Consolidated Condensed Statements of Shareholders' Equity (Unaudited) - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Loss	Treasury Stock
Balance at period start (shares) at Dec. 31, 2018		31,299
Balance at period start at Dec. 31, 2018	$ 662,270	$ 313	$ 341,738	$ 464,851	$ (55,737)	$ (88,895)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued under employee plans	1,748		(769)			2,517
Stock-based compensation	2,703		2,703
Dividends on common stock ($0.20 per share)	(5,643)			(5,643)
Convertible notes discount (net of income tax expense)	39,145		39,145
Convertible notes hedge, (net of income tax benefit)	(38,829)		(38,829)
Issuance of warrants	30,567		30,567
Comprehensive income (loss):
Foreign currency translation adjustments					(578)
Pension liability, net of income tax					547
Cash flow hedging gain (loss), net of income tax					106
Net income (loss)				1,021
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest	1,096
Balance at period end (shares) at Mar. 31, 2019		31,299
Balance at period end at Mar. 31, 2019	693,057	$ 313	374,555	460,229	(55,662)	(86,378)
Balance at period start (shares) at Dec. 31, 2018		31,299
Balance at period start at Dec. 31, 2018	662,270	$ 313	341,738	464,851	(55,737)	(88,895)
Comprehensive income (loss):
Foreign currency translation adjustments	(4,240)
Pension liability, net of income tax	1,639
Cash flow hedging gain (loss), net of income tax	423
Net income (loss)	13,686
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest	11,508
Balance at period end (shares) at Sep. 30, 2019		31,299
Balance at period end at Sep. 30, 2019	700,922	$ 313	379,137	461,564	(57,915)	(82,177)
Balance at period start (shares) at Mar. 31, 2019		31,299
Balance at period start at Mar. 31, 2019	693,057	$ 313	374,555	460,229	(55,662)	(86,378)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued under employee plans	750		(1,144)			1,894
Stock-based compensation	3,108		3,108
Dividends on common stock ($0.20 per share)	(5,657)			(5,657)
Comprehensive income (loss):
Foreign currency translation adjustments					1,108
Pension liability, net of income tax					546
Cash flow hedging gain (loss), net of income tax					(1,598)
Net income (loss)				5,695
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest	5,751
Balance at period end (shares) at Jun. 30, 2019		31,299
Balance at period end at Jun. 30, 2019	697,009	$ 313	376,519	460,267	(55,606)	(84,484)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued under employee plans	1,917		(390)			2,307
Stock-based compensation	3,008		3,008
Dividends on common stock ($0.20 per share)	(5,673)			(5,673)
Comprehensive income (loss):
Foreign currency translation adjustments	(4,770)				(4,770)
Pension liability, net of income tax	546				546
Cash flow hedging gain (loss), net of income tax	1,915				1,915
Net income (loss)	6,970			6,970
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest	4,661
Balance at period end (shares) at Sep. 30, 2019		31,299
Balance at period end at Sep. 30, 2019	700,922	$ 313	379,137	461,564	(57,915)	(82,177)
Balance at period start (shares) at Dec. 31, 2019		31,299
Balance at period start at Dec. 31, 2019	710,467	$ 313	379,324	470,844	(59,277)	(80,737)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued under employee plans	(5,040)		(7,736)			2,696
Stock-based compensation	3,032		3,032
Dividends on common stock ($0.20 per share)	(5,703)			(5,703)
Comprehensive income (loss):
Foreign currency translation adjustments					(9,988)
Pension liability, net of income tax					535
Cash flow hedging gain (loss), net of income tax					2,405
Net income (loss)				5,927
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest	(1,121)
Balance at period end (shares) at Mar. 31, 2020		31,299
Balance at period end at Mar. 31, 2020	701,635	$ 313	374,620	471,068	(66,325)	(78,041)
Balance at period start (shares) at Dec. 31, 2019		31,299
Balance at period start at Dec. 31, 2019	710,467	$ 313	379,324	470,844	(59,277)	(80,737)
Comprehensive income (loss):
Foreign currency translation adjustments	(790)
Pension liability, net of income tax	1,605
Cash flow hedging gain (loss), net of income tax	(3,050)
Net income (loss)	(14,623)
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest	(16,858)
Balance at period end (shares) at Sep. 30, 2020		31,299
Balance at period end at Sep. 30, 2020	683,141	$ 313	381,119	439,086	(61,512)	(75,865)
Balance at period start (shares) at Mar. 31, 2020		31,299
Balance at period start at Mar. 31, 2020	701,635	$ 313	374,620	471,068	(66,325)	(78,041)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued under employee plans	133		(1,150)			1,283
Stock-based compensation	3,555		3,555
Dividends on common stock ($0.20 per share)	(5,712)			(5,712)
Comprehensive income (loss):
Foreign currency translation adjustments					4,581
Pension liability, net of income tax					535
Cash flow hedging gain (loss), net of income tax					(2,429)
Net income (loss)				(27,400)
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest	(24,713)
Balance at period end (shares) at Jun. 30, 2020		31,299
Balance at period end at Jun. 30, 2020	674,898	$ 313	377,025	437,956	(63,638)	(76,758)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued under employee plans	1,455		562			893
Stock-based compensation	3,532		3,532
Dividends on common stock ($0.20 per share)	(5,720)			(5,720)
Comprehensive income (loss):
Foreign currency translation adjustments	4,617				4,617
Pension liability, net of income tax	535				535
Cash flow hedging gain (loss), net of income tax	(3,026)				(3,026)
Net income (loss)	6,850			6,850
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest	8,976
Balance at period end (shares) at Sep. 30, 2020		31,299
Balance at period end at Sep. 30, 2020	$ 683,141	$ 313	$ 381,119	$ 439,086	$ (61,512)	$ (75,865)