Percentage of adjusted earnings before interest tax depreciation and amortization.

No definition available.

Name:	adth_PercentageOfAdjustedEarningsBeforeInterestTaxDepreciationAndAmortization
Namespace Prefix:	adth_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Share based compensation by share based award date of vesting.

+ References

No definition available.

+ Details

Name:	adth_ShareBasedCompensationByShareBasedAwardDateOfVesting
Namespace Prefix:	adth_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Tax benefits from equity options excercised.

+ References

No definition available.

+ Details

Name:	adth_TaxBenefitsFromEquityOptionsExcercised
Namespace Prefix:	adth_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5047-113901

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 14.F)
-URI http://asc.fasb.org/extlink&oid=122041274&loc=d3e301413-122809

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(1)(i)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901

+ Details

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

- 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

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

- Definition

Amount of tax benefit for recognition of expense of award under share-based payment arrangement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(1)(i)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901

+ Details

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

- Definition

Amount of cash inflow from exercise of option under share-based payment arrangement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2A
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=SL79508275-113901

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123570139&loc=d3e3255-108585

+ Details

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

- Definition

Estimated period over which an employee is required to provide service in exchange for the equity-based payment award, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardRequisiteServicePeriod1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(1)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(1)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of shares authorized for issuance under share-based payment arrangement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)(3)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Gross number of share options (or share units) granted during the period.

+ References

No definition available.

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options.

+ References

No definition available.

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of vesting of award under share-based payment arrangement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901

+ Details

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

- Definition

Period from grant date that an equity-based award expires, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)(2)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901

