Commitments and Contingencies - Summary of Future Minimum Payments (Details) $ in Thousands	Mar. 31, 2020 USD ($)
Leases
Lessee, Lease Liability, Payments Remainder Of Fiscal Year	$ 11,506
2021	14,349
2022	13,649
2023	12,658
2024 and thereafter	27,846
Total lease payments	80,008
Other Commitments
2020, excluding the three months ended March 31, 2020	8,716
2021	4,780
2022	5,439
2023	0
2024 and thereafter	0
Total future minimum payments	$ 18,935

Lessee, Lease Liability, Payments, Due

No definition available.

Name:	rdfn_LesseeLeaseLiabilityPaymentsDue
Namespace Prefix:	rdfn_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Lessee, Lease Liability, Payments, Due Year Five And Thereafter

+ References

No definition available.

+ Details

Name:	rdfn_LesseeLeaseLiabilityPaymentsDueYearFiveAndThereafter
Namespace Prefix:	rdfn_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Lessee, Lease Liability, Payments, Due Year Four

+ References

No definition available.

+ Details

Name:	rdfn_LesseeLeaseLiabilityPaymentsDueYearFour
Namespace Prefix:	rdfn_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Lessee, Lease Liability, Payments, Due Year Three

+ References

No definition available.

+ Details

Name:	rdfn_LesseeLeaseLiabilityPaymentsDueYearThree
Namespace Prefix:	rdfn_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Lessee, Lease Liability, Payments, Due Year Two

+ References

No definition available.

+ Details

Name:	rdfn_LesseeLeaseLiabilityPaymentsDueYearTwo
Namespace Prefix:	rdfn_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Lessee, Lease Liability, Payments Remainder Of Fiscal Year

+ References

No definition available.

+ Details

Name:	rdfn_LesseeLeaseLiabilityPaymentsRemainderOfFiscalYear
Namespace Prefix:	rdfn_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Other Commitment, Due in Fifth Year and Thereafter

+ References

No definition available.

+ Details

Name:	rdfn_OtherCommitmentDueinFifthYearandThereafter
Namespace Prefix:	rdfn_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- References

No definition available.

+ Details

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

- Definition

Minimum amount of other commitment not otherwise specified in the taxonomy. Excludes commitments explicitly modeled in the taxonomy, including but not limited to, long-term and short-term purchase commitments, recorded and unrecorded purchase obligations, supply commitments, registration payment arrangements, leases, debt, product warranties, guarantees, environmental remediation obligations, and pensions.

+ References

No definition available.

+ Details

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

- Definition

Minimum amount of other commitment maturing in the fourth fiscal year following the latest fiscal year for commitments not otherwise specified in the taxonomy. Excludes commitments explicitly modeled in this taxonomy, including but not limited to, long-term and short-term purchase commitments, recorded and unrecorded purchase obligations, supply commitments, registration payment arrangements, leases, debt, product warranties, guarantees, environmental remediation obligations, and pensions.

+ References

No definition available.

+ Details

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

- Definition

Minimum amount of other commitment maturing in the second fiscal year following the latest fiscal year for commitments not otherwise specified in the taxonomy. Excludes commitments explicitly modeled in this taxonomy, including but not limited to, long-term and short-term purchase commitments, recorded and unrecorded purchase obligations, supply commitments, registration payment arrangements, leases, debt, product warranties, guarantees, environmental remediation obligations, and pensions.

+ References

No definition available.

+ Details

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

- Definition

Minimum amount of other commitment maturing in the third fiscal year following the latest fiscal year for commitments not otherwise specified in the taxonomy. Excludes commitments explicitly modeled in this taxonomy, including but not limited to, long-term and short-term purchase commitments, recorded and unrecorded purchase obligations, supply commitments, registration payment arrangements, leases, debt, product warranties, guarantees, environmental remediation obligations, and pensions.

+ References

No definition available.

+ Details

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

- References

No definition available.

+ Details

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

- Definition

Amount of other commitments maturing in the remainder of the fiscal year following the latest fiscal year ended.

+ References

No definition available.

+ Details

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