Employee Pension Plans (Components of Net Periodic Benefit Cost) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Summary of net periodic benefit cost
Interest cost	$ 883	$ 975	$ 2,649	$ 2,925
Expected return on plan assets	(1,077)	(1,088)	(3,231)	(3,264)
Amortization of net loss	513	456	1,539	1,368
Other	213	213	639	639
Net periodic benefit cost	532	$ 556	1,596	1,668
Company contribution			2,100	$ 2,000
Expected contributions remainder of current fiscal year	$ 700		$ 700