Reconciliations of Equity - Reconciliations of Total Equity (Detail) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Reconciliations of total equity
Beginning Balance		$ 867,472	$ 832,221	$ 892,496	$ 808,185
Issuance of common stock under stock option plan		237	273	392	2,163
Purchase of common stock		(6,510)	(6,104)	(13,753)	(6,181)
Stock-based and deferred compensation		3,043	2,609	4,159	1,249
Net income		35,843	30,210	63,382	55,188
Other comprehensive income		4,345	4,830	(36,044)	9,078
Cash dividends paid:
Common stock		(6,169)	(5,642)	(12,371)	(11,285)
Ending Balance		898,261	858,397	898,261	858,397
Common Stock [Member]
Reconciliations of total equity
Beginning Balance		26,541	26,441	26,493	26,309
Issuance of common stock under stock option plan		4	4	7	43
Stock-based and deferred compensation		7	8	52	101
Cash dividends paid:
Ending Balance		26,552	26,453	26,552	26,453
Additional Paid-in Capital [Member]
Reconciliations of total equity
Beginning Balance		195,661	185,911	193,135	182,881
Issuance of common stock under stock option plan		233	269	385	2,120
Stock-based and deferred compensation		3,053	2,601	5,427	3,780
Cash dividends paid:
Ending Balance		198,947	188,781	198,947	188,781
Treasury Stock [Member]
Reconciliations of total equity
Beginning Balance		(122,685)	(100,098)	(114,139)	(97,389)
Purchase of common stock		(6,510)	(6,104)	(13,753)	(6,181)
Stock-based and deferred compensation		(17)		(1,320)	(2,632)
Cash dividends paid:
Ending Balance		(129,212)	(106,202)	(129,212)	(106,202)
Accumulated Other Comprehensive Income (Loss) [Member]
Reconciliations of total equity
Beginning Balance		(176,546)	(142,580)	(136,170)	(141,483)
Other comprehensive income		4,343	4,857	(36,033)	9,085
Cash dividends paid:
Other	[1]				(5,325)
Ending Balance		(172,203)	(137,723)	(172,203)	(137,723)
Retained Earnings [Member]
Reconciliations of total equity
Beginning Balance		943,807	861,773	922,464	837,107
Net income		35,707	30,218	63,252	55,202
Cash dividends paid:
Common stock		(6,169)	(5,642)	(12,371)	(11,285)
Other	[1]				5,325
Ending Balance		973,345	886,349	973,345	886,349
Noncontrolling Interest [Member]
Reconciliations of total equity
Beginning Balance	[2]	694	774	713	760
Net income	[2]	136	(8)	130	(14)
Other comprehensive income	[2]	2	(27)	(11)	(7)
Cash dividends paid:
Ending Balance	[2]	$ 832	$ 739	$ 832	$ 739

[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.