Derivative Instruments and Hedging Activities Derivative Gain (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Derivative Instruments, Gain (Loss) [Line Items]
Fair value of interest rate derivatives	$ 138		$ (194)
Interest Rate Swap No. 2 [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, term of contract	5 years		5 years
Fair value of interest rate derivatives	$ 78		$ 135
Unrealized gain (loss) on interest rate cash flow hedges		$ 56
Interest Rate Swap No. 1 [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, term of contract	10 years		10 years
Fair value of interest rate derivatives	$ (434)		$ (70)
Unrealized gain (loss) on interest rate cash flow hedges	(49)	8
Interest Rate Swap [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Fair value of interest rate derivatives	(356)		$ 65
Unrealized gain (loss) on interest rate cash flow hedges	$ (49)	$ 64