Employee Benefit Plans (Schedule of Plan's Pension Cost) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Service cost - benefits earned during the year	$ 3,733	$ 3,559
Interest cost on projected benefit obligations	3,621	3,505
Defined Benefit Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost - benefits earned during the year	3,733	3,559	$ 3,796
Interest cost on projected benefit obligations	3,621	3,505	3,178
Expected return on plan assets	(4,681)	(4,734)	(4,864)
Net amortization and deferral	1,382	1,259	1,542
Net periodic pension cost	$ 4,055	$ 3,589	$ 3,652