DEBT - Warehouse Facilities (Detail) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
Sep. 30, 2024	Dec. 31, 2023
Warehouse notes payable
Outstanding Balance	$ 1,019,850	$ 596,178
Loans Held for Sale \| Agency Warehouse Facility
Warehouse notes payable
Committed Amount	1,650,000
Uncommitted Amount	3,650,000
Total Facility Capacity	5,300,000
Outstanding Balance	1,008,534
National Banks \| Loans Held for Sale \| Agency Warehouse Facility
Warehouse notes payable
Committed Amount	1,650,000
Uncommitted Amount	2,150,000
Total Facility Capacity	3,800,000
Outstanding Balance	951,553
National Banks \| Loans Held for Sale \| Agency Warehouse Facility #1 \| Agency Warehouse Facility
Warehouse notes payable
Committed Amount	325,000
Uncommitted Amount	250,000
Total Facility Capacity	575,000
Outstanding Balance	$ 161,956
Percentage added to reference rate	1.30%
Maturity date	Aug. 27, 2025
National Banks \| Loans Held for Sale \| Agency Warehouse Facility #2 \| Agency Warehouse Facility
Warehouse notes payable
Committed Amount	$ 700,000
Uncommitted Amount	300,000
Total Facility Capacity	1,000,000
Outstanding Balance	$ 215,752
Percentage added to reference rate	1.30%
Maturity date	Apr. 11, 2025
National Banks \| Loans Held for Sale \| Agency Warehouse Facility #3 \| Agency Warehouse Facility
Warehouse notes payable
Committed Amount	$ 425,000	600,000
Uncommitted Amount	425,000	$ 265,000
Total Facility Capacity	850,000
Outstanding Balance	$ 214,877
Percentage added to reference rate	1.30%	1.35%
Debt instrument, Variable interest rate, Type	us-gaap:SecuredOvernightFinancingRateSofrMember	us-gaap:SecuredOvernightFinancingRateSofrMember
Maturity date	May 15, 2025
National Banks \| Loans Held for Sale \| Agency Warehouse Facility #4 \| Agency Warehouse Facility
Warehouse notes payable
Committed Amount	$ 150,000	$ 200,000
Uncommitted Amount	225,000
Total Facility Capacity	375,000
Outstanding Balance	$ 89,593
Maturity date	Jun. 22, 2025
National Banks \| Loans Held for Sale \| Agency Warehouse Facility #4 \| Agency Warehouse Facility \| Minimum
Warehouse notes payable
Percentage added to reference rate	1.30%
National Banks \| Loans Held for Sale \| Agency Warehouse Facility #4 \| Agency Warehouse Facility \| Maximum
Warehouse notes payable
Percentage added to reference rate	1.35%
National Banks \| Loans Held for Sale \| Agency Warehouse Facility #5 \| Agency Warehouse Facility
Warehouse notes payable
Committed Amount	$ 50,000
Uncommitted Amount	950,000	$ 1,000,000
Total Facility Capacity	1,000,000
Outstanding Balance	$ 269,375
Percentage added to reference rate	1.45%
Maturity date	Sep. 11, 2025
National Banks \| Loans Held for Investment \| Interim Warehouse Facility
Warehouse notes payable
Total Facility Capacity	$ 119,800
Outstanding Balance	$ 11,700
National Banks \| Loans Held for Investment \| Interim Warehouse Facility \| Minimum
Warehouse notes payable
Percentage added to reference rate	2.50%
Debt instrument, Variable interest rate, Type	us-gaap:SecuredOvernightFinancingRateSofrMember
National Banks \| Loans Held for Investment \| Interim Warehouse Facility \| Maximum
Warehouse notes payable
Percentage added to reference rate	3.11%
Debt instrument, Variable interest rate, Type	us-gaap:SecuredOvernightFinancingRateSofrMember
Fannie Mae \| Loans Held for Sale \| Fannie Mae Repurchase Agreement, Uncommitted Line and Open Maturity \| Agency Warehouse Facility
Warehouse notes payable
Uncommitted Amount	$ 1,500,000
Total Facility Capacity	1,500,000
Outstanding Balance	$ 56,981

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

No definition available.

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

- Definition

Indicates type of variable interest rate on debt instrument.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 470
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477734/942-470-50-3

+ Details

Name:	us-gaap_DebtInstrumentVariableInterestRateTypeExtensibleEnumeration
Namespace Prefix:	us-gaap_
Data Type:	enum2:enumerationSetItemType
Balance Type:	na
Period Type:	duration

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions 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
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-SubTopic 10
-Topic 210
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 942
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478546/942-210-S99-1

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 944
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(16)(a)(2))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478777/944-210-S99-1

+ Details

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

- Definition

Date the credit facility terminates, in YYYY-MM-DD format.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22)(b))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(19)(b))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

+ Details

Name:	us-gaap_LineOfCreditFacilityExpirationDate1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
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

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481544/470-10-50-6

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481544/470-10-50-6

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(f))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480678/235-10-S99-1

+ Details

Name:	us-gaap_LineOfCreditFacilityLineItems
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

Maximum committed borrowing capacity under a credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

No definition available.

+ Details

Name:	wd_LineOfCreditFacilityCommittedBorrowingCapacity
Namespace Prefix:	wd_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Maximum uncommitted 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

No definition available.

+ Details

Name:	wd_LineOfCreditFacilityUncommittedBorrowingCapacity
Namespace Prefix:	wd_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	us-gaap_InvestmentTypeAxis=wd_LoansHeldForSaleMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=wd_AgencyWarehouseFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_CounterpartyNameAxis=wd_NationalBanksMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

Name:	us-gaap_InvestmentTypeAxis=wd_LoansHeldForInvestmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=wd_InterimWarehouseFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_CounterpartyNameAxis=wd_FannieMaeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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