Summary of Significant Accounting Policies - Additional Information (Details)	3 Months Ended
	Mar. 31, 2018 USD ($) Approach
Summary of Significant Accounting Policies [Line Items]
Estimating Real Property Value, Number of Approaches | Approach	3
Cash and Cash Equivalents, Maximum Initial Maturity	3 months
Interest Reserve Minimum Length	1 year
Interest Reserve Maximum Length	2 years
ASU 2014-09 [Member]
Summary of Significant Accounting Policies [Line Items]
Adoption of revenue standard, impact on recognition of interest income or late fees	$ 0
Real Estate Secured Loans [Member]
Summary of Significant Accounting Policies [Line Items]
Expected credit losses from investment	$ 0