v3.6.0.2

Basis of Presentation and Summary of Significant Accounting Policies - Property and Equipment, Net (Detail)	12 Months Ended
	Dec. 31, 2016
Computer Equipment
Property, Plant and Equipment [Line Items]
Property and equipment, useful life	2 years
Purchased Software
Property, Plant and Equipment [Line Items]
Property and equipment, useful life	5 years
Furniture, fixtures and office equipment
Property, Plant and Equipment [Line Items]
Property and equipment, useful life	5 years
Leasehold Improvements
Property, Plant and Equipment [Line Items]
Property and equipment, useful life		[1]
[1] Leasehold improvements are amortized on a straight-line basis over the term of the lease, or the useful life of the assets, whichever is shorter.

X

- Definition

Describes the periods of time over which an entity anticipates to receive utility from its property, plant and equipment (that is, the periods of time over which an entity allocates the initial cost of its property, plant and equipment).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=68058157&loc=d3e18780-107790

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 35
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=68071081&loc=d3e1205-110223

+ Details

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

X

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

X

- Definition

Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

+ References

No definition available.

+ Details

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

X

- Details

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

X

- Details

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

X

- Details

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=ttd_FurnitureFixturesAndOfficeEquipmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_LeaseholdImprovementsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: