Mortgage Notes Receivable - Narrative (Details) - Mortgage notes receivable [Member]	3 Months Ended
	Mar. 31, 2018 loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of mortgage notes receivable	8
Weighted-average interest rate	6.20%
Weighted-average years to maturity	12 years 4 months 24 days
Number of mortgage notes with capitalized principal and interest	1