Retirement Plans (Schedule of Fair Value, Assets Measured on Recurring Basis) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets, excluding cash and cash equivalents	$ 10,742	$ 10,091
Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets, excluding cash and cash equivalents	3,586	3,438
Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets, excluding cash and cash equivalents	7,156	6,653
Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets, excluding cash and cash equivalents	7,156	6,653
Fair Value, Inputs, Level 1 [Member] | Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets, excluding cash and cash equivalents	7,156	6,653
Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets, excluding cash and cash equivalents	3,586	3,438
Fair Value, Inputs, Level 2 [Member] | Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets, excluding cash and cash equivalents	$ 3,586	$ 3,438