Mortgage Notes Receivable - Aggregate Principal Payments (Details) - Mortgage notes receivable [Member] $ in Thousands	9 Months Ended
	Sep. 30, 2017 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Due within one year	$ 915
Due after one year through five years	4,341
Due after five years through 10 years	7,071
Due after 10 years	14,175
Total	26,502
Interest scheduled to be capitalized	$ 3,800