XML 41 R29.htm IDEA: XBRL DOCUMENT
v3.21.2

Goodwill and Identifiable Assets (Acquired Intangible Assets) (Details) - USD ($) $ in Millions | 9 Months Ended |
--- | --- | ---
Sep. 30, 2021 | Dec. 31, 2020
Intangible assets subject to amortization: |  |
Gross Carrying Amount | $ 609.8 | $ 529.8
Accumulated Amortization | 342.5 | 302.5
Net Carrying Amount | 267.3 | 227.3
Intangible assets not subject to amortization: |  |
Trademarks, Carrying Amount | 242.6 | 242.6
Intangible Assets, Gross (Excluding Goodwill) | 852.4 | 772.4
Intangible Assets, Net (Excluding Goodwill), Total | 509.9 | 469.9
Customer and Contractual Relationships |  |
Intangible assets subject to amortization: |  |
Accumulated Amortization | 246.5 | 211.3
Net Carrying Amount | 252.5 | 216.7
Total |  |
Other Finite-Lived Intangible Assets, Gross | $ 499.0 | 428.0
Customer and Contractual Relationships | Minimum [Member] |  |
Intangible Assets [Line Items] |  |
Finite-Lived Intangible Asset, Useful Life | 7 years |
Customer and Contractual Relationships | Maximum [Member] |  |
Intangible Assets [Line Items] |  |
Finite-Lived Intangible Asset, Useful Life | 13 years |
Contractor Relations |  |
Intangible Assets [Line Items] |  |
Finite-Lived Intangible Asset, Useful Life | 4 years |
Intangible assets subject to amortization: |  |
Accumulated Amortization | $ 45.5 | 45.3
Net Carrying Amount | 0.0 | 0.2
Total |  |
Other Finite-Lived Intangible Assets, Gross | 45.5 | 45.5
Backlog |  |
Intangible assets subject to amortization: |  |
Accumulated Amortization | 29.9 | 28.5
Net Carrying Amount | 5.5 | 0.8
Total |  |
Other Finite-Lived Intangible Assets, Gross | $ 35.4 | 29.3
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: |  |
Accumulated Amortization | $ 20.6 | 17.4
Net Carrying Amount | 9.3 | 9.6
Total |  |
Other Finite-Lived Intangible Assets, Gross | $ 29.9 | $ 27.0
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 Intangible Assets, Net [Abstract] + References No definition available. + Details
Name: | asgn_IntangibleAssetsNetAbstract
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: | duration

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 -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 30 -Section 50 -Paragraph 2 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275 + Details
Name: | us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount before 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 -Publisher FASB -Name Accounting Standards Codification -Topic 928 -SubTopic 340 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6473545&loc=d3e61844-108004 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 30 -Section 50 -Paragraph 2 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275 + Details
Name: | us-gaap_FiniteLivedIntangibleAssetsGross
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
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 -Publisher FASB -Name Accounting Standards Codification -Topic 926 -SubTopic 20 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=120154696&loc=d3e54445-107959 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 30 -Section 50 -Paragraph 2 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275 + 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 -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 30 -Section 50 -Paragraph 2 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275 + 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 No definition available. + 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 -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 30 -Section 50 -Paragraph 2 -Subparagraph ((a)(1),(b)) -URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 30 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6388964&loc=d3e16212-109274 + 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 -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 30 -Section 50 -Paragraph 2 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275 + 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=asgn_ContractorRelationsMember
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: |