Changes in Shareholders' Equity (Schedule of Activity in Shareholders' Equity) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2024	Mar. 31, 2024	Jun. 30, 2023	Mar. 31, 2023	Jun. 30, 2024	Jun. 30, 2023
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at start of the period	$ 973,565	$ 967,320	$ 897,515	$ 867,543	$ 967,320	$ 867,543
Net income	24,720	27,369	26,826	27,086	52,089	53,912
Compensation and benefits paid or payable in shares	2,530	810	811	378
Shares issued to Directors'	903		1,086
Cumulative translation adjustments	(17,653)	(12,070)	(2,389)	14,119
Pension and postretirement liability adjustments	246	382	(724)	(916)
Derivative valuation adjustment	(2,840)	(2,124)	389	(2,902)
Balance at end of the period	$ 973,348	$ 973,565	$ 915,719	897,515	$ 973,348	$ 915,719
Dividends declared per Class A share (in dollars per share)	$ 0.26		$ 0.25		$ 0.52	$ 0.50
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	$ (8,123)	$ (8,122)	$ (7,795)	$ (7,792)
Treasury stock, balance at the end of the period (in shares)	9,661,845				9,661,845
Dividends declared per Class A share (in dollars per share)	$ 0.26	$ 0.26	$ 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)	40,898,000	40,856,000	40,842,000	40,785,000	40,856,000	40,785,000
Balance at start of the period	$ 41	$ 41	$ 41	$ 41	$ 41	$ 41
Compensation and benefits paid or payable in shares (in shares)		42,000		58,000
Shares issued to Directors' (in shares)	10,000
Common stock, balance at the end of the period (in shares)	40,908,000	40,898,000	40,842,000	40,842,000	40,908,000	40,842,000
Balance at end of the period	$ 41	$ 41	$ 41	$ 41	$ 41	$ 41
Additional paid-in capital
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at start of the period	449,028	448,218	441,917	441,540	448,218	441,540
Compensation and benefits paid or payable in shares	2,530	810	811	378
Shares issued to Directors'	903		828
Balance at end of the period	452,461	449,028	443,556	441,917	452,461	443,556
Retained  earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at start of the period	1,030,111	1,010,942	950,415	931,318	1,010,942	931,318
Net income	24,624	27,291	26,672	26,889
Balance at end of the period	1,046,612	1,030,111	969,292	950,415	1,046,612	969,292
Retained  earnings | Common Class A
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends declared	(8,123)	(8,122)	(7,795)	(7,792)
Accumulated items of other comprehensive income
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at start of the period	(147,026)	(133,168)	(134,864)	(144,927)	(133,168)	(144,927)
Cumulative translation adjustments	(17,287)	(12,116)	(2,568)	13,881
Pension and postretirement liability adjustments	246	382	(724)	(916)
Derivative valuation adjustment	(2,840)	(2,124)	389	(2,902)
Balance at end of the period	(166,907)	(147,026)	(137,767)	(134,864)	(166,907)	(137,767)
Treasury Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at start of the period	$ (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	9,675,000	9,675,000	9,662,000	9,675,000
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)	$ (364,923)	$ (364,665)	$ (364,665)
Treasury stock, balance at the end of the period (in shares)	9,662,000	9,662,000	9,663,000	9,675,000	9,662,000	9,663,000
Noncontrolling Interest
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at start of the period	$ 6,076	$ 5,952	$ 4,929	$ 4,494	$ 5,952	$ 4,494
Net income	96	78	154	197
Cumulative translation adjustments	(366)	46	179	238
Balance at end of the period	$ 5,806	$ 6,076	$ 5,262	$ 4,929	$ 5,806	$ 5,262