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, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Sep. 30, 2023	Sep. 30, 2022	Oct. 31, 2021
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at start of the period	$ 915,719	$ 897,515	$ 867,543	$ 821,782	$ 864,252	$ 877,605	$ 867,543	$ 877,605
Net income	27,154	26,826	27,086	10,823	39,369	28,075	81,066	78,267
Compensation and benefits paid or payable in shares	2,914	811	378	835	902	745
Options exercised				10		7
Shares issued to Directors'		1,086			1,085
Purchase of Treasury shares					(41,128)	(43,937)
Initial equity related to Noncontrolling interest in Arcari	1,632
Cumulative translation adjustments	(15,784)	(2,389)	14,119	(38,506)	(39,752)	(1,674)
Pension and postretirement liability adjustments	34	(724)	(916)	(629)	234	74
Settlement of certain pension liabilities				26,198				26,198
Derivative valuation adjustment	(2,237)	389	(2,902)	6,208	3,349	10,018
Balance at end of the period	$ 921,633	915,719	$ 897,515	$ 820,188	821,782	864,252	$ 921,633	$ 820,188
Dividends declared per Class A share (in dollars per share)	$ 0.25			$ 0.21			$ 0.75	$ 0.63
Stock repurchase program, authorized amount									$ 200,000
Common Class A
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Treasury stock, balance at the beginning of the period (in shares)			9,674,542				9,674,542
Dividends declared	$ (7,799)	$ (7,795)	$ (7,792)	$ (6,533)	$ (6,529)	$ (6,661)
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)	$ 0.25	$ 0.25	$ 0.25	$ 0.21	$ 0.21	$ 0.21
Common Stock | Common Class A
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock, balance at the beginning of the period (in shares)	40,842,000	40,842,000	40,785,000	40,785,000	40,781,000	40,760,000	40,785,000	40,760,000
Balance at start of the period	$ 41	$ 41	$ 41	$ 41	$ 41	$ 41	$ 41	$ 41
Compensation and benefits paid or payable in shares (in shares)	15,000		58,000		4,000	21,000
Common stock, balance at the end of the period (in shares)	40,857,000	40,842,000	40,842,000	40,785,000	40,785,000	40,781,000	40,857,000	40,785,000
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	443,556	441,917	441,540	439,450	437,748	436,996	441,540	436,996
Compensation and benefits paid or payable in shares	2,914	811	378	835	902	745
Options exercised				10		7
Shares issued to Directors'		828			800
Balance at end of the period	446,470	443,556	441,917	440,295	439,450	437,748	446,470	440,295
Retained  earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at start of the period	969,292	950,415	931,318	916,805	884,133	863,057	931,318	863,057
Net income	27,109	26,672	26,889	10,694	39,201	27,737
Balance at end of the period	988,602	969,292	950,415	920,966	916,805	884,133	988,602	920,966
Retained  earnings | Common Class A
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends declared	(7,799)	(7,795)	(7,792)	(6,533)	(6,529)	(6,661)
Accumulated items of other comprehensive income
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at start of the period	(137,767)	(134,864)	(144,927)	(173,700)	(137,622)	(145,984)	(144,927)	(145,984)
Cumulative translation adjustments	(15,639)	(2,568)	13,881	(38,450)	(39,661)	(1,730)
Pension and postretirement liability adjustments	34	(724)	(916)	(629)	234	74
Settlement of certain pension liabilities				26,198
Derivative valuation adjustment	(2,237)	389	(2,902)	6,208	3,349	10,018
Balance at end of the period	(155,609)	(137,767)	(134,864)	(180,373)	(173,700)	(137,622)	(155,609)	(180,373)
Treasury Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at start of the period	$ (364,665)	$ (364,923)	$ (364,923)	$ (364,923)	$ (324,080)	$ (280,143)	$ (364,923)	$ (280,143)
Treasury stock, balance at the beginning of the period (in shares)	9,663,000	9,675,000	9,675,000	9,675,000	9,180,000	8,665,000	9,675,000	8,665,000
Compensation and benefits paid or payable in shares	$ 1
Shares issued to Directors' (in shares)		(12,000)			(13,000)
Shares issued to Directors'		$ 258			$ 285
Purchase of Treasury shares (in shares)					508,000	515,000	0	1,022,717
Purchase of Treasury shares					$ (41,128)	$ (43,937)		$ (85,100)
Balance at end of the period	$ (364,665)	$ (364,665)	$ (364,923)	$ (364,923)	$ (364,923)	$ (324,080)	$ (364,665)	$ (364,923)
Treasury stock, balance at the end of the period (in shares)	9,662,000	9,663,000	9,675,000	9,675,000	9,675,000	9,180,000	9,662,000	9,675,000
Noncontrolling Interest
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at start of the period	$ 5,262	$ 4,929	$ 4,494	$ 4,109	$ 4,032	$ 3,638	$ 4,494	$ 3,638
Net income	45	154	197	129	168	338
Initial equity related to Noncontrolling interest in Arcari	1,632
Cumulative translation adjustments	(145)	179	238	(56)	(91)	56
Balance at end of the period	$ 6,794	$ 5,262	$ 4,929	$ 4,182	$ 4,109	$ 4,032	$ 6,794	$ 4,182