Contractual Quarterly Payments

No definition available.

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Namespace Prefix:	asgn_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The leverage ratio as defined in the credit agreement.

+ References

No definition available.

+ Details

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Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

- Definition

Leverage ratio limit in latest year of debt facility, as described in debt agreement.

+ References

No definition available.

+ Details

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Data Type:	xbrli:pureItemType
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Period Type:	instant

- Definition

Payments on Debt

+ References

No definition available.

+ Details

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Namespace Prefix:	asgn_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
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Balance Type:	na
Period Type:	duration

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 55

-Paragraph 8

-URI http://asc.fasb.org/extlink&oid=34725769&loc=d3e28878-108400

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 45

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28551-108399

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Weighted average interest rate of debt outstanding.

+ References

No definition available.

+ Details

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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.19(b),22(b))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The fee, expressed as a percentage of the line of credit facility, for available but unused credit capacity under the credit facility.

+ References

No definition available.

+ Details

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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The remaining balance of debt issuance expenses that were capitalized and are being amortized against income over the lives of the respective bond issues. This does not include the amounts capitalized as part of the cost of the utility plant or asset.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.17)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

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- Details

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- Details

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- Details

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- Details

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Period Type:

- Details

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- Details

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- Details

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Long-Term Debt Long-term Debt text (Details) $ in Thousands	1 Months Ended	9 Months Ended
Long-Term Debt Long-term Debt text (Details) $ in Thousands	Jun. 15, 2015 Rate	Sep. 30, 2015 USD ($)	Jun. 30, 2015	Jun. 05, 2015 USD ($)	Dec. 31, 2014 USD ($)
Debt Instrument [Line Items]
Unamortized Debt Issuance Expense		$ (19,203)			$ (3,300)
Debt, Weighted Average Interest Rate			3.68%
Contractual Quarterly Payments		2,100
Payments on Debt		$ 71,000
$825 Million Term B Loan Facility and $150 Million Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount				$ 975,000
$825 Million Term B Loan Facility, due June 2022 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount				825,000
$150 Million Revolving Credit Facility, Due June 2020 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount				$ 150,000
Maximum [Member]
Debt Instrument [Line Items]
Leverage Ratio		4.50
Leverage Ratio in Latest Year of Debt Term		3.25
Notes Payable to Banks [Member] \| Minimum [Member] \| $150 Million Revolving Credit Facility, Due June 2020 [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate \| Rate	0.75%
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage \| Rate	0.00%
Notes Payable to Banks [Member] \| Maximum [Member] \| $150 Million Revolving Credit Facility, Due June 2020 [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate \| Rate	2.50%
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage \| Rate	0.00%
Notes Payable to Banks [Member] \| Maximum [Member] \| Eurodollar [Member] \| $825 Million Term B Loan Facility, due June 2022 [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate \| Rate	3.00%
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Remaining Borrowing Capacity		$ 96,300