Mortgage Notes Receivable - Aggregate Principal Payments (Details) - Mortgage notes receivable [Member] $ in Thousands	3 Months Ended
	Mar. 31, 2018 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Due within one year	$ 945
Due after one year through five years	4,503
Due after five years through 10 years	7,105
Due after 10 years	13,494
Total	26,047
Interest scheduled to be capitalized	$ 3,800