Business combination, contingent consideration, liability expected holding period.

No definition available.

Name:	alit_BusinessCombinationContingentConsiderationLiabilityExpectedHoldingPeriod
Namespace Prefix:	alit_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The seller earnout fair value of shares that would be issued, determined under the conditions specified in the contract if the settlement were to occur at the reporting date.

+ References

No definition available.

+ Details

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Namespace Prefix:	alit_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Loss (gain) from change in fair value of seller earnouts.

+ References

No definition available.

+ Details

Name:	alit_LossGainFromChangeInFairValueOfSellerEarnouts
Namespace Prefix:	alit_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Value of input used to measure contingent consideration liability from business combination.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)
-URI https://asc.fasb.org/extlink&oid=126976982&loc=d3e19207-110258

+ Details

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Balance Type:	na
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
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- Details

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Namespace Prefix:
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- Details

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Namespace Prefix:
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- Details

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- Details

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Data Type:	na
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Period Type:

Financial Instruments - Seller Earnouts - Additional Information (Details) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2023 USD ($)	Mar. 31, 2022 USD ($)	Dec. 31, 2022 USD ($)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair value of seller earnouts	$ 109		$ 96
Loss (gain) from change in fair value of seller earnouts	(13)	$ 14
Common Class Z [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Loss (gain) from change in fair value of seller earnouts	$ 12	$ 1
Seller Earnouts Liability
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Business combination, contingent consideration, liability expected holding period	5 years 3 months 3 days
Seller Earnouts Liability \| Volatility
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement Input	50
Seller Earnouts Liability \| Risk-free Interest Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement Input	3.59