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:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The reference rate for the variable rate of the debt instrument, such as LIBOR or the US Treasury rate and the maturity of the reference rate used, such as three months or six months LIBOR.

+ References

No definition available.

+ Details

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

- Definition

Amount, after accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28555-108399

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.17)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_DeferredFinanceCostsNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- 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://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(16))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

+ 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 CCYY-MM-DD format.

+ References

+ 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

No definition available.

+ 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

Temporary increase in maximum borrowing capacity under the credit facility.

+ References

No definition available.

+ Details

Name:	wd_LineOfCreditFacilityTemporaryIncreaseToMaximumBorrowingCapacity
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

- Definition

Amount of maximum uncommitted borrowing capacity under the credit facility while the temporary increase to the facility is outstanding.

+ References

No definition available.

+ Details

Name:	wd_LineOfCreditFacilityUncommittedBorrowingCapacityWhileTemporaryIncreaseOutstanding
Namespace Prefix:	wd_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The number of lenders removed from the credit facility agreement.

+ References

No definition available.

+ Details

Name:	wd_NumberOfLendersRemovedFromCreditFacility
Namespace Prefix:	wd_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_CreditFacilityAxis=wd_LineOfCreditAgencyWarehouseFacilityOneMember
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:	us-gaap_VariableRateAxis=us-gaap_LondonInterbankOfferedRateLIBORMember
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_DebtInstrumentRedemptionPeriodAxis=us-gaap_DebtInstrumentRedemptionPeriodOneMember
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:	us-gaap_CreditFacilityAxis=wd_LineOfCreditAgencyWarehouseFacilityFiveMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=wd_LineOfCreditAgencyWarehouseFacilitySixMember
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:

- Details

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

- Details

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

- Details

Name:	us-gaap_RangeAxis=us-gaap_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	us-gaap_CounterpartyNameAxis=wd_FannieMaeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

