Number of persons employed by the Entity

No definition available.

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Namespace Prefix:	dei_
Data Type:	xbrli:decimalItemType
Balance Type:	na
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- Definition

This element represents acquisition-related costs incurred to effect a business combination which costs have been expensed during the period. Such costs include finder's fees; advisory, legal, accounting, valuation, and other professional or consulting fees; general administrative costs, including the costs of maintaining an internal acquisitions department; and may include costs of registering and issuing debt and equity securities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 25
-Paragraph 23
-URI http://asc.fasb.org/extlink&oid=84229725&loc=d3e1043-128460

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of consideration transferred, consisting of acquisition-date fair value of assets transferred by the acquirer, liabilities incurred by the acquirer, and equity interest issued by the acquirer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 30
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=6911251&loc=d3e6578-128477

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=35744584&loc=d3e6927-128479

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 30
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=6911251&loc=d3e6613-128477

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- 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

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of increase in assets, excluding financial assets, lacking physical substance with a definite life, from an acquisition.

+ References

No definition available.

+ Details

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

- 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://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267

+ Details

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

- Details

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Namespace Prefix:
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Period Type:

- Details

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

- Details

Name:	us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis=us-gaap_ComputerSoftwareIntangibleAssetMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis=us-gaap_TradeNamesMember
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Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_IncomeStatementLocationAxis=us-gaap_SellingGeneralAndAdministrativeExpensesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BusinessAcquisitionAxis=fds_VermilionHoldingsLimitedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis=us-gaap_NoncompeteAgreementsMember
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Data Type:	na
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- Details

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- Details

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- Details

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Note 8 - Business Combinations (Details Textual) $ in Millions			12 Months Ended
	Mar. 17, 2017 USD ($)	Nov. 08, 2016 USD ($)	Aug. 31, 2017 USD ($)
BI-SAM Technologies [Member] \| Customer Relationships [Member]
Finite-Lived Intangible Asset, Useful Life	16 years
BI-SAM Technologies [Member] \| Computer Software, Intangible Asset [Member]
Finite-Lived Intangible Asset, Useful Life	5 years
BI-SAM Technologies [Member] \| Trade Names [Member]
Finite-Lived Intangible Asset, Useful Life	4 years
BI-SAM Technologies [Member] \| Selling, General and Administrative Expenses [Member]
Business Combination, Acquisition Related Costs			$ 3.2
Vermilion Holdings Limited [Member]
Business Combination, Consideration Transferred		$ 67.9
Vermilion Holdings Limited [Member] \| Customer Relationships [Member]
Finite-Lived Intangible Asset, Useful Life		15 years
Vermilion Holdings Limited [Member] \| Computer Software, Intangible Asset [Member]
Finite-Lived Intangible Asset, Useful Life		6 years
Vermilion Holdings Limited [Member] \| Trade Names [Member]
Finite-Lived Intangible Asset, Useful Life		4 years
Vermilion Holdings Limited [Member] \| Noncompete Agreements [Member]
Finite-Lived Intangible Asset, Useful Life		3 years
Vermilion Holdings Limited [Member] \| Selling, General and Administrative Expenses [Member]
Business Combination, Acquisition Related Costs			$ 0.7
BI-SAM Technologies [Member]
Business Combination, Consideration Transferred	$ 217.6
Finite-lived Intangible Assets Acquired	56.6
Goodwill, Acquired During Period	$ 173.9
BI-SAM Technologies [Member] \| Minimum [Member]
Entity Number of Employees	160
Vermilion Holdings Limited [Member]
Entity Number of Employees		59
Finite-lived Intangible Assets Acquired		$ 18.2
Goodwill, Acquired During Period		$ 51.2