Shareholders' Equity (Schedule of Activity in Shareholders' Equity) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Balance	$ 502,553
Balance, shares	32,000,000	31,900,000
Net income	$ 52,812	$ 57,265	$ 41,749
Balance	$ 511,290	$ 502,553
Balance, shares	32,100,000	32,000,000	31,900,000
Common Stock [Member] | Common Class A [Member]
Balance	$ 37	$ 37	$ 37
Balance, shares	37,239,000	37,085,000	36,996,000
Net income
Compensation and benefits paid or payable in shares
Compensation and benefits paid or payable in shares, shares	53,000	55,000	47,000
Conversion of Class B shares to Class A shares
Conversion of Class B shares to Class A shares, shares			1,000
Changes in equity related to Noncontrolling interest in ASC
Options exercised
Options exercised, shares	26,000	99,000	41,000
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	37,319,000	37,239,000	37,085,000
Common Stock [Member] | Class B Preferred Stock [Member]
Balance	$ 3	$ 3	$ 3
Balance, shares	3,235,000	3,235,000	3,236,000
Net income
Compensation and benefits paid or payable in shares
Compensation and benefits paid or payable in shares, shares
Conversion of Class B shares to Class A shares, shares			(1,000)
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	3,235,000	3,235,000
Additional Paid-in Capital [Member]
Balance	$ 423,108	$ 418,972	$ 416,728
Net income
Compensation and benefits paid or payable in shares	1,980	1,540	1,234
Conversion of Class B shares to Class A shares
Changes in equity related to Noncontrolling interest in ASC			(24)
Options exercised	667	2,520	974
Shares issued to Directors'	198	76	60
Dividends declared
Cumulative translation adjustments
Pension and postretirement liability adjustments
Derivative valuation adjustment
Balance	425,953	423,108	418,972
Retained Earnings [Member]
Balance	491,950	456,105	434,598
Net income	52,733	57,279	41,569
Compensation and benefits paid or payable in shares
Conversion of Class B shares to Class A shares
Changes in equity related to Noncontrolling interest in ASC
Options exercised
Shares issued to Directors'
Dividends declared	(21,828)	(21,434)	(20,062)
Cumulative translation adjustments
Pension and postretirement liability adjustments
Derivative valuation adjustment
Balance	522,855	491,950	456,105
Accumulated items of other comprehensive income
Balance	(158,844)	(107,767)	(49,498)
Net income
Compensation and benefits paid or payable in shares
Conversion of Class B shares to Class A shares
Changes in equity related to Noncontrolling interest in ASC
Options exercised
Shares issued to Directors'
Dividends declared
Cumulative translation adjustments	(24,643)	(53,415)	(55,102)
Pension and postretirement liability adjustments	(2,994)	2,941	(3,283)
Derivative valuation adjustment	2,292	(603)	116
Balance	(184,189)	(158,844)	(107,767)
Treasury Stock [Member]
Balance	$ (257,391)	$ (257,481)	$ (257,571)
Balance, shares	8,455,000	8,459,000	8,464,000
Net income
Compensation and benefits paid or payable in shares
Compensation and benefits paid or payable in shares, shares
Conversion of Class B shares to Class A shares
Conversion of Class B shares to Class A shares, shares
Changes in equity related to Noncontrolling interest in ASC
Options exercised
Options exercised, shares
Shares issued to Directors'	$ 255	$ 90	$ 90
Shares issued to Directors', shares	(12,000)	(4,000)	(5,000)
Dividends declared
Cumulative translation adjustments
Pension and postretirement liability adjustments
Derivative valuation adjustment
Balance	$ (257,136)	$ (257,391)	$ (257,481)
Balance, shares	8,443,000	8,455,000	8,459,000
Noncontrolling Interest [Member]
Balance	$ 3,690	$ 3,699	$ 3,482
Net income	79	(14)	180
Compensation and benefits paid or payable in shares	0
Conversion of Class B shares to Class A shares
Changes in equity related to Noncontrolling interest in ASC			38
Options exercised	0
Shares issued to Directors'
Dividends declared
Cumulative translation adjustments	(2)	5	(1)
Pension and postretirement liability adjustments
Derivative valuation adjustment
Balance	$ 3,767	$ 3,690	$ 3,699