WAREHOUSE NOTES PAYABLE - Schedule of Debt (Details) $ in Thousands	3 Months Ended			9 Months Ended
	Dec. 31, 2017	Sep. 30, 2017 USD ($) Lender	Jun. 30, 2017 USD ($)	Sep. 30, 2017 USD ($)	Dec. 31, 2016 USD ($)
Warehouse notes payable
Committed Amount		$ 2,395,000		$ 2,395,000
Uncommitted Amount		1,750,000		1,750,000
Temporary Increase		2,466,000		2,466,000
Total Facility Capacity		6,611,000		6,611,000	$ 4,000,000
Outstanding Balance		3,305,589		3,305,589	$ 1,990,183
Debt issuance costs		(218)		$ (218)
Agency Warehouse Facility #1 \| Agency Warehouse Facility
Warehouse notes payable
Maturity date	Nov. 30, 2017
Agency Warehouse Facility #1 \| Agency Warehouse Facility \| LIBOR
Warehouse notes payable
Reference rate for variable interest on the line of credit				30-day LIBOR
Basis points added to reference rate				1.40%
Agency Warehouse Facility #2 \| Agency Warehouse Facility
Warehouse notes payable
Uncommitted Amount		$ 300,000		$ 300,000
Number of lenders removed from credit facility. \| Lender		1
Uncommitted amount while temporary increase is outstanding		$ 0
Maturity date		Sep. 10, 2018
Agency Warehouse Facility #2 \| Agency Warehouse Facility \| LIBOR
Warehouse notes payable
Reference rate for variable interest on the line of credit				30-day LIBOR
Basis points added to reference rate				1.30%
Agency Warehouse Facility #2 \| Agency Warehouse Facility \| Temporary Commitment Increase
Warehouse notes payable
Maturity date		Feb. 28, 2018
Agency Warehouse Facility #3 \| LIBOR
Warehouse notes payable
Reference rate for variable interest on the line of credit			30-day LIBOR
Basis points added to reference rate			1.25%
Agency Warehouse Facility #3 \| Agency Warehouse Facility
Warehouse notes payable
Total Facility Capacity			$ 480,000
Maturity date			Apr. 30, 2018
Agency Warehouse Facility #3 \| Agency Warehouse Facility \| LIBOR
Warehouse notes payable
Reference rate for variable interest on the line of credit				30-day LIBOR
Basis points added to reference rate				1.25%
Agency Warehouse Facility #3 \| Agency Warehouse Facility \| Temporary Commitment Increase
Warehouse notes payable
Maturity date		Jan. 30, 2018
Agency Warehouse Facility #4 \| Agency Warehouse Facility
Warehouse notes payable
Maturity date	Oct. 05, 2018
Agency Warehouse Facility #4 \| Agency Warehouse Facility \| LIBOR
Warehouse notes payable
Reference rate for variable interest on the line of credit	30-day LIBOR			30-day LIBOR
Basis points added to reference rate	1.30%			1.40%
Agency Warehouse Facility #5 \| Agency Warehouse Facility \| LIBOR
Warehouse notes payable
Reference rate for variable interest on the line of credit				30-day LIBOR
Basis points added to reference rate				1.80%
Agency Warehouse Facility #6 \| Agency Warehouse Facility
Warehouse notes payable
Maturity date		Sep. 18, 2018
Agency Warehouse Facility #6 \| Agency Warehouse Facility \| LIBOR
Warehouse notes payable
Reference rate for variable interest on the line of credit				30-day LIBOR
Basis points added to reference rate				1.35%
Uncommitted Agency Warehouse Facility \| Agency Warehouse Facility \| LIBOR
Warehouse notes payable
Reference rate for variable interest on the line of credit				30-day LIBOR
Basis points added to reference rate				1.15%
Interim Warehouse Facility #1 \| Interim Warehouse Facility
Warehouse notes payable
Maturity date			Apr. 30, 2018
Interim Warehouse Facility #1 \| Interim Warehouse Facility \| LIBOR
Warehouse notes payable
Reference rate for variable interest on the line of credit				30-day LIBOR
Basis points added to reference rate				1.90%
Interim Warehouse Facility #2 \| Interim Warehouse Facility \| LIBOR
Warehouse notes payable
Reference rate for variable interest on the line of credit				30-day LIBOR
Basis points added to reference rate				2.00%
Interim Warehouse Facility #3 \| Interim Warehouse Facility
Warehouse notes payable
Maturity date			May 19, 2018
Interim Warehouse Facility #3 \| Interim Warehouse Facility \| LIBOR
Warehouse notes payable
Reference rate for variable interest on the line of credit				30-day LIBOR
Interim Warehouse Facility #3 \| Interim Warehouse Facility \| LIBOR \| Minimum
Warehouse notes payable
Basis points added to reference rate				2.00%
Interim Warehouse Facility #3 \| Interim Warehouse Facility \| LIBOR \| Maximum
Warehouse notes payable
Basis points added to reference rate				2.50%
Loans Held for Sale \| Agency Warehouse Facility
Warehouse notes payable
Committed Amount		$ 2,035,000		$ 2,035,000
Uncommitted Amount		1,750,000		1,750,000
Temporary Increase		2,466,000		2,466,000
Total Facility Capacity		6,251,000		6,251,000
Outstanding Balance		3,209,963		3,209,963
Loans Held for Sale \| Agency Warehouse Facility #1 \| Agency Warehouse Facility
Warehouse notes payable
Committed Amount		425,000		425,000
Total Facility Capacity		425,000		425,000
Outstanding Balance		190,054		190,054
Loans Held for Sale \| Agency Warehouse Facility #2 \| Agency Warehouse Facility
Warehouse notes payable
Committed Amount		500,000		500,000
Temporary Increase		2,066,000		2,066,000
Total Facility Capacity		2,566,000		2,566,000
Outstanding Balance		2,228,837		2,228,837
Loans Held for Sale \| Agency Warehouse Facility #3 \| Agency Warehouse Facility
Warehouse notes payable
Committed Amount		480,000		480,000
Temporary Increase		400,000		400,000
Total Facility Capacity		880,000		880,000
Outstanding Balance		424,714		424,714
Loans Held for Sale \| Agency Warehouse Facility #4 \| Agency Warehouse Facility
Warehouse notes payable
Committed Amount		350,000		350,000
Total Facility Capacity		350,000		350,000
Outstanding Balance		285,170		285,170
Loans Held for Sale \| Agency Warehouse Facility #5 \| Agency Warehouse Facility
Warehouse notes payable
Committed Amount		30,000		30,000
Total Facility Capacity		30,000		30,000
Outstanding Balance		5,797		5,797
Loans Held for Sale \| Agency Warehouse Facility #6 \| Agency Warehouse Facility
Warehouse notes payable
Committed Amount		250,000		250,000
Uncommitted Amount		250,000		250,000
Total Facility Capacity		500,000		500,000
Loans Held for Investment \| Interim Warehouse Facility
Warehouse notes payable
Committed Amount		360,000		360,000
Total Facility Capacity		360,000		360,000
Outstanding Balance		95,844		95,844
Loans Held for Investment \| Interim Warehouse Facility #1 \| Interim Warehouse Facility
Warehouse notes payable
Committed Amount		85,000		85,000
Total Facility Capacity		85,000		85,000
Outstanding Balance		43,440		43,440
Loans Held for Investment \| Interim Warehouse Facility #2 \| Interim Warehouse Facility
Warehouse notes payable
Committed Amount		200,000		200,000
Total Facility Capacity		200,000		200,000
Outstanding Balance		23,272		23,272
Loans Held for Investment \| Interim Warehouse Facility #3 \| Interim Warehouse Facility
Warehouse notes payable
Committed Amount		75,000		75,000
Total Facility Capacity		75,000		75,000
Outstanding Balance		29,132		29,132
National Banks \| Agency Warehouse Facility
Warehouse notes payable
Total Facility Capacity		4,800,000		4,800,000
National Banks \| Interim Warehouse Facility
Warehouse notes payable
Total Facility Capacity		400,000		400,000
Fannie Mae \| Loans Held for Sale \| Uncommitted Agency Warehouse Facility \| Agency Warehouse Facility
Warehouse notes payable
Uncommitted Amount		1,500,000		1,500,000
Total Facility Capacity		1,500,000		1,500,000
Outstanding Balance		$ 75,391		$ 75,391