Employee Benefit Plans (Schedule of Periodic Costs For Employee Retirement Benefit Plans) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Pension Benefit Plan [Member]
Periodic costs for employee retirement benefit plans
Service Cost	$ 2,308	$ 2,558	$ 1,894
Interest Cost	3,046	2,894	2,682
Expected Return on Plan Assets	(4,014)	(3,919)	(3,534)
Amortization of Net Actuarial Loss	1,426	1,645	416
Amortization of Prior Service Cost/(Credit)			2
Net Periodic Benefit Cost	2,766	3,178	1,460
Other Benefits Plan [Member]
Periodic costs for employee retirement benefit plans
Service Cost	1,099	1,373	1,032
Interest Cost	1,952	1,921	1,792
Expected Return on Plan Assets	(2,213)	(2,107)	(1,937)
Amortization of Net Actuarial Loss	1,773	2,261	1,413
Amortization of Prior Service Cost/(Credit)	(1,728)	(1,728)	(1,728)
Net Periodic Benefit Cost	$ 883	$ 1,720	$ 572