Changes in Shareholders' Equity (Schedule of Activity in Shareholders' Equity) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020		Mar. 31, 2019
Balance	$ 702,689		$ 608,280
Adoption of accounting standards	(1,443)	[1]	35	[2]
Net income	7,594		29,408
Compensation and benefits paid or payable in shares	(682)		(547)
Options exercised			$ 44
Shares issued to Directors
Dividends declared Class A	$ (5,834)		$ (5,231)
Dividends declared Class B	(307)		(582)
Cumulative translation adjustments	(25,638)		(662)
Pension and postretirement liability adjustments	890		(1,487)
Derivative valuation adjustment	(7,708)		(2,851)
Balance	669,561		626,407
Common Class A [Member]
Balance	$ 39		$ 37
Balance, Shares	39,099,000		37,450,000
Compensation and benefits paid or payable in shares			$ 25
Compensation and benefits paid or payable in shares, Shares	13
Options exercised			3
Balance	$ 39		$ 37
Balance, Shares	39,112,000		37,478,000
Common Class B [Member]
Balance	$ 2		$ 3
Balance, Shares	1,618,000		3,234,000
Balance	$ 2		$ 3
Balance, Shares	1,618,000		3,234,000
Additional paid-in capital [Member]
Balance	$ 432,518		$ 430,555
Compensation and benefits paid or payable in shares	(682)		(547)
Options exercised			44
Balance	431,836		430,052
Retained earnings [Member]
Balance	698,496		589,645
Adoption of accounting standards	(1,443)	[1]	35	[2]
Net income	9,109		29,190
Balance	700,021		613,057
Retained earnings [Member] | Common Class A [Member]
Dividends declared Class A	(5,834)		(5,231)
Retained earnings [Member] | Common Class B [Member]
Dividends declared Class B	(307)		(582)
Total Other Comprehensive Income [Member]
Balance	(175,981)		(158,388)
Cumulative translation adjustments	(25,747)		(654)
Pension and postretirement liability adjustments	890		(1,487)
Derivative valuation adjustment	(7,708)		(2,851)
Balance	(208,546)		(163,380)
Treasury stock [Member]
Balance	$ (256,391)		$ (256,603)
Balance, Shares	8,409		8,419
Balance	$ (256,391)		$ (256,603)
Balance, Shares	8,409		8,419
Noncontrolling Interest [Member]
Balance	$ 4,006		$ 3,031
Net income	(1,515)		218
Cumulative translation adjustments	109		(8)
Balance	$ 2,600		$ 3,241

[1] As described in Note 1, the Company adopted the provisions of ASC 326, Current Expected Credit Losses (CECL) effective January 1, 2020, which resulted in a decrease to Retained earnings of $1.4 million.

[2] The Company adopted ASC 842, Leases effective January 1, 2019, which resulted in an increase to Retained earnings of less than $0.1 million.