Debt instruments maturity month and year.

No definition available.

Name:	alsn_DebtInstrumentsMaturityMonthAndYear
Namespace Prefix:	alsn_
Data Type:	xbrli:gYearMonthItemType
Balance Type:	na
Period Type:	instant

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

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+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
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.

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+ Details

Name:	us-gaap_DebtInstrumentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

End date of debt instrument redemption period, in YYYY-MM-DD format.

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

- Definition

Percentage price of original principal amount of debt at which debt can be redeemed by the issuer.

+ References

+ Details

Name:	us-gaap_DebtInstrumentRedemptionPricePercentage
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

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+ Details

Name:	us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount, after deduction of unamortized premium (discount) and debt issuance cost, of long-term debt. Excludes lease obligation.

+ References

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+ Details

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

- Definition

The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

+ References

No definition available.

+ Details

Name:	us-gaap_LongTermDebtFairValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The cash outflow for loan and debt issuance costs.

+ References

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Period Type:	duration

- Details

Name:	us-gaap_DebtInstrumentAxis=alsn_FourPointSevenFivePercentageSeniorNotesDue2027Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=alsn_FivePointEightSevenFivePercentageSeniorNotesDue2029Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=alsn_ThreePointSevenFivePercentageSeniorNotesDue2031Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=alsn_SeniorSecuredCreditFacilityTermLoanVariableDue2031Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentRedemptionPeriodAxis=us-gaap_DebtInstrumentRedemptionPeriodOneMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentRedemptionPeriodAxis=us-gaap_DebtInstrumentRedemptionPeriodTwoMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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Namespace Prefix:
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Debt - Additional Information (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023
Debt Instrument [Line Items]
Long-term debt	$ 2,417		$ 2,518
Fair value of long-term debt obligations	2,276
Deferred financing fees	4	$ 0
Senior Notes, Fixed 4.75%, Due 2027
Debt Instrument [Line Items]
Long-term debt	$ 400		$ 400
Debt instrument, stated interest rate	4.75%		4.75%
Debt instrument, maturity month and year	2027-10
Senior Notes, Fixed 5.875%, Due 2029
Debt Instrument [Line Items]
Long-term debt	$ 500		$ 500
Debt instrument, stated interest rate	5.875%		5.875%
Debt instrument, maturity month and year	2029-06
Senior Notes, Fixed 3.75%, Due 2031
Debt Instrument [Line Items]
Long-term debt	$ 1,000		$ 1,000
Debt instrument, stated interest rate	3.75%		3.75%
Debt instrument, maturity month and year	2031-01
Senior Secured Credit Facility Term Loan, variable, due 2031
Debt Instrument [Line Items]
Long-term debt	$ 517		$ 0
Debt instrument, maturity month and year	2031-03
Debt Instrument, Redemption, Period One \| Senior Notes, Fixed 3.75%, Due 2031
Debt Instrument [Line Items]
Debt instrument, redemption end date	Jan. 30, 2026
Percentage of principal amount redeemed	100.00%
Debt Instrument, Redemption, Period Two \| Senior Notes, Fixed 3.75%, Due 2031
Debt Instrument [Line Items]
Debt instrument, redemption end date	Jan. 30, 2026
Revolving Credit Facility
Debt Instrument [Line Items]
Debt instrument, maturity month and year	2029-03
Credit facility, commitments amount	$ 750