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, 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):
Cash flow hedging gain, net of income tax	2,405				2,405
Pension liability, net of income tax	535				535
Foreign currency translation adjustments	(9,988)				(9,988)
Net income	5,927			5,927
Comprehensive income (loss)	(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, 2020		31,299
Balance at period start at Dec. 31, 2020	709,038	$ 313	382,628	457,417	(63,681)	(67,639)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued under employee plans	8,215		2,944			5,271
Stock-based compensation	3,387		3,387
Dividends on common stock ($0.20 per share)	(5,813)			(5,813)
Comprehensive income (loss):
Cash flow hedging gain, net of income tax	3,926				3,926
Pension liability, net of income tax	631				631
Foreign currency translation adjustments	(3,674)				(3,674)
Net income	9,860			9,860
Comprehensive income (loss)	10,743
Balance at period end (shares) at Mar. 31, 2021		31,299
Balance at period end at Mar. 31, 2021	$ 725,570	$ 313	$ 388,959	$ 461,464	$ (62,798)	$ (62,368)