Basis of Presentation and Nature of Business - Additional Information (Details)		9 Months Ended
Jul. 02, 2021	Sep. 30, 2021
Basis Of Presentation And Nature Of Business [Line Items]
Date of incorporation		Mar. 26, 2020
Foley Trasimene Acquisition Corp
Basis Of Presentation And Nature Of Business [Line Items]
Business combination, closing date of acquisition	Jul. 02, 2021
Foley Trasimene Acquisition Corp \| Alight Holdings
Basis Of Presentation And Nature Of Business [Line Items]
Non-voting ownership percentage held by noncontrolling interest	15.00%
Alight \| Foley Trasimene Acquisition Corp \| Alight Holdings
Basis Of Presentation And Nature Of Business [Line Items]
Percentage of economic interest	85.00%
Business combination, percentage of voting power	100.00%

Basis of presentation and nature of business.

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- Definition

Date when an entity was incorporated

+ References

No definition available.

+ Details

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- Definition

Date when the acquirer obtains control of the acquiree, in CCYY-MM-DD format.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 25
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=116868678&loc=d3e848-128460

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 25
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=116868678&loc=d3e845-128460

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=79982066&loc=d3e1392-128463

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- Definition

Percentage of voting equity interests acquired at the acquisition date in the business combination.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=79982066&loc=d3e1392-128463

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- Definition

The equity interest of noncontrolling shareholders, partners or other equity holders in consolidated entity.

+ References

No definition available.

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- Definition

The parent entity's interest in net assets of the subsidiary, expressed as a percentage.

+ References

No definition available.

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