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, 2023	Mar. 31, 2023	Jun. 30, 2022	Mar. 31, 2022	Jun. 30, 2023	Jun. 30, 2022	Oct. 31, 2021
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at beginning of the period	$ 897,515	$ 867,543	$ 864,252	$ 877,605	$ 867,543	$ 877,605
Net income	26,826	27,086	39,369	28,075	53,912	67,444
Compensation and benefits paid or payable in shares	811	378	902	745
Options exercised				7
Purchase of Treasury shares			(41,128)	(43,937)
Shares issued to Directors'	1,086		1,085
Cumulative translation adjustments	(2,389)	14,119	(39,752)	(1,674)
Pension and postretirement liability adjustments	(724)	(916)	234	74
Derivative valuation adjustment	389	(2,902)	3,349	10,018
Balance at end of the period	$ 915,719	$ 897,515	$ 821,782	864,252	$ 915,719	$ 821,782
Dividends declared per Class A share (in dollars per share)	$ 0.25		$ 0.21		$ 0.50	$ 0.42
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	$ (7,795)	$ (7,792)	$ (6,529)	$ (6,661)
Treasury stock, balance at the end of the period (in shares)	9,662,562				9,662,562
Dividends declared per Class A share (in dollars per share)		$ 0.25	$ 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	40,785,000	40,781,000	40,760,000	40,785,000	40,760,000
Balance at beginning of the period	$ 41	$ 41	$ 41	$ 41	$ 41	$ 41
Compensation and benefits paid or payable in shares (in shares)		58,000	4,000	21,000
Common stock, balance at the end of the period (in shares)	40,842,000	40,842,000	40,785,000	40,781,000	40,842,000	40,785,000
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 beginning of the period	441,917	441,540	437,748	436,996	441,540	436,996
Compensation and benefits paid or payable in shares	811	378	902	745
Options exercised				7
Shares issued to Directors'	828		800
Balance at end of the period	443,556	441,917	439,450	437,748	443,556	439,450
Retained  earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at beginning of the period	950,415	931,318	884,133	863,057	931,318	863,057
Net income	26,672	26,889	39,201	27,737
Balance at end of the period	969,292	950,415	916,805	884,133	969,292	916,805
Retained  earnings | Common Class A
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends declared	(7,795)	(7,792)	(6,529)	(6,661)
Accumulated items of other comprehensive income
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at beginning of the period	(134,864)	(144,927)	(137,622)	(145,984)	(144,927)	(145,984)
Cumulative translation adjustments	(2,568)	13,881	(39,661)	(1,730)
Pension and postretirement liability adjustments	(724)	(916)	234	74
Derivative valuation adjustment	389	(2,902)	3,349	10,018
Balance at end of the period	(137,767)	(134,864)	(173,700)	(137,622)	(137,767)	(173,700)
Treasury Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at beginning of the period	$ (364,923)	$ (364,923)	$ (324,080)	$ (280,143)	$ (364,923)	$ (280,143)
Treasury stock, balance at the beginning of the period (in shares)	9,675,000	9,675,000	9,180,000	8,665,000	9,675,000	8,665,000
Purchase of Treasury shares (in shares)			508,000	515,000	0	1,022,717
Purchase of Treasury shares			$ (41,128)	$ (43,937)		$ (85,100)
Shares issued to Directors' (in shares)	(12,000)		(13,000)
Shares issued to Directors'	$ 258		$ 285
Balance at end of the period	$ (364,665)	$ (364,923)	$ (364,923)	$ (324,080)	$ (364,665)	$ (364,923)
Treasury stock, balance at the end of the period (in shares)	9,663,000	9,675,000	9,675,000	9,180,000	9,663,000	9,675,000
Noncontrolling Interest
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at beginning of the period	$ 4,929	$ 4,494	$ 4,032	$ 3,638	$ 4,494	$ 3,638
Net income	154	197	168	338
Cumulative translation adjustments	179	238	(91)	56
Balance at end of the period	$ 5,262	$ 4,929	$ 4,109	$ 4,032	$ 5,262	$ 4,109