Shareholders' Equity (Schedule of Activity in Shareholders' Equity) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Balance	$ 511,290
Balance, shares	32,100,000	32,000,000
Net income	$ 32,585	$ 52,812	$ 57,265
Balance	$ 573,015	$ 511,290
Balance, shares	32,200,000	32,100,000	32,000,000
Common Stock [Member] | Common Class A [Member]
Balance	$ 37	$ 37	$ 37
Balance, shares	37,319,000	37,239,000	37,085,000
Net income
Compensation and benefits paid or payable in shares
Compensation and benefits paid or payable in shares, shares	44,000	53,000	55,000
Options exercised
Options exercised, shares	33,000	26,000	99,000
Shares issued to Directors'
Shares issued to Directors', shares		1,000
Dividends declared
Cumulative translation adjustments
Pension and postretirement liability adjustments
Derivative valuation adjustment
Balance	$ 37	$ 37	$ 37
Balance, shares	37,396,000	37,319,000	37,239,000
Common Stock [Member] | Class B Preferred Stock [Member]
Balance	$ 3	$ 3	$ 3
Balance, shares	3,234,000	3,235,000	3,235,000
Net income
Compensation and benefits paid or payable in shares
Compensation and benefits paid or payable in shares, shares
Options exercised
Options exercised, shares
Shares issued to Directors'
Shares issued to Directors', shares		(1,000)
Dividends declared
Cumulative translation adjustments
Pension and postretirement liability adjustments
Derivative valuation adjustment
Balance	$ 3	$ 3	$ 3
Balance, shares	3,234,000	3,234,000	3,235,000
Additional Paid-in Capital [Member]
Balance	$ 425,953	$ 423,108	$ 418,972
Net income
Compensation and benefits paid or payable in shares	1,564	1,980	1,540
Options exercised	597	667	2,520
Shares issued to Directors'	309	198	76
Dividends declared
Cumulative translation adjustments
Pension and postretirement liability adjustments
Derivative valuation adjustment
Balance	428,423	425,953	423,108
Retained Earnings [Member]
Balance	522,855	491,950	456,105
Net income	33,111	52,733	57,279
Compensation and benefits paid or payable in shares
Options exercised
Shares issued to Directors'
Dividends declared	(21,884)	(21,828)	(21,434)
Cumulative translation adjustments
Pension and postretirement liability adjustments
Derivative valuation adjustment
Balance	534,082	522,855	491,950
Accumulated Other Comprehensive Income (Loss) [Member]
Balance	(184,189)	(158,844)	(107,767)
Net income
Compensation and benefits paid or payable in shares
Options exercised
Shares issued to Directors'
Dividends declared
Cumulative translation adjustments	45,980	(24,643)	(53,415)
Pension and postretirement liability adjustments	1,183	(2,994)	2,941
Derivative valuation adjustment	1,125	2,292	(603)
Balance	(135,901)	(184,189)	(158,844)
Treasury Stock [Member]
Balance	$ (257,136)	$ (257,391)	$ (257,481)
Balance, shares	8,443,000	8,455,000	8,459,000
Net income
Compensation and benefits paid or payable in shares
Options exercised
Shares issued to Directors'	$ 260	$ 255	$ 90
Shares issued to Directors', shares	(12,000)	(12,000)	(4,000)
Dividends declared
Cumulative translation adjustments
Pension and postretirement liability adjustments
Derivative valuation adjustment
Balance	$ (256,876)	$ (257,136)	$ (257,391)
Balance, shares	8,431,000	8,443,000	8,455,000
Noncontrolling Interest [Member]
Balance	$ 3,767	$ 3,690	$ 3,699
Net income	(526)	79	(14)
Compensation and benefits paid or payable in shares
Options exercised
Shares issued to Directors'
Dividends declared
Cumulative translation adjustments	6	(2)	5
Pension and postretirement liability adjustments
Derivative valuation adjustment
Balance	$ 3,247	$ 3,767	$ 3,690