Basis of presentation and nature of business.

No definition available.

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Namespace Prefix:	alit_
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Period Type:	duration

- Definition

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

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 25
-Paragraph 7
-SubTopic 10
-Topic 805
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479405/805-10-25-7

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (b)
-SubTopic 10
-Topic 805
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479328/805-10-50-2

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 25
-Paragraph 6
-SubTopic 10
-Topic 805
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479405/805-10-25-6

+ Details

Name:	us-gaap_BusinessAcquisitionEffectiveDateOfAcquisition1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- 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
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479328/805-10-50-2

+ Details

Name:	us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

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

+ References

No definition available.

+ Details

Name:	us-gaap_MinorityInterestOwnershipPercentageByNoncontrollingOwners
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

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

+ References

No definition available.

+ Details

Name:	us-gaap_MinorityInterestOwnershipPercentageByParent
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	srt_OwnershipAxis=alit_AlightHoldingsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	srt_ConsolidatedEntitiesAxis=alit_AlightGroupIncMember
Namespace Prefix:
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Basis of Presentation and Nature of Business - Additional Information (Details)	Jul. 02, 2021	Dec. 31, 2023
Alight Holdings
Basis Of Presentation And Nature Of Business [Line Items]
Non-voting ownership percentage held by noncontrolling interest		5.00%
Special Purpose Acquisition Company
Basis Of Presentation And Nature Of Business [Line Items]
Business combination, closing date of acquisition	Jul. 02, 2021
Alight \| Special Purpose Acquisition Company \| Alight Holdings
Basis Of Presentation And Nature Of Business [Line Items]
Percentage of economic interest		95.00%
Business combination, percentage of voting power	100.00%