Risk Management and Use of Derivative Financial Instruments - Narratives (Details) - USD ($)	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Derivative
Cash collateral posted	$ 0	$ 0
Derivative instrument remaining maturity period	74 months
Collateral received	$ 0
Total credit exposure	3,400,000
Derivative in net liability position	1,600,000	4,400,000
Termination value of assets	1,600,000	$ 4,500,000
Individual Counterparty
Derivative
Total credit exposure	1,900,000
Interest expense
Derivative
Estimated amount of derivative loss to be reclassified to interest expense in the next 12 months	200,000
Other income
Derivative
Estimated amount of derivative loss to be reclassified to interest expense in the next 12 months	$ 800,000