Line of credit maximum amount right to increase.

No definition available.

Name:	ttd_LineOfCreditMaximumAmountRightToIncrease
Namespace Prefix:	ttd_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Maximum ratio of consolidated funded debt to consolidated EBITDA.

+ References

No definition available.

+ Details

Name:	ttd_MaximumRatioOfConsolidatedFundedDebtToConsolidatedEBITDA
Namespace Prefix:	ttd_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Description of reference rate used for variable rate of debt instrument.

+ References

No definition available.

+ Details

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

- Definition

Date when the debt instrument is scheduled to be fully repaid, in YYYY-MM-DD format.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(2))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1B
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495323-112611

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
-Section 50
-Paragraph 2
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-URI http://asc.fasb.org/extlink&oid=123874694&loc=d3e19207-110258

+ Details

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

- Definition

Fair value of the amount outstanding under the credit facility.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=123594938&loc=d3e13433-108611

+ Details

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

- Definition

Description of interest rate for borrowing under credit facility. Includes, but is not limited to, terms and method for determining interest rate.

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityInterestRateDescription
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
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.

+ References

+ Details

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

- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

+ Details

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

- Definition

The fee, expressed as a percentage of the line of credit facility, for available but unused credit capacity under the credit facility.

+ References

No definition available.

+ Details

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

- Definition

The carrying value as of the balance sheet date of the noncurrent portion of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22)
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
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+ Details

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

- Details

Name:	us-gaap_CreditFacilityAxis=ttd_LoanAndSecurityAgreementRevolvingLoanFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=ttd_LoanAndSecurityAgreementRevolvingLoanFacilitySwinglineBorrowingsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=ttd_LoanAndSecurityAgreementRevolvingLoanFacilityLettersOfCreditMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MinimumMember
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Balance Type:
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- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=us-gaap_LondonInterbankOfferedRateLIBORMember
Namespace Prefix:
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Balance Type:
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- Details

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Debt - Additional Information (Detail) - USD ($)		12 Months Ended
Debt - Additional Information (Detail) - USD ($)	Jun. 15, 2021	Dec. 31, 2021
Loan and Security Agreement Revolving Loan Facility
Long-term debt:
Line of credit facility	$ 450,000,000.0
Loan and Security Agreement Revolving Loan Facility Swingline Borrowings
Long-term debt:
Line of credit facility	20,000,000.0
Loan and Security Agreement Revolving Loan Facility Letter of Credit
Long-term debt:
Line of credit facility	15,000,000.0
Outstanding letters of credit		$ 6,100,000
Loan and Security Agreement
Long-term debt:
Line of credit maximum amount right to increase	$ 300,000,000.0
Interest rate description		The Base Rate is defined as a rate per annum for any day equal to the greatest of (1) the rate of interest last quoted by The Wall Street Journal as the “Prime Rate” in the United States, (2) the NYFRB Rate in effect on such day plus half of 1% and (3) the adjusted LIBOR rate for a one-month interest period on such day plus 1%. The applicable margin is between 0.25% to 1.25% for Base Rate Borrowings and between 1.25% and 2.25% for LIBOR Rate Borrowings based on the Company maintaining certain leverage ratios.
Outstanding debt balance		$ 0
Availability under the credit facility		$ 443,900,000
Credit facility, maturity		Jun. 15, 2026
Maximum ratio of consolidated funded debt to consolidated EBITDA		350.00%
Loan and Security Agreement \| Minimum
Long-term debt:
Fee percentage for undrawn amounts		0.20%
Loan and Security Agreement \| Maximum
Long-term debt:
Fee percentage for undrawn amounts		0.35%
Loan and Security Agreement \| NYFRB Rate
Long-term debt:
Description of variable rate basis		day plus half of 1%
Basis spread on variable rate		1.00%
Loan and Security Agreement \| LIBOR Rate
Long-term debt:
Description of variable rate basis		one-month interest period on such day plus 1%
Basis spread on variable rate		1.00%
Loan and Security Agreement \| LIBOR Rate \| Minimum
Long-term debt:
Basis spread on variable rate		1.25%
Loan and Security Agreement \| LIBOR Rate \| Maximum
Long-term debt:
Basis spread on variable rate		2.25%
Loan and Security Agreement \| Base Rate \| Minimum
Long-term debt:
Basis spread on variable rate		0.25%
Loan and Security Agreement \| Base Rate \| Maximum
Long-term debt:
Basis spread on variable rate		1.25%