Derivative Instruments - Cash flow hedges (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Effects of derivative instruments
Amount of Gain Recognized in OCI on Derivatives (Effective Portion)	$ (237,000)	$ 1,957,000	$ (799,000)
Parent Company [Member]
Effects of derivative instruments
Amount of Gain Recognized in OCI on Derivatives (Effective Portion)	(237,000)	1,957,000	(799,000)
Cash Flow Hedging
Effects of derivative instruments
Amount of Gain Recognized in OCI on Derivatives (Effective Portion)	533,000	1,061,000	69,000
Amount of Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	359,000	(621,000)	(25,000)
Significant ineffectiveness on held hedges	0
Cash Flow Hedging | Interest rate contract | Interest expense [Member]
Effects of derivative instruments
Amount of Gain Recognized in OCI on Derivatives (Effective Portion)	533,000	1,061,000	69,000
Amount of Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	$ 359,000	$ (621,000)	$ (25,000)