Schedule of Net Periodic Pension Benefit Costs (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Defined Benefit Plan [Abstract]
Service cost	$ 1,008	$ 994	$ 3,025	$ 2,846
Interest cost	567	568	1,767	1,628
Expected return on plan assets	(160)	(152)	(510)	(445)
Amortization of actuarial net loss	383	431	1,178	1,225
Amortization of unrecognized prior service costs	16	16	50	46
Net periodic benefit cost	$ 1,814	$ 1,857	$ 5,510	$ 5,300