Derivatives and Hedging Activities - Narrative (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($) derivative	Dec. 31, 2016 USD ($) derivative
Derivative [Line Items]
Derivative assets	$ 627	$ 199
Loans Payable [Member] | Credit Facility [Member]
Derivative [Line Items]
Gain (Loss) reclassified from AOCI	1,100
Cash Flow Hedging [Member]
Derivative [Line Items]
Notional amount	$ 27,800
Number of instruments held | derivative	1
Interest Rate Swap [Member]
Derivative [Line Items]
Amount of gain (loss) related to change in fair value and other ineffectiveness	$ 300	(300)
Aggregate termination value had provisions been breached	$ 600
Interest Rate Swap [Member] | Loans Payable [Member] | Credit Facility [Member]
Derivative [Line Items]
Number of interest rate swaps | derivative	6
Interest Rate Swap [Member] | Cash Flow Hedging [Member]
Derivative [Line Items]
Gain (Loss) in earnings related to ineffective portion	$ 1,600	$ 2,500
Interest Rate Swap [Member] | Cash Flow Hedging [Member] | Interest Expense [Member]
Derivative [Line Items]
Gain (Loss) reclassified from AOCI	(200)
Reclassified from AOCI interest expense in relation to previously settled interest rate derivatives	800
Derivative loss to be reclassified during next 12 months	$ 300
Interest Rate Swap [Member] | Designated as Hedging Instrument [Member] | Cash Flow Hedging [Member]
Derivative [Line Items]
Number of interest rate swaps | derivative	0	14
Number of derivative instruments associated with loans | derivative	13
Notional amount	$ 0	$ 690,816
Thirteen Interest Rate Swaps [Member] | Designated as Hedging Instrument [Member] | Cash Flow Hedging [Member]
Derivative [Line Items]
Notional amount	$ 662,400