Changes in Shareholders' Equity (Schedule of Activity in Shareholders' Equity) (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Balance		$ 573,015
Adoption of accounting standards	[1],[2]	(5,412)
Net income		10,482	$ 10,974
Compensation and benefits paid or payable in shares		289
Options exercised		147
Dividends declared		(5,483)
Cumulative translation adjustments		17,639
Pension and postretirement liability adjustments		(13)
Derivative valuation adjustment		4,480
Balance		595,144
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
Additional Paid-in Capital [Member]
Balance		428,423
Adoption of accounting standards	[1],[2]
Net income
Compensation and benefits paid or payable in shares		289
Options exercised		147
Dividends declared
Cumulative translation adjustments
Pension and postretirement liability adjustments
Derivative valuation adjustment
Balance		428,859
Retained Earnings [Member]
Balance		534,082
Adoption of accounting standards	[1],[2]	(5,085)
Net income		10,245
Compensation and benefits paid or payable in shares
Options exercised
Dividends declared		(5,483)
Cumulative translation adjustments
Pension and postretirement liability adjustments
Derivative valuation adjustment
Balance		533,759
Total Other Comprehensive Income [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		17,646
Pension and postretirement liability adjustments		(13)
Derivative valuation adjustment		4,480
Balance		(113,788)
Treasury Stock [Member]
Balance		(256,876)
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		(256,876)
Noncontrolling Interest [Member]
Balance		3,247
Adoption of accounting standards	[1],[2]	(327)
Net income		237
Compensation and benefits paid or payable in shares
Options exercised
Dividends declared
Cumulative translation adjustments		(7)
Pension and postretirement liability adjustments
Derivative valuation adjustment
Balance		$ 3,150

[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 increase to Retained earnings.