Changes in Shareholders' Equity (Schedule of Activity in Shareholders' Equity) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019		Mar. 31, 2018
Balance	$ 608,280		$ 57,301
Adoption of accounting standards	35	[1]	(5,395)	[2],[3]
Net income	29,408		7,899
Compensation and benefits paid or payable in shares	(547)		289
Options exercised	44		147
Dividends declared	(5,813)		(5,483)
Cumulative translation adjustments	(662)		17,639
Pension and postretirement liability adjustments	(1,487)		(13)
Derivative valuation adjustment	(2,851)		4,480
Balance	626,407		592,578
Common Stock [Member]
Balance	40		40
Adoption of accounting standards		[1]		[2],[3]
Net income
Compensation and benefits paid or payable in shares
Options exercised
Dividends declared
Cumulative translation adjustments
Pension and postretirement liability adjustments
Derivative valuation adjustment
Balance	40		40
Additional paid in capital [Member]
Balance	430,555		428,423
Adoption of accounting standards		[1]		[2],[3]
Net income
Compensation and benefits paid or payable in shares	(547)		289
Options exercised	44		147
Dividends declared
Cumulative translation adjustments
Pension and postretirement liability adjustments
Derivative valuation adjustment
Balance	430,052		428,859
Retained earnings [Member]
Balance	589,645		534,082
Adoption of accounting standards	35	[1]	(5,068)	[2],[3]
Net income	29,190		7,662
Compensation and benefits paid or payable in shares
Options exercised
Dividends declared
Cumulative translation adjustments
Pension and postretirement liability adjustments
Derivative valuation adjustment
Balance	613,057		531,193
Retained earnings [Member] | Common Class A [Member]
Dividends declared	(5,813)		(5,483)
Retained earnings [Member] | Common Class B [Member]
Dividends declared
Total Other Comprehensive Income [Member]
Balance	(158,388)		(135,901)
Adoption of accounting standards		[1]		[2],[3]
Net income
Compensation and benefits paid or payable in shares
Options exercised
Dividends declared
Cumulative translation adjustments	(654)		17,646
Pension and postretirement liability adjustments	(1,487)		(13)
Derivative valuation adjustment	(2,851)		4,480
Balance	163,380		(113,788)
Treasury stock [Member]
Balance	(256,603)		(256,876)
Adoption of accounting standards		[1]		[2],[3]
Net income
Compensation and benefits paid or payable in shares
Options exercised
Dividends declared
Cumulative translation adjustments
Pension and postretirement liability adjustments
Derivative valuation adjustment
Balance	(256,603)		(256,876)
Noncontrolling Interest [Member]
Balance	3,031		3,247
Adoption of accounting standards		[1]	(327)	[2],[3]
Net income	218		237
Compensation and benefits paid or payable in shares
Options exercised
Dividends declared
Cumulative translation adjustments	(8)		(7)
Pension and postretirement liability adjustments
Derivative valuation adjustment
Balance	$ 3,241		$ 3,150

[1] As described in Note 3, the Company adopted ASC 842, Leases effective January 1, 2019, which resulted in an increase to Retained earnings of less than $0.1 million.

[2] The Company adopted ASC 606 effective January 1, 2018, which resulted in a decrease to Retained earnings of $5.6 million and a $0.3 million decrease to Noncontrolling interest.

[3] The Company adopted ASU 2016-16 effective January 1, 2018, which resulted in a $0.5 million increase to Retained earnings.