Condensed Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Treasury Stock
Balance at Dec. 31, 2017	$ 884,778	$ 473	$ 260,157	$ 676,644	$ (12,496)	$ (40,000)
Balance (in shares) at Dec. 31, 2017		46,745
Increase (Decrease) in Stockholders' Equity
Net income	113,876			113,876
Translation adjustment, net of tax	(10,533)				(10,533)
Options exercised	695	$ 0	695
Options exercised (in shares)		23
Stock-based compensation	7,939		7,939
Shares issued from release of Restricted Stock Units	(5,128)	$ 2	(5,130)
Shares issued from release of Restricted Stock Units (in shares)		177
Repurchase of common stock	(49,490)		10,000			(59,490)
Repurchase of common stock (in shares)		(985)
Retirement of common stock	0	$ (13)		(74,986)		74,999
Cash dividends declared on common stock	(29,974)			(29,974)
Common stock issued	465		465
Common stock issued (in shares)		8
Balance at Sep. 30, 2018	913,419	$ 462	274,126	686,351	(23,029)	(24,491)
Balance (in shares) at Sep. 30, 2018		45,968
Balance at Dec. 31, 2017	884,778	$ 473	260,157	676,644	(12,496)	(40,000)
Balance (in shares) at Dec. 31, 2017		46,745
Increase (Decrease) in Stockholders' Equity
Net income	12,757			12,757
Translation adjustment, net of tax	(2,378)				(2,378)
Pension adjustment, net of tax	376				376
Stock-based compensation	2,395		2,395
Adoption of new accounting standards				(381)	381
Shares issued from release of Restricted Stock Units	(17)	$ 0	(17)
Shares issued from release of Restricted Stock Units (in shares)		0
Repurchase of common stock	(61,050)		0			(61,050)
Repurchase of common stock (in shares)		(970)
Retirement of common stock	0	$ (9)		(60,532)		60,541
Cash dividends declared on common stock	(9,988)			(9,988)
Balance at Dec. 31, 2018	855,514	$ 453	276,504	628,207	(24,650)	(25,000)
Balance (in shares) at Dec. 31, 2018		44,998
Increase (Decrease) in Stockholders' Equity
Net income	105,925			105,925
Translation adjustment, net of tax	5,825				(5,825)
Pension adjustment, net of tax	462				462
Stock-based compensation	8,007		8,007
Shares issued from release of Restricted Stock Units	(5,903)	$ 2	(5,905)
Shares issued from release of Restricted Stock Units (in shares)		178
Repurchase of common stock	(51,437)		0			(51,437)
Repurchase of common stock (in shares)		(854)
Retirement of common stock	0	$ (9)		(54,991)		55,000
Cash dividends declared on common stock	(30,088)			(30,088)
Common stock issued	292		292
Common stock issued (in shares)		5
Balance at Sep. 30, 2019	$ 876,947	$ 446	$ 278,898	$ 649,053	$ (30,013)	$ (21,437)
Balance (in shares) at Sep. 30, 2019		44,327