Consolidated Statements of Shareholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock [Member]	Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Loss [Member]	Treasury Stock [Member]
Balance at period start (shares) at Dec. 31, 2014		31,299
Balance at period start at Dec. 31, 2014	$ 581,298	$ 313	$ 319,752	$ 406,145	$ (39,822)	$ (105,090)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued under employee plans	(1,974)		(6,297)			4,323
Tax benefit arising from common stock issued under employee plans	3,961		3,961
Stock-based compensation	7,499		7,499
Dividends on common stock	(22,137)			(22,137)
Comprehensive income (loss):
Foreign currency translation adjustments					(16,775)
Pension liability (net of income tax expense/benefit)					4,778
Cash flow hedging gain (loss) (net of income tax expense/benefit)					(2,075)
Net income	30,498			30,498
Comprehensive income	16,426
Balance at period end (shares) at Dec. 31, 2015		31,299
Balance at period end at Dec. 31, 2015	585,073	$ 313	324,915	414,506	(53,894)	(100,767)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued under employee plans	(869)		(4,217)			3,348
Tax benefit arising from common stock issued under employee plans	203		203
Stock-based compensation	8,375		8,375
Dividends on common stock	(22,238)			(22,238)
Comprehensive income (loss):
Foreign currency translation adjustments					(4,501)
Pension liability (net of income tax expense/benefit)					(476)
Cash flow hedging gain (loss) (net of income tax expense/benefit)					345
Net income	14,664			14,664
Comprehensive income	10,032
Balance at period end (shares) at Dec. 31, 2016		31,299
Balance at period end at Dec. 31, 2016	580,576	$ 313	329,276	406,932	(58,526)	(97,419)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued under employee plans	(217)		(3,953)			3,736
Stock-based compensation	8,472		8,472
Dividends on common stock	(22,334)			(22,334)
Comprehensive income (loss):
Foreign currency translation adjustments					13,879
Pension liability (net of income tax expense/benefit)					645
Cash flow hedging gain (loss) (net of income tax expense/benefit)					(5,076)
Net income	55,487			55,487
Comprehensive income	64,935
Balance at period end (shares) at Dec. 31, 2017		31,299
Balance at period end at Dec. 31, 2017	$ 631,432	$ 313	$ 333,795	$ 440,085	$ (49,078)	$ (93,683)