Changes in Shareholders' Equity (Schedule of Activity in Shareholders' Equity) (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Balance				$ 573,015
Adoption of accounting standards	[1],[2]			(5,413)
Net income		$ 28,484	$ 15,220	69,272	$ 27,427
Compensation and benefits paid or payable in shares				1,879
Options exercised				202
Dividends declared				(16,452)
Cumulative translation adjustments				(23,583)
Pension and postretirement liability adjustments				2,243
Derivative valuation adjustment				7,479
Balance		608,642		608,642
Common Stock [Member]
Balance				40
Adoption of accounting standards	[1],[2]
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				428,423
Adoption of accounting standards	[1],[2]
Net income
Compensation and benefits paid or payable in shares				1,606
Options exercised				202
Dividends declared
Cumulative translation adjustments
Pension and postretirement liability adjustments
Derivative valuation adjustment
Balance		430,231		430,231
Retained earnings [Member]
Balance				534,082
Adoption of accounting standards	[1],[2]			(5,086)
Net income				68,825
Compensation and benefits paid or payable in shares
Dividends declared				(16,452)
Cumulative translation adjustments
Pension and postretirement liability adjustments
Derivative valuation adjustment
Balance		581,369		581,369
Total Other Comprehensive Income [Member] [Member]
Balance				(135,901)
Adoption of accounting standards	[1],[2]
Net income
Compensation and benefits paid or payable in shares
Options exercised
Dividends declared
Cumulative translation adjustments				(23,582)
Pension and postretirement liability adjustments				2,243
Derivative valuation adjustment				7,479
Balance		(149,761)		(149,761)
Treasury stock [Member]
Balance				(256,876)
Adoption of accounting standards	[1],[2]
Net income
Compensation and benefits paid or payable in shares				273
Options exercised
Dividends declared
Cumulative translation adjustments
Pension and postretirement liability adjustments
Derivative valuation adjustment
Balance		(256,603)		(256,603)
Noncontrolling Interest [Member]
Balance				3,247
Adoption of accounting standards	[1],[2]			(327)
Net income				447
Compensation and benefits paid or payable in shares
Options exercised
Dividends declared
Cumulative translation adjustments				(1)
Pension and postretirement liability adjustments
Derivative valuation adjustment
Balance		$ 3,366		$ 3,366

[1] As described in Note 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.

[2] As described in Note 7, the Company adopted ASU 2016-16 effective January 1, 2018, which resulted in a $0.5 million increase to Retained earnings.