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Goodwill and Identifiable Assets Goodwill (Details) - USD ($) $ in Millions | 3 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2024 | Mar. 31, 2023 | Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2022
Goodwill [Roll Forward] |  |  |  |  |
Gross goodwill, period start | $ 1,894.1 | $ 1,891.9 | $ 1,894.1 | $ 1,891.9 |
Purchase price adjustment |  |  |  | 1.1 |
Translation adjustment | 1.1 |  | (1.0) |  |
Gross goodwill, period end |  |  | 1,893.1 | 1,894.1 | $ 1,891.9
Amortization of intangible assets |  |  | 58.1 | 71.7 | 65.1
Commercial Business |  |  |  |  |
Goodwill [Roll Forward] |  |  |  |  |
Gross goodwill, period start | 1,075.8 | 1,074.7 | 1,075.8 | 1,074.7 |
Purchase price adjustment |  |  |  | 0.0 |
Translation adjustment |  | 1.1 | (1.0) |  |
Gross goodwill, period end |  |  | 1,074.8 | 1,075.8 | 1,074.7
Federal Government Business |  |  |  |  |
Goodwill [Roll Forward] |  |  |  |  |
Gross goodwill, period start | $ 818.3 | 817.2 | 818.3 | 817.2 |
Purchase price adjustment |  | 1.1 |  |  |
Translation adjustment |  | $ 0.0 | 0.0 |  |
Gross goodwill, period end |  |  | $ 818.3 | $ 818.3 | $ 817.2

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- Definition The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Section 45 -Paragraph 28 -Subparagraph (b) -SubTopic 10 -Topic 230 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482740/230-10-45-28 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Topic 350 -SubTopic 30 -Name Accounting Standards Codification -Section 55 -Paragraph 40 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482640/350-30-55-40 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 350 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (a)(2) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482665/350-30-50-2 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 350 -SubTopic 30 -Name Accounting Standards Codification -Section 45 -Paragraph 2 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482686/350-30-45-2 + Details
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- Definition Amount of foreign currency translation gain (loss) which increases (decreases) asset representing future economic benefit from other asset acquired in business combination or from joint venture formation or both, that is 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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