Derivative and Hedging Activities (Details) - Location of Gain or Loss on Interest Rate Derivatives Designated as Cash Flow Hedges - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Amount of gain recognized in OCI on derivatives	$ 3,665	$ 541	$ 0
Amount of loss reclassified from accumulated OCI into interest	$ 1,920	$ 2,473	$ 2,139