Consolidated Statement of Shareholders' Equity - USD ($)	Total	Common Stock	Additional Paid-in- Capital	Retained Earnings	Accumulated Other Comprehensive Earnings	Treasury Stock	Class B Common Shares
Beginning Balance at Dec. 31, 2016	$ 422,387,000	$ 8,974,000	$ 266,151,000	$ 266,144,000	$ (19,335,000)	$ (99,730,000)	$ 183,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options	(2,611,000)	(48,000)	(2,628,000)			(65,000)
Stock-based compensation expense	1,834,000		1,834,000
Non-qualified stock option expense	865,000		865,000
Restricted stock awards	3,437,000	101,000	4,547,000			(1,211,000)
Conversion from Class B to Common Stock	0	(181,000)					(181,000)
Net loss	(76,541,000)			(76,541,000)
Foreign currency translation adjustments	54,591,000
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax, Portion Attributable to Parent	54,591,000
Unrealized gain on cash flow hedges	(1,982,000)				(1,982,000)
Defined benefit plans:
Amortization of prior service costs and unrecognized losses and credits	3,596,000				3,596,000
Comprehensive Loss	(20,336,000)
Dividends	(1,604,000)
Ending Balance at Dec. 31, 2017	423,294,000	9,304,000	290,125,000	187,999,000	36,870,000	(101,006,000)	2,000
Defined benefit plans:
Proceeds from Issuance of Warrants	14,100,000
Adjustments to Additional Paid in Capital, Warrant Issued	14,100,000		14,100,000
Payments of Ordinary Dividends, Common Stock	1,604,000
Exercise of stock options	(1,707,000)	(46,000)	(2,580,000)			(919,000)
Stock-based compensation expense	777,000		777,000
Non-qualified stock option expense	201,000		201,000
Restricted stock awards	2,797,000	69,000	4,236,000			(1,508,000)
Net loss	(43,922,000)			(43,922,000)
Foreign currency translation adjustments	(30,858,000)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax, Portion Attributable to Parent	(30,858,000)
Unrealized gain on cash flow hedges	1,832,000				1,832,000
Amortization of prior service costs and unrecognized losses and credits	4,949,000				4,949,000
Comprehensive Loss	(67,999,000)
Dividends	(1,630,000)
Ending Balance at Dec. 31, 2018	359,147,000	9,419,000	297,919,000	142,447,000	12,793,000	(103,433,000)	2,000
Defined benefit plans:
Proceeds from Issuance of Warrants	0
Payments of Ordinary Dividends, Common Stock	1,630,000
Stock-based compensation expense	4,051,000	29,000	4,370,000			(348,000)
Non-qualified stock option expense	1,939,000		1,939,000
Restricted stock awards	4,226,000	140,000	4,632,000			(546,000)
Net loss	(53,327,000)			(53,327,000)
Foreign currency translation adjustments	(8,499,000)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax, Portion Attributable to Parent	(8,499,000)
Unrealized gain on cash flow hedges	(570,000)				(570,000)
Amortization of prior service costs and unrecognized losses and credits	(596,000)				(596,000)
Comprehensive Loss	(62,992,000)
Dividends	(1,645,000)
Ending Balance at Dec. 31, 2019	308,516,000	$ 9,588,000	312,650,000	$ 87,475,000	$ 3,128,000	$ (104,327,000)	$ 2,000
Defined benefit plans:
Convertible Debt Derivative Adjustments	(220,000)		(220,000)
Exchange of Convertible Notes	4,010,000		$ 4,010,000
Proceeds from Issuance of Warrants	0
Payments of Ordinary Dividends, Common Stock	$ 1,645,000