Retirement Plans (Schedule of Benefit Obligation, Fair Value of Assets, and Funded Status of the Plans) (Details) - Pension Plan - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
United States
Change in benefit obligation
Benefit obligation at beginning of the year	$ 18,783	$ 18,241
Interest cost	622	684
Actuarial (gain) loss	(1,249)	775
Benefits paid	(1,439)	(917)
Benefit obligation at end of the year	16,717	18,783
Change in plan asset
Fair value of assets at beginning of year	14,892	14,180
Actual (loss) gain on plan asset	(985)	1,629
Benefits paid	(1,439)	(917)
Fair value of assets at end of year	12,468	14,892
Funded status at end of year	(4,249)	(3,891)
Amount recognized in the consolidated balance sheet consists of:
Other long-term liabilities	(4,249)	(3,891)
Amounts recognized in accumulated other comprehensive income consists of:
Net loss	4,406	3,913
United Kingdom
Change in benefit obligation
Benefit obligation at beginning of the year	8,335	8,104
Interest cost	194	236
Actuarial (gain) loss	(201)	(451)
Benefits paid	(292)	(322)
Foreign currency exchange rate changes	(475)	768
Benefit obligation at end of the year	7,750	8,335
Change in plan asset
Fair value of assets at beginning of year	6,904	5,826
Actual (loss) gain on plan asset	(144)	573
Employer contributions	271	276
Benefits paid	(292)	(322)
Foreign currency exchange rate changes	(392)	551
Fair value of assets at end of year	6,347	6,904
Funded status at end of year	(1,403)	(1,431)
Amount recognized in the consolidated balance sheet consists of:
Other long-term liabilities	(1,403)	(1,431)
Amounts recognized in accumulated other comprehensive income consists of:
Net loss	1,116	1,161
Prior service cost	208	39
Defined benefit plan, accumulated other income	$ 1,324	$ 1,200