Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands		3 Months Ended			9 Months Ended
		Sep. 30, 2017	Sep. 30, 2016		Sep. 30, 2017		Sep. 30, 2016
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning Balance	[1]	$ (11,993)	$ (17,094)		$ (12,468)		$ (20,939)
Other comprehensive income (loss) before reclassifications	[1]	2,453	(155)		2,928		3,926
Amounts reclassified from accumulated other comprehensive income (loss)	[1]	(142)	(56)		(142)		(292)
Other comprehensive income (loss)	[1]	2,311	(211)		2,786		3,634
Ending balance	[1]	(9,682)	(17,305)		(9,682)		(17,305)
Losses on Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning Balance	[1]		9				(111)
Other comprehensive income (loss) before reclassifications	[1]		0				120
Amounts reclassified from accumulated other comprehensive income (loss)	[1]		0				0
Other comprehensive income (loss)	[1]		0				120
Ending balance	[1]		9				9
Foreign Currency Translation Adjustment
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning Balance	[1]	(9,529)	(9,484)		(11,002)		(12,041)
Other comprehensive income (loss) before reclassifications	[1]	2,201	(298)		3,674		2,259
Amounts reclassified from accumulated other comprehensive income (loss)	[1]	0	0		0		0
Other comprehensive income (loss)		2,201	(298)	[1]	3,674		2,259	[1]
Ending balance	[1]	(7,328)	(9,782)		(7,328)		(9,782)
Investment in Convertible Preferred and Debt Securities
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning Balance		0			0	[1]	126	[1]
Other comprehensive income (loss) before reclassifications		211			211	[1]	0	[1]
Amounts reclassified from accumulated other comprehensive income (loss)		0			0		(126)	[1]
Other comprehensive income (loss)		211			211	[1]	(126)	[1]
Ending balance	[1]	211	0		211		0
Defined Benefit Plan Items
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning Balance	[1]	(2,464)	(7,619)		(1,466)		(8,913)
Other comprehensive income (loss) before reclassifications	[1]	41	143		(957)		1,547
Amounts reclassified from accumulated other comprehensive income (loss)	[1]	(142)	(56)		(142)		(166)
Other comprehensive income (loss)		(101)	87	[1]	(1,099)		1,381	[1]
Ending balance	[1]	$ (2,565)	$ (7,532)		$ (2,565)		$ (7,532)

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