Shareholders' Equity (Schedule of Activity in Shareholders' Equity) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Balance	$ 513,568
Balance, shares	31,900,000	31,800,000
Net income	$ 57,265	$ 41,749	$ 17,658
Settlement of certain pension plan liabilities	103	5,167
Balance	$ 502,553	$ 513,568
Balance, shares	32,000,000	31,900,000	31,800,000
Common Class B [Member]
Balance, shares	3,235,048
Balance, shares	3,235,048	3,235,048
Common Stock [Member] | Common Class A [Member]
Balance	$ 37	$ 37	$ 37
Balance, shares	37,085,000	36,996,000	36,642,000
Net income
Compensation and benefits paid or payable in shares
Compensation and benefits paid or payable in shares, shares	55,000	47,000	75,000
Conversion of Class B shares to Class A shares
Conversion of Class B shares to Class A shares, shares		1,000
Initial equity related to Noncontrolling interest in ASC
Changes in equity related to Noncontrolling interest in ASC
Options exercised
Options exercised, shares	99,000	41,000	279,000
Shares issued to Directors'
Shares issued to Directors', shares
Dividends declared
Cumulative translation adjustments
Pension and postretirement liability adjustments
Derivative valuation adjustment
Balance	$ 37	$ 37	$ 37
Balance, shares	37,239,000	37,085,000	36,996,000
Common Stock [Member] | Common Class B [Member]
Balance	$ 3	$ 3	$ 3
Balance, shares	3,235,000	3,236,000	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
Conversion of Class B shares to Class A shares, shares		(1,000)
Initial equity related to Noncontrolling interest in ASC
Changes in equity related to Noncontrolling interest in ASC
Options exercised
Options exercised, shares
Shares issued to Directors'
Shares issued to Directors', shares
Dividends declared
Cumulative translation adjustments
Pension and postretirement liability adjustments
Derivative valuation adjustment
Balance	$ 3	$ 3	$ 3
Balance, shares	3,235,000	3,235,000	3,236,000
Additional Paid-in Capital [Member]
Balance	$ 418,972	$ 416,728	$ 395,381
Net income
Compensation and benefits paid or payable in shares	$ 1,540	$ 1,234	$ (902)
Conversion of Class B shares to Class A shares
Initial equity related to Noncontrolling interest in ASC			15,535
Changes in equity related to Noncontrolling interest in ASC		$ (24)
Options exercised	2,520	974	6,670
Shares issued to Directors'	$ 76	$ 60	$ 44
Dividends declared
Cumulative translation adjustments
Pension and postretirement liability adjustments
Derivative valuation adjustment
Balance	$ 423,108	$ 418,972	$ 416,728
Retained Earnings [Member]
Balance	456,105	434,598	435,775
Net income	$ 57,279	$ 41,569	$ 17,517
Compensation and benefits paid or payable in shares
Conversion of Class B shares to Class A shares
Initial equity related to Noncontrolling interest in ASC
Changes in equity related to Noncontrolling interest in ASC
Options exercised
Shares issued to Directors'
Dividends declared	$ (21,434)	$ (20,062)	$ (18,694)
Cumulative translation adjustments
Pension and postretirement liability adjustments
Derivative valuation adjustment
Balance	$ 491,950	$ 456,105	$ 434,598
Accumulated Other Comprehensive Income (Loss) [Member]
Balance	$ (107,767)	$ (49,498)	$ (80,021)
Net income
Compensation and benefits paid or payable in shares
Conversion of Class B shares to Class A shares
Initial equity related to Noncontrolling interest in ASC
Changes in equity related to Noncontrolling interest in ASC
Options exercised
Shares issued to Directors'
Dividends declared
Cumulative translation adjustments	$ (53,415)	$ (55,102)	$ 7,521
Pension and postretirement liability adjustments	2,941	(3,283)	21,101
Derivative valuation adjustment	(603)	116	1,901
Balance	(158,844)	(107,767)	(49,498)
Treasury Stock [Member]
Balance	$ (257,481)	$ (257,571)	$ (257,664)
Balance, shares	8,459,000	8,464,000	8,468,000
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
Initial equity related to Noncontrolling interest in ASC
Changes in equity related to Noncontrolling interest in ASC
Options exercised
Options exercised, shares
Shares issued to Directors'	$ 90	$ 90	$ 93
Shares issued to Directors', shares	(4,000)	(5,000)	(4,000)
Dividends declared
Cumulative translation adjustments
Pension and postretirement liability adjustments
Derivative valuation adjustment
Balance	$ (257,391)	$ (257,481)	$ (257,571)
Balance, shares	8,455,000	8,459,000	8,464,000
Noncontrolling Interest [Member]
Balance	$ 3,699	$ 3,482
Net income	$ (14)	$ 180	$ 141
Compensation and benefits paid or payable in shares
Conversion of Class B shares to Class A shares
Initial equity related to Noncontrolling interest in ASC			$ 3,341
Changes in equity related to Noncontrolling interest in ASC		$ 38
Options exercised
Shares issued to Directors'
Dividends declared
Cumulative translation adjustments	$ 5	$ (1)
Pension and postretirement liability adjustments
Derivative valuation adjustment
Balance	$ 3,690	$ 3,699	$ 3,482