Derivative Instruments Derivative gain loss (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Interest Rate Swap No. 2 [Member]
Derivative Instruments, Gain (Loss) [Line Items]
5 yr Interest Rate Swap	$ 316	$ 388
Interest Rate Derivative Liabilities, at Fair Value	211	353
Interest Rate Swap No. 1 [Member]
Derivative Instruments, Gain (Loss) [Line Items]
5 yr Interest Rate Swap	513	583
Interest Rate Derivative Liabilities, at Fair Value	835	1,229
Interest Rate Swap [Domain]
Derivative Instruments, Gain (Loss) [Line Items]
5 yr Interest Rate Swap	829	971
Interest Rate Derivative Liabilities, at Fair Value	$ 1,046	1,582
Fair Value, Inputs, Level 2 [Member] | Interest Rate Swap No. 2 [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Term of Contract	5 years
Interest Rate Derivative Liabilities, at Fair Value	$ 211	353
Fair Value, Inputs, Level 2 [Member] | Interest Rate Swap No. 1 [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Term of Contract	10 years
Interest Rate Derivative Liabilities, at Fair Value	$ 835	$ 1,229