The amount of adjustment to additional paid in capital for consulting service fee.

No definition available.

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Namespace Prefix:	tw_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The amount of consulting service incurred for follow on offering.

+ References

No definition available.

+ Details

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Namespace Prefix:	tw_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The amount of consulting service incurred for IPO.

+ References

No definition available.

+ Details

Name:	tw_ConsultingServiceFeeForIpo
Namespace Prefix:	tw_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Expenses recognized resulting from transactions (excluding transactions that are eliminated in consolidated or combined financial statements) with related party.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 850
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39549-107864

+ Details

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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

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

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Namespace Prefix:
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Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionAxis=tw_OperatingExpenseReimbursementMember
Namespace Prefix:
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Related Party Transactions - Narrative (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended				9 Months Ended
	Apr. 30, 2019	Sep. 30, 2020	Jun. 30, 2020	Dec. 31, 2019	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Related Party Transactions
Consulting service fee for IPO	$ 1.0
Consulting service fee for follow on offering			$ 0.5	$ 0.5
Adjustment to additional paid in capital due to consulting service fee						$ 2.0
Refinitiv \| Operating Expense Reimbursement
Related Party Transactions
Related party expense		$ 0.1			$ 1.2	$ 1.3	$ 5.5