Real Estate and Lending Activities - Concentrations of Credit Risk - Additional Information (Detail) - Pro Forma [Member] - Total Gross Assets [Member] - Customer Concentration Risk [Member]	Sep. 30, 2017 Investment
Business Acquisition [Line Items]
Number of investment in property	0
Maximum percentage of entity's gross assets invested on single property	3.80%

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.

No definition available.

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