Changes in Shareholders' Equity (Schedule of Activity in Shareholders' Equity) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2024	Sep. 30, 2023
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at start of the period	$ 973,348	$ 973,565	$ 967,320	$ 915,719	$ 897,515	$ 867,543	$ 967,320	$ 867,543
Net income	18,221	24,720	27,369	27,154	26,826	27,086	70,310	81,066
Compensation and benefits paid or payable in shares	195	2,530	810	2,914	811	378
Shares issued to Directors'		903			1,086
Initial equity related to Noncontrolling interest in Arcari				1,632
Dividends paid to noncontrolling interests	(166)
Cumulative translation adjustments	16,778	(17,653)	(12,070)	(15,784)	(2,389)	14,119
Pension and postretirement liability adjustments	(623)	246	382	34	(724)	(916)
Derivative valuation adjustment	(2,950)	(2,840)	(2,124)	(2,237)	389	(2,902)
Balance at end of the period	$ 996,676	973,348	$ 973,565	$ 921,633	915,719	897,515	$ 996,676	$ 921,633
Dividends declared on Class A Common Stock (in dollars per share)	$ 0.26			$ 0.25			$ 0.78	$ 0.75
Common Class A
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Treasury stock, balance at the beginning of the period (in shares)			9,661,845				9,661,845
Dividends declared on Class A Common Stock	$ (8,127)	$ (8,123)	$ (8,122)	$ (7,799)	$ (7,795)	$ (7,792)
Treasury stock, balance at the end of the period (in shares)	9,661,845						9,661,845
Dividends declared on Class A Common Stock (in dollars per share)	$ 0.26	$ 0.26	$ 0.26	$ 0.25	$ 0.25	$ 0.25
Common Stock | Common Class A
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock, balance at the beginning of the period (in shares)	40,908,000	40,898,000	40,856,000	40,842,000	40,842,000	40,785,000	40,856,000	40,785,000
Balance at start of the period	$ 41	$ 41	$ 41	$ 41	$ 41	$ 41	$ 41	$ 41
Compensation and benefits paid or payable in shares (in shares)	9,000		42,000	15,000		58,000
Shares issued to Directors' (in shares)		(10,000)
Common stock, balance at the end of the period (in shares)	40,917,000	40,908,000	40,898,000	40,857,000	40,842,000	40,842,000	40,917,000	40,857,000
Balance at end of the period	$ 41	$ 41	$ 41	$ 41	$ 41	$ 41	$ 41	$ 41
Additional paid-in capital
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at start of the period	452,461	449,028	448,218	443,556	441,917	441,540	448,218	441,540
Compensation and benefits paid or payable in shares	195	2,530	810	2,914	811	378
Shares issued to Directors'		903			828
Balance at end of the period	452,656	452,461	449,028	446,470	443,556	441,917	452,656	446,470
Retained  earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at start of the period	1,046,612	1,030,111	1,010,942	969,292	950,415	931,318	1,010,942	931,318
Net income	18,029	24,624	27,291	27,109	26,672	26,889
Balance at end of the period	1,056,514	1,046,612	1,030,111	988,602	969,292	950,415	1,056,514	988,602
Retained  earnings | Common Class A
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends declared on Class A Common Stock	(8,127)	(8,123)	(8,122)	(7,799)	(7,795)	(7,792)
Accumulated items of other comprehensive income
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at start of the period	(166,907)	(147,026)	(133,168)	(137,767)	(134,864)	(144,927)	(133,168)	(144,927)
Cumulative translation adjustments	16,931	(17,287)	(12,116)	(15,639)	(2,568)	13,881
Pension and postretirement liability adjustments	(623)	246	382	34	(724)	(916)
Derivative valuation adjustment	(2,950)	(2,840)	(2,124)	(2,237)	389	(2,902)
Balance at end of the period	(153,549)	(166,907)	(147,026)	(155,609)	(137,767)	(134,864)	(153,549)	(155,609)
Treasury Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at start of the period	$ (364,665)	$ (364,665)	$ (364,665)	$ (364,665)	$ (364,923)	$ (364,923)	$ (364,665)	$ (364,923)
Treasury stock, balance at the beginning of the period (in shares)	9,662,000	9,662,000	9,662,000	9,663,000	9,675,000	9,675,000	9,662,000	9,675,000
Compensation and benefits paid or payable in shares (in shares)				1,000
Shares issued to Directors' (in shares)					(12,000)
Shares issued to Directors'					$ 258
Balance at end of the period	$ (364,665)	$ (364,665)	$ (364,665)	$ (364,665)	$ (364,665)	$ (364,923)	$ (364,665)	$ (364,665)
Treasury stock, balance at the end of the period (in shares)	9,662,000	9,662,000	9,662,000	9,662,000	9,663,000	9,675,000	9,662,000	9,662,000
Noncontrolling Interest
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at start of the period	$ 5,806	$ 6,076	$ 5,952	$ 5,262	$ 4,929	$ 4,494	$ 5,952	$ 4,494
Net income	192	96	78	45	154	197
Initial equity related to Noncontrolling interest in Arcari				1,632
Dividends paid to noncontrolling interests	(166)
Cumulative translation adjustments	(153)	(366)	46	(145)	179	238
Balance at end of the period	$ 5,679	$ 5,806	$ 6,076	$ 6,794	$ 5,262	$ 4,929	$ 5,679	$ 6,794