Reconciliations of Equity - Reconciliations of Total Equity (Detail) - USD ($) $ in Thousands		3 Months Ended								6 Months Ended
		Jun. 30, 2019		Mar. 31, 2019		Jun. 30, 2018		Mar. 31, 2018		Jun. 30, 2019		Jun. 30, 2018
Reconciliations of total equity
Beginning Balance		$ 832,221		$ 808,185	[1],[2]	$ 801,959		$ 766,218	[2]	$ 808,185	[1],[2]	$ 766,218	[2]
Issuance of common stock under stock option plan		273		1,890		119		3,155
Purchase of common stock		(6,104)		(77)		(9,500)		(2,500)
Stock-based and deferred compensation		2,609		(1,360)		2,443		(1,136)
Net income		30,210	[1],[3]	24,978		33,452	[1],[2],[3]	31,945	[2]	55,188	[1],[3]	65,397	[1],[3]
Other comprehensive income		4,830		4,248		(34,309)		9,567		9,078		(24,742)
Cash dividends paid:
Common stock		(5,642)		(5,643)		(5,068)		(5,092)
Other	[4]							(198)
Ending Balance		858,397	[1]	832,221		789,096		801,959		858,397	[1]	789,096
Common Stock [Member]
Reconciliations of total equity
Beginning Balance		26,441		26,309	[2]	26,268		26,071	[2]	26,309	[2]	26,071	[2]
Issuance of common stock under stock option plan		4		39		3		77
Stock-based and deferred compensation		8		93		8		120
Cash dividends paid:
Ending Balance		26,453		26,441		26,279		26,268		26,453		26,279
Additional Paid-in Capital [Member]
Reconciliations of total equity
Beginning Balance		185,911		182,881	[2]	175,211		170,408	[2]	182,881	[2]	170,408	[2]
Issuance of common stock under stock option plan		269		1,851		116		3,078
Stock-based and deferred compensation		2,601		1,179		2,452		1,725
Cash dividends paid:
Ending Balance		188,781		185,911		177,779		175,211		188,781		177,779
Treasury Stock [Member]
Reconciliations of total equity
Beginning Balance		(100,098)		(97,389)	[2]	(84,042)		(78,561)	[2]	(97,389)	[2]	(78,561)	[2]
Purchase of common stock		(6,104)		(77)		(9,500)		(2,500)
Stock-based and deferred compensation				(2,632)		(17)		(2,981)
Cash dividends paid:
Ending Balance		(106,202)		(100,098)		(93,559)		(84,042)		(106,202)		(93,559)
Accumulated Other Comprehensive Income (Loss) [Member]
Reconciliations of total equity
Beginning Balance		(142,580)		(141,483)	[2]	(90,028)		(99,563)	[2]	(141,483)	[2]	(99,563)	[2]
Other comprehensive income		4,857		4,228		(34,262)		9,535
Cash dividends paid:
Other	[5]			(5,325)
Ending Balance		(137,723)		(142,580)		(124,290)		(90,028)		(137,723)		(124,290)
Retained Earnings [Member]
Reconciliations of total equity
Beginning Balance		861,773		837,107	[2]	773,707		747,045	[2]	837,107	[2]	747,045	[2]
Net income		30,218		24,984		33,454	[2]	31,952	[2]
Cash dividends paid:
Common stock		(5,642)		(5,643)		(5,068)		(5,092)
Other				5,325	[5]			(198)	[4]
Ending Balance		886,349		861,773		802,093		773,707		886,349		802,093
Noncontrolling Interest [Member]
Reconciliations of total equity
Beginning Balance	[6]	774		760	[2]	843		818	[2]	760	[2]	818	[2]
Net income	[6]	(8)		(6)		(2)	[2]	(7)	[2]
Other comprehensive income	[6]	(27)		20		(47)		32
Cash dividends paid:
Ending Balance	[6]	$ 739		$ 774		$ 794		$ 843		$ 739		$ 794

[1] The 2018 amounts for the noted line items have been retrospectively changed from the amounts originally reported as a result of the Company’s first quarter 2019 change in method of accounting for U.S. inventory valuation from LIFO to FIFO.

[2] The retained earnings and net income amounts for the noted line items have been changed from the amounts originally reported as a result of the Company’s first quarter 2019 change in method of accounting for U.S. inventory valuation from LIFO to FIFO.

[3] The 2018 amounts for the noted line items have been retrospectively changed from the amounts originally reported as a result of the Company’s first quarter 2019 change in method of accounting for U.S. inventory valuation from the last in, first out (LIFO) basis to the first in, first out (FIFO) basis.

[4] Reflects beginning retained earnings adjustment as a result of the Company’s first quarter 2018 adoption of ASU No. 2016-16, Income Taxes (Topic 740): Intra-Entity Transfers of Assets Other Than Inventory.

[5] 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.  See Note 19 for more details.

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