Retirement Benefit Plans (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Defined Benefit Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Pension expense (income)	$ (87)	$ (2)	$ (260)	$ (5)
Supplemental Employee Retirement Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Pension expense (income)	$ 250	$ 202	$ 749	$ 606
Supplemental Employee Retirement Plan | Minimum
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Retirement benefit, percentage			10.00%
Supplemental Employee Retirement Plan | Maximum
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Retirement benefit, percentage			20.00%