022 Acquisitions |  |
Goodwill [Roll Forward] |  |
Acquisitions |  | 331.9
Goodwill, expected tax deductible amount | $ 250.7 |
2022 Acquisitions | Commercial Business |  |
Goodwill [Roll Forward] |  |
Acquisitions |  | 246.4
2022 Acquisitions | Federal Government Business |  |
Goodwill [Roll Forward] |  |
Acquisitions |  | $ 85.5

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- Definition The amount of goodwill arising from a business combination that is expected to be deductible for tax purposes. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 50 -Paragraph 1 -Subparagraph (d) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479581/805-30-50-1 + Details
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- Definition Amount of increase in asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized resulting from a business combination. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 350 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 24 -Publisher FASB -URI https://asc.fasb.org//1943274/2147482548/350-20-55-24 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 350 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482573/350-20-50-1 + Details
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- Definition Amount of foreign currency translation gain (loss) which increases (decreases) an asset representing future economic benefits from other assets acquired in a business combination that are not individually identified and separately recognized. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 350 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (f) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482573/350-20-50-1 + Details
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- Definition Amount before 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. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 350 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 24 -Publisher FASB -URI https://asc.fasb.org//1943274/2147482548/350-20-55-24 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 350 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482573/350-20-50-1 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 350 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (h) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482573/350-20-50-1 + Details
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- Definition Amount of increase (decrease) from adjustments after acquisition date under purchase accounting of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 350 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (g) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482573/350-20-50-1 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Section 25 -Paragraph 16 -SubTopic 10 -Topic 805 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479405/805-10-25-16 + Details
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