No definition available.

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

- Definition

The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(1)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(2)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Number of performance targets defined under a share-based compensation award achieved at some level.

+ References

No definition available.

+ Details

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

- Definition

Number of performance targets defined under a share-based compensation award deemed probable of achievement at some level.

+ References

No definition available.

+ Details

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

- Definition

Value of shares authorized for issuance under share-based payment arrangement.

+ References

No definition available.

+ Details

Name:	wd_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesAuthorizedValue
Namespace Prefix:	wd_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	us-gaap_AwardTypeAxis=us-gaap_RestrictedStockUnitsRSUMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PlanNameAxis=wd_EquityIncentivePlan2020Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PlanNameAxis=wd_PerformanceSharePlanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_TitleOfIndividualAxis=wd_OfficersAndEmployeesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PlanNameAxis=wd_PerformanceSharePlan2017Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PlanNameAxis=wd_PerformanceSharePlan2018Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PlanNameAxis=wd_PerformanceSharePlan2019Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PlanNameAxis=wd_PerformanceSharePlan2020Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

SHARE-BASED PAYMENT - Plan Information (Details)	3 Months Ended	12 Months Ended
SHARE-BASED PAYMENT - Plan Information (Details)	Mar. 31, 2021 shares	Dec. 31, 2021 item shares	Dec. 31, 2020 item shares	Dec. 31, 2019 shares
Restricted Stock Units (RSUs)
Share-Based Payment
Granted (in shares)		263,845
Performance shares vested		55,483
2020 Equity Incentive Plan
Share-Based Payment
Stock authorized for issuance		10,500,000
Number of shares remaining available for grant		1,700,000
PSP \| Restricted Stock Units (RSUs) \| Officers And Employees
Share-Based Payment
Granted (in shares)		300,000	300,000	300,000
2017 PSP
Share-Based Payment
Number of performance targets achieved at some level \| item			3
Number of performance targets deemed probable of achievement at some level \| item			3
2017 PSP \| Restricted Stock Units (RSUs)
Share-Based Payment
Performance shares vested	100,000
2018 PSP
Share-Based Payment
Number of performance targets deemed probable of achievement at some level \| item			2
2019 PSP
Share-Based Payment
Number of performance targets deemed probable of achievement at some level \| item		3	3
2020 PSP
Share-Based Payment
Number of performance targets deemed probable of achievement at some level \| item		3