Employee Pension Plans (Components of Net Periodic Benefit Cost) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Summary of net periodic benefit cost
Interest cost	$ 883	$ 975	$ 1,766	$ 1,950
Expected return on plan assets	(1,077)	(1,088)	(2,154)	(2,176)
Amortization of net loss	513	456	1,026	912
Other	213	213	426	426
Net periodic benefit cost	532	$ 556	1,064	1,112
Company contribution			1,400	$ 1,400
Expected contributions remainder of current fiscal year	$ 1,300		$ 1,300