Related Party Transactions - Summary of Fees and Expenses Accrued under Advisory Agreement (Parenthetical) (Detail) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Base Management Fees [Member] \| Fs Real Estate Advisor [Member]
Related Party Transaction [Line Items]
Fees and expenses accrued	$ 23	$ 0
Management Fee Payable	47
Performance Fees [Member] \| Fs Real Estate Advisor [Member]
Related Party Transaction [Line Items]
Fees and expenses accrued	20	0
Performance Fee Payable	24
Administrative Services Expenses [Member] \| Related Party For Services Rendered [Member]
Related Party Transaction [Line Items]
Fees and expenses accrued	$ 1,826	$ 196

Direct costs arising from transactions with related parties who are not affiliates or joint Ventures. These costs are categorized as cost of goods sold.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.2)
-URI http://asc.fasb.org/extlink&oid=115205541&loc=SL114868664-224227

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(k)(1))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

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