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

No definition available.

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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

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

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=64930739&loc=d3e28878-108400

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28551-108399

+ Details

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

- 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

- Definition

Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of the required periodic payments including both interest and principal payments.

+ 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 942
-SubTopic 470
-Section 50
-Paragraph 3
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=75038535&loc=d3e64711-112823

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Indebtedness divided by net capital.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

- Definition

Asset coverage ratio.

+ References

No definition available.

+ Details

Name:	wd_AssetCoverageRatio
Namespace Prefix:	wd_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

- Definition

Debt discount percentage.

+ References

No definition available.

+ Details

Name:	wd_DebtDiscountPercentage
Namespace Prefix:	wd_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Minimum interest rate if an event of default has occurred as defined under the terms debt instrument.

+ References

No definition available.

+ Details

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Namespace Prefix:	wd_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of required mandatory prepayment under terms of the debt instrument.

+ References

No definition available.

+ Details

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

- Definition

Maximum amount of all incremental term loans.

+ References

No definition available.

+ Details

Name:	wd_DebtInstrumentPotentialIncreaseInFaceAmount
Namespace Prefix:	wd_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Interest coverage ratio.

+ References

No definition available.

+ Details

Name:	wd_InterestCoverageRatio
Namespace Prefix:	wd_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of additional term loans.

+ References

No definition available.

+ Details

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

- Details

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- Details

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- Details

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- Details

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- Details

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DEBT - Notes Payable - Terms (Detail) $ in Millions		1 Months Ended	3 Months Ended				12 Months Ended
DEBT - Notes Payable - Terms (Detail) $ in Millions	Dec. 20, 2013 USD ($) loan	Apr. 30, 2015 USD ($)	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2015 USD ($)	Mar. 31, 2015 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016
LIBOR
Debt
Reference rate							30-day LIBOR	30-day LIBOR
Term Loan Agreement
Debt
Amount of loan agreement	$ 175.0
Maximum amount of all incremental term loans	$ 60.0
Discount on issue of term loan (as a percent)	1.00%
Quarterly equal installments					$ 0.3	$ 0.4	$ 0.3
Mandatory prepayment		$ 3.6
Debt instrument maturity date							Dec. 20, 2020
Minimum LIBOR rate, default terms (as a percent)							1.00%
Term Loan Agreement \| Base Rate
Debt
Basis points added to reference rate				3.25%
Term Loan Agreement \| Prime rate (Base)
Debt
Reference rate							prime rate
Term Loan Agreement \| Federal funds rate (Base)
Debt
Reference rate							Federal funds rate
Basis points added to reference rate							0.50%
Term Loan Agreement \| 30-day LIBOR (Base)
Debt
Reference rate							one month LIBOR
Basis points added to reference rate							1.00%
Term Loan Agreement \| LIBOR
Debt
Basis points added to reference rate				4.25%
Amendment to Term Loan \| Base Rate
Debt
Basis points added to reference rate			2.00%
Amendment to Term Loan \| LIBOR
Debt
Basis points added to reference rate			3.00%
Minimum \| Term Loan Agreement
Debt
Consolidated Corporate Leverage Ratio			4.25				4.25
Consolidated Corporate Interest Coverage Ratio							2.75
Asset Coverage Ratio							1.50
Maximum \| Term Loan Agreement
Debt
Number of additional term loans \| loan	3