Derivative Instruments (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Effects of derivative instruments
Amount of Gain Recognized in OCI on Derivatives (Effective Portion)	$ (112)	$ 967	$ 323	$ 526
Cash Flow Hedging
Effects of derivative instruments
Amount of Gain Recognized in OCI on Derivatives (Effective Portion)	(338)		(3)
Amount of Loss (Gain) Reclassified from Accumulated OCI into Income (Effective Portion)	174		400
Cash Flow Hedging | Interest expense Member
Effects of derivative instruments
Amount of Loss (Gain) Reclassified from Accumulated OCI into Income (Effective Portion)	174		400
Cash Flow Hedging | Interest rate contracts | Interest expense Member
Effects of derivative instruments
Amount of Gain Recognized in OCI on Derivatives (Effective Portion)	$ (338)		$ (3)