Employee Benefit Plans (Schedule of Expected Future Benefit Payments) (Details) $ in Thousands	Dec. 31, 2017 USD ($)
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Estimated Future Benefit Payments [Abstract]
Defined Benefit Plan, Expected Future Benefit Payments in Year One	$ 9,315
Defined Benefit Plan, Expected Future Benefit Payments in Year Two	9,765
Defined Benefit Plan, Expected Future Benefit Payment, Year Three	10,885
Defined Benefit Plan, Expected Future Benefit Payment, Year Four	11,102
Defined Benefit Plan, Expected Future Benefit Payment, Year Five	13,184
Defined Benefit Plan, Expected Future Benefit Payments in Five Fiscal Years Thereafter	69,285
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan, Estimated Future Benefit Payments [Abstract]
Defined Benefit Plan, Expected Future Benefit Payments in Year One	1,238
Defined Benefit Plan, Expected Future Benefit Payments in Year Two	1,495
Defined Benefit Plan, Expected Future Benefit Payment, Year Three	1,842
Defined Benefit Plan, Expected Future Benefit Payment, Year Four	2,188
Defined Benefit Plan, Expected Future Benefit Payment, Year Five	2,521
Defined Benefit Plan, Expected Future Benefit Payments in Five Fiscal Years Thereafter	$ 18,205