Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($) |
9 Months Ended | ||
|---|---|---|---|
Sep. 30, 2017 |
Apr. 30, 2017 |
Jun. 30, 2015 |
|
| Accounts, Notes, Loans and Financing Receivable [Line Items] | |||
| Joint venture capital contribution percentage | 85.00% | ||
| Income accrual, description | Income accrual is generally suspended for loans at the earlier of the date at which payments become 90 days past due or when, in the opinion of our Manager, recovery of income and principal becomes doubtful. | ||
| Cash and cash equivalents, description | Cash and cash equivalents represent cash held in banks, cash on hand, and liquid investments with original maturities of three months or less. | ||
| Expected loss | $ 0 | ||
| Provision for loan losses | $ 0 | ||
| Walker and Dunlop [Member] | |||
| Accounts, Notes, Loans and Financing Receivable [Line Items] | |||
| Joint venture capital contribution percentage | 15.00% | ||
| General Electrical Capital Corporation [Member] | |||
| Accounts, Notes, Loans and Financing Receivable [Line Items] | |||
| Purchase price of Loan Portfolio | $ 4,700,000,000 |