XML 58 R33.htm IDEA: XBRL DOCUMENT
v3.20.1

Goodwill and Identifiable Assets (Goodwill) (Details) - USD ($) $ in Millions |  | 3 Months Ended | 12 Months Ended |
--- | --- | --- | --- | ---
Jan. 24, 2020 | Mar. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Goodwill [Roll Forward] |  |  |  |
Gross goodwill |  | $ 1,547.0 | $ 1,486.9 | $ 1,421.1
Translation adjustment |  | (1.0) | (0.3) |
Apex |  |  |  |
Goodwill [Roll Forward] |  |  |  |
Gross goodwill |  | 703.2 | 703.5 | 662.1
Translation adjustment |  | (0.3) |  |
Oxford |  |  |  |
Goodwill [Roll Forward] |  |  |  |
Gross goodwill |  | 229.8 | 230.5 | 230.8
Translation adjustment |  | (0.7) | (0.3) |
ECS |  |  |  |
Goodwill [Roll Forward] |  |  |  |
Gross goodwill |  | 614.0 | 552.9 | $ 528.2
DHA |  |  |  |
Goodwill [Roll Forward] |  |  |  |
Goodwill, Acquired During Period |  |  | 24.7 |
Intersys |  |  |  |
Goodwill [Roll Forward] |  |  |  |
Goodwill, Acquired During Period |  |  | $ 41.4 |
BlackStone Federal |  |  |  |
Goodwill [Roll Forward] |  |  |  |
Goodwill, Acquired During Period | $ 61.1 | $ 61.1 |  |

X
- 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://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=108376223&loc=d3e13816-109267 + Details
Name: | us-gaap_GoodwillAcquiredDuringPeriod
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- 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://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (f) -URI http://asc.fasb.org/extlink&oid=108376223&loc=d3e13816-109267 + Details
Name: | us-gaap_GoodwillForeignCurrencyTranslationGainLoss
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- 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/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=108376223&loc=d3e13816-109267 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h) -URI http://asc.fasb.org/extlink&oid=108376223&loc=d3e13816-109267 + Details
Name: | us-gaap_GoodwillGross
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period. + References No definition available. + Details
Name: | us-gaap_GoodwillRollForward
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=asgn_ApexSegmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=asgn_OxfordSegmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=asgn_ECSMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_BusinessAcquisitionAxis=asgn_DHAMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_BusinessAcquisitionAxis=asgn_IntersysMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_BusinessAcquisitionAxis=asgn_BlackStoneFederalMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |