Employee Benefit Plans (Schedule of Net Funded Status) (Details) - USD ($) $ in Thousands		Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Change In Benefit Obligation [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets		$ 103,236	$ 84,770
Defined Benefit Plan, Benefit Obligation		172,143	161,955
Defined Benefit Plan, Funded Status of Plan, Total		(68,907)	(77,185)
Qualified Plan [Member]
Defined Benefit Plan Change In Benefit Obligation [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets		103,236	84,770
Defined Benefit Plan, Benefit Obligation		107,072	96,418
Defined Benefit Plan, Funded Status of Plan, Total		(3,836)	(11,648)
Nonqualified Plan [Member]
Defined Benefit Plan Change In Benefit Obligation [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	0	0
Defined Benefit Plan, Benefit Obligation	[1]	65,071	65,537
Defined Benefit Plan, Funded Status of Plan, Total	[1]	$ (65,071)	$ (65,537)

[1] For non-qualified plans, there are no required funding levels.