Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning Balance	[1]	$ (2,700)
Other comprehensive income (loss) before reclassifications	[1]	(1,120)	$ 504
Amounts reclassified from accumulated other comprehensive income (loss)	[1]	(168)	0
Other comprehensive income (loss)	[1]	(1,288)	504
Ending balance	[1]	(3,988)	(11,964)
Foreign Currency Translation Adjustment
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning Balance	[1]	(7,716)	(11,002)
Other comprehensive income (loss) before reclassifications	[1]	(1,150)	514
Amounts reclassified from accumulated other comprehensive income (loss)	[1]	0	0
Other comprehensive income (loss)		(1,150)	514	[1]
Ending balance	[1]	(8,866)	(10,488)
Investment in Convertible Preferred and Debt Securities
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning Balance		344
Other comprehensive income (loss) before reclassifications		(87)
Amounts reclassified from accumulated other comprehensive income (loss)		0
Other comprehensive income (loss)		(87)
Ending balance		257
Defined Benefit Plan Items
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning Balance	[1]	4,672	(1,466)
Other comprehensive income (loss) before reclassifications	[1]	117	(10)
Amounts reclassified from accumulated other comprehensive income (loss)	[1]	(168)	0
Other comprehensive income (loss)		(51)	(10)	[1]
Ending balance	[1]	$ 4,621	$ (1,476)

[1] All amounts are net of tax. Amounts in parentheses indicate debits