+ Details

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

- Details

Name:	adth_EventAxis=adth_MilestoneAchievedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardTypeAxis=us-gaap_EmployeeStockOptionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardTypeAxis=adth_RestrictedIncentiveUnitsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PlanNameAxis=adth_MemberIncentivePlanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementClassOfStockAxis=adth_NonVotingClassCCommonUnitsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	adth_VestingCriteriaAxis=adth_TimeBasedVestingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	adth_VestingCriteriaAxis=adth_PerformanceBasedVestingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_TitleOfIndividualAxis=adth_CertainDirectorsAndOfficersMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	adth_MilestoneAxis=adth_MilestoneOneMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	adth_MilestoneAxis=adth_MilestoneTwoMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	adth_MilestoneAxis=adth_MilestoneThreeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	adth_MilestoneAxis=adth_MilestoneFourMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	adth_VestingSubtrancheAxis=adth_VestingSubtrancheOneMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VestingAxis=us-gaap_ShareBasedCompensationAwardTrancheOneMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VestingAxis=us-gaap_ShareBasedCompensationAwardTrancheTwoMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	adth_VestingSubtrancheAxis=adth_VestingSubtrancheTwoMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	adth_VestingSubtrancheAxis=adth_VestingSubtrancheThreeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	adth_VestingSubtrancheAxis=adth_VestingSubtrancheFourMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Equity-Based Compensation Expense - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands		9 Months Ended		12 Months Ended
	Jul. 28, 2021	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Proceeds from the exercise of stock options		$ 18	$ 33	$ 101	$ 3
Share based compensation income tax expense benefit		105	161	181	214
Allocated share based compensation expense		382	547	657	776
Tax benefit from equity options excercised		6	10	28	1
Milestone Achieved [Member]
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Allocated share based compensation expense		382	547	$ 136	$ 197
Share-based Payment Arrangement, Option
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Allocated share based compensation expense		$ 63	$ 123
Restricted Incentive Units
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share based compensation by share based award equity instruments other than options granted		541,900
Share based compensation by share based award equity instruments other than options granted weighted average fair value at grant date		$ 16.12
Member Incentive Plan
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share based compensation by share based award number of options granted during the period					2,547,500
Share based compensation by share based award weighted average exercise price of options granted during the period				$ 1.00	$ 1.15
Member Incentive Plan \| Non Voting Class C Common Units
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share based compensation by share based award number of shares authorized for grant				5,850,000
Share based compensation by share based award number of shares available for grant		189,725		725,375
Member Incentive Plan \| Non Voting Class C Common Units \| Share-based Payment Arrangement, Option
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share based compensation by share based award term				10 years
Share based compensation by share based award number of options granted during the period		0	0	0	2,547,500
Member Incentive Plan \| Non Voting Class C Common Units \| Share-based Payment Arrangement, Option \| Time Based Vesting [Member]
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share based compensation by share based award vesting percentage				25.00%
Share based compensation by share based payment award requisite period				4 years
Member Incentive Plan \| Non Voting Class C Common Units \| Share-based Payment Arrangement, Option \| Performance Based Vesting [Member]
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share based compensation by share based award vesting percentage				25.00%
Share based compensation by share based award vesting period				4 years
Member Incentive Plan \| Non Voting Class C Common Units \| Share-based Payment Arrangement, Option \| Performance Based Vesting [Member] \| Certain Directors And Officers
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share based compensation by share based award number of options granted during the period					2,547,500
Share based compensation by share based award weighted average exercise price of options granted during the period					$ 1.15
Member Incentive Plan \| Non Voting Class C Common Units \| Share-based Payment Arrangement, Option \| Performance Based Vesting [Member] \| Certain Directors And Officers \| Milestone One [Member]
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share based compensation by share based award vesting percentage					25.00%
Share based compensation by share based award vesting period					12 months
Percentage of adjusted earnings before interest tax depreciation and amortization					90.00%
Share based compensation by share based award date of vesting					Dec. 31, 2019
Member Incentive Plan \| Non Voting Class C Common Units \| Share-based Payment Arrangement, Option \| Performance Based Vesting [Member] \| Certain Directors And Officers \| Milestone Two [Member]
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share based compensation by share based award vesting percentage					25.00%
Share based compensation by share based award vesting period					12 months
Percentage of adjusted earnings before interest tax depreciation and amortization					90.00%
Share based compensation by share based award date of vesting					Dec. 31, 2020
Member Incentive Plan \| Non Voting Class C Common Units \| Share-based Payment Arrangement, Option \| Performance Based Vesting [Member] \| Certain Directors And Officers \| Milestone Three [Member]
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share based compensation by share based award vesting percentage					25.00%
Share based compensation by share based award vesting period					12 months
Percentage of adjusted earnings before interest tax depreciation and amortization					90.00%
Share based compensation by share based award date of vesting					Dec. 31, 2021
Member Incentive Plan \| Non Voting Class C Common Units \| Share-based Payment Arrangement, Option \| Performance Based Vesting [Member] \| Certain Directors And Officers \| Milestone Four [Member]
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share based compensation by share based award vesting percentage					25.00%
Share based compensation by share based award vesting period					12 months
Percentage of adjusted earnings before interest tax depreciation and amortization					90.00%
Share based compensation by share based award date of vesting					Dec. 31, 2022
Member Incentive Plan \| Non Voting Class C Common Units \| Restricted Incentive Units
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share based compensation by share based award term				10 years
Share based compensation by share based award equity instruments other than options granted	541,900	541,900	0
Share based compensation by share based award equity instruments other than options granted weighted average fair value at grant date	$ 16.12
Member Incentive Plan \| Non Voting Class C Common Units \| Restricted Incentive Units \| Vesting Subtranche One [Member]
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share based compensation by share based award vesting percentage	12.50%
Member Incentive Plan \| Non Voting Class C Common Units \| Restricted Incentive Units \| Share-based Payment Arrangement, Tranche One [Member]
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share based compensation by share based award vesting percentage	50.00%
Member Incentive Plan \| Non Voting Class C Common Units \| Restricted Incentive Units \| Share-based Payment Arrangement, Tranche Two [Member]
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share based compensation by share based award vesting percentage	50.00%
Member Incentive Plan \| Non Voting Class C Common Units \| Restricted Incentive Units \| Share-based Payment Arrangement, Tranche Two [Member] \| Vesting Subtranche Two [Member]
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share based compensation by share based award vesting percentage	12.50%
Member Incentive Plan \| Non Voting Class C Common Units \| Restricted Incentive Units \| Share-based Payment Arrangement, Tranche Two [Member] \| Vesting Subtranche Three [Member]
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share based compensation by share based award vesting percentage	12.50%
Member Incentive Plan \| Non Voting Class C Common Units \| Restricted Incentive Units \| Share-based Payment Arrangement, Tranche Two [Member] \| Vesting Subtranche Four [Member]
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share based compensation by share based award vesting percentage	12.50%