Earnings Per Share - Additional Information (Detail)	Mar. 31, 2020 Class
Earnings Per Share
Number of classes of common stock	2

The number of classes of common stock of the entity.

No definition available.

Name:	ttd_CommonStockNumberOfClasses
Namespace Prefix:	ttd_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant