Pension - Periodic Benefit Cost (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Components of net periodic benefit cost:
Interest cost	$ 14	$ 14
Service cost	9	9
Expected return on plan assets	(20)	(19)
Amortization of prior service costs	2
Amortization of actuarial loss	26	31
Net periodic benefit cost	$ 31	$ 35