Litigation, Commitments, and Contingencies - Other Commitments (Detail) - Preferred Equity Investments	12 Months Ended
Dec. 31, 2015 USD ($)
Other Commitments
Investment commitments	$ 42,800,000
Investment commitment, funded	$ 0
Minimum
Other Commitments
Commitment funding period (in months)	18 months
Maximum
Other Commitments
Commitment funding period (in months)	36 months

Amount of other commitment funded as of the end of the reporting period 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.

No definition available.

Name:	wd_OtherCommitmentFundedAmount
Namespace Prefix:	wd_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant