XML 33 R22.htm IDEA: XBRL DOCUMENT
v3.23.3

Goodwill and Identifiable Assets (Acquired Intangible Assets) (Details) - USD ($) $ in Millions | Sep. 30, 2023 | Dec. 31, 2022
--- | --- | ---
Intangible assets subject to amortization: |  |
Other Finite-Lived Intangible Assets, Gross | $ 674.6 | $ 674.6
Accumulated Amortization | 431.7 | 377.8
Net Carrying Amount | 242.9 | 296.8
Intangible assets not subject to amortization: |  |
Trademarks, Carrying Amount | 272.8 | 272.8
Intangible Assets, Gross (Excluding Goodwill) | 947.4 | 947.4
Intangible Assets, Net (Excluding Goodwill), Total | 515.7 | 569.6
Customer and Contractual Relationships |  |
Intangible assets subject to amortization: |  |
Other Finite-Lived Intangible Assets, Gross | 589.3 | 589.3
Accumulated Amortization | 360.4 | 315.7
Net Carrying Amount | $ 228.9 | 273.6
Customer and Contractual Relationships | Minimum [Member] |  |
Intangible Assets [Line Items] |  |
Finite-Lived Intangible Asset, Useful Life | 1 year |
Customer and Contractual Relationships | Maximum [Member] |  |
Intangible Assets [Line Items] |  |
Finite-Lived Intangible Asset, Useful Life | 13 years |
Backlog |  |
Intangible assets subject to amortization: |  |
Other Finite-Lived Intangible Assets, Gross | $ 44.1 | 44.1
Accumulated Amortization | 42.2 | 36.5
Net Carrying Amount | $ 1.9 | 7.6
Backlog | Minimum [Member] |  |
Intangible Assets [Line Items] |  |
Finite-Lived Intangible Asset, Useful Life | 1 year |
Backlog | Maximum [Member] |  |
Intangible Assets [Line Items] |  |
Finite-Lived Intangible Asset, Useful Life | 3 years |
Noncompete Agreements |  |
Intangible assets subject to amortization: |  |
Other Finite-Lived Intangible Assets, Gross | $ 41.2 | 41.2
Accumulated Amortization | 29.1 | 25.6
Net Carrying Amount | $ 12.1 | $ 15.6
Noncompete Agreements | Minimum [Member] |  |
Intangible Assets [Line Items] |  |
Finite-Lived Intangible Asset, Useful Life | 1 year |
Noncompete Agreements | Maximum [Member] |  |
Intangible Assets [Line Items] |  |
Finite-Lived Intangible Asset, Useful Life | 7 years |

X
- Definition Intangible Assets [Line Items] + References No definition available. + Details
Name: | asgn_IntangibleAssetsLineItems
Namespace Prefix: | asgn_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Useful life of finite-lived intangible assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References No definition available. + Details
Name: | us-gaap_FiniteLivedIntangibleAssetUsefulLife
Namespace Prefix: | us-gaap_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | instant

X
- Definition Accumulated amount of amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 210 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(16)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480566/210-10-S99-1 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 350 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (a)(1) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482665/350-30-50-2 + Details
Name: | us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount after amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 926 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 5 -Publisher FASB -URI https://asc.fasb.org//1943274/2147483154/926-20-50-5 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 350 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (a)(1) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482665/350-30-50-2 + Details
Name: | us-gaap_FiniteLivedIntangibleAssetsNet
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- References No definition available. + Details
Name: | us-gaap_FiniteLivedIntangibleAssetsNetAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Carrying amount (original costs adjusted for previously recognized amortization and impairment) as of the balance sheet date for the rights acquired through registration of a trademark to gain or protect exclusive use of a business name, symbol or other device or style for a projected indefinite period of benefit. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 350 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482665/350-30-50-2 + Details
Name: | us-gaap_IndefiniteLivedTrademarks
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount before accumulated amortization of intangible assets, excluding goodwill. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 210 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(15)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480566/210-10-S99-1 + Details
Name: | us-gaap_IntangibleAssetsGrossExcludingGoodwill
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Sum of the carrying amounts of all intangible assets, excluding goodwill, as of the balance sheet date, net of accumulated amortization and impairment charges. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 350 -SubTopic 30 -Section 50 -Paragraph 2 -Subparagraph ((a)(1),(b)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482665/350-30-50-2 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 350 -SubTopic 30 -Section 45 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org//1943274/2147482686/350-30-45-1 + Details
Name: | us-gaap_IntangibleAssetsNetExcludingGoodwill
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- References No definition available. + Details
Name: | us-gaap_IntangibleAssetsNetIncludingGoodwillAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount before accumulated amortization of finite-lived intangible assets classified as other. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 350 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (a)(1) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482665/350-30-50-2 + Details
Name: | us-gaap_OtherFiniteLivedIntangibleAssetsGross
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Details
Name: | us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis=us-gaap_CustomerRelationshipsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_RangeAxis=srt_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_RangeAxis=srt_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis=us-gaap_OrderOrProductionBacklogMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis=us-gaap_NoncompeteAgreementsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |