Reconciliations of Equity - Reconciliations of Total Equity (Detail) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Reconciliations of total equity
Beginning Balance		$ 898,261	$ 858,397	$ 892,496	$ 808,185
Issuance of common stock under stock option plan		2,443	667	2,835	2,830
Purchase of common stock on the open market			(7,003)	(13,753)	(13,184)
Stock-based and deferred compensation		1,899	1,408	6,058	2,657
Net income		33,342	25,880	96,724	81,068
Other comprehensive income		9,467	(18,816)	(26,577)	(9,738)
Cash dividends paid:
Common stock		(6,176)	(5,626)	(18,547)	(16,911)
Ending Balance		939,236	854,907	939,236	854,907
Common Stock [Member]
Reconciliations of total equity
Beginning Balance		26,552	26,453	26,493	26,309
Issuance of common stock under stock option plan		40	13	47	56
Stock-based and deferred compensation		23	15	75	116
Cash dividends paid:
Ending Balance		26,615	26,481	26,615	26,481
Additional Paid-in Capital [Member]
Reconciliations of total equity
Beginning Balance		198,947	188,781	193,135	182,881
Issuance of common stock under stock option plan		2,403	654	2,788	2,774
Stock-based and deferred compensation		2,613	1,969	8,040	5,749
Cash dividends paid:
Ending Balance		203,963	191,404	203,963	191,404
Treasury Stock [Member]
Reconciliations of total equity
Beginning Balance		(129,212)	(106,202)	(114,139)	(97,389)
Purchase of common stock on the open market			(7,003)	(13,753)	(13,184)
Stock-based and deferred compensation		(737)	(576)	(2,057)	(3,208)
Cash dividends paid:
Ending Balance		(129,949)	(113,781)	(129,949)	(113,781)
Accumulated Other Comprehensive Income (Loss) [Member]
Reconciliations of total equity
Beginning Balance		(172,203)	(137,723)	(136,170)	(141,483)
Other comprehensive income		9,430	(18,784)	(26,603)	(9,699)
Cash dividends paid:
Other	[1]				(5,325)
Ending Balance		(162,773)	(156,507)	(162,773)	(156,507)
Retained Earnings [Member]
Reconciliations of total equity
Beginning Balance		973,345	886,349	922,464	837,107
Net income		33,168	25,889	96,420	81,091
Cash dividends paid:
Common stock		(6,176)	(5,626)	(18,547)	(16,911)
Other	[1]				5,325
Ending Balance		1,000,337	906,612	1,000,337	906,612
Noncontrolling Interest [Member]
Reconciliations of total equity
Beginning Balance	[2]	832	739	713	760
Net income	[2]	174	(9)	304	(23)
Other comprehensive income	[2]	37	(32)	26	(39)
Cash dividends paid:
Ending Balance	[2]	$ 1,043	$ 698	$ 1,043	$ 698

[1] Reflects beginning retained earnings adjustment as a result of the Company’s first quarter 2019 adoption of ASU No. 2018-02, Income Statement – Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income.

[2] Reflects the noncontrolling interest in the Company’s China joint venture.