Employee Benefit Plans (Schedule of SERP's Pension Cost) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Service cost - benefits earned during the year	$ 3,559	$ 3,795
Interest cost on projected benefit obligations	3,505	3,178
Supplemental Executive Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost - benefits earned during the year	133	140	$ 136
Interest cost on projected benefit obligations	367	348	377
Net amortization and deferral	295	654	431
Net periodic pension cost	$ 795	$ 1,142	$ 944