Shareholders' Equity (Schedule of Activity in Shareholders' Equity) (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended												12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Balance				$ 415,850									$ 415,850
Balance, shares				31,300,000				31,200,000					31,300,000	31,200,000
Options exercised, shares													66,700	41,450	7,230
Net income/(loss)	8,200	9,500	(33,700)	47,000	(7,200)	16,700	8,800	16,700	20,500	3,600	7,900	5,600	30,977	34,938	37,636
Dividends declared													(17,246)	(15,942)	(14,923)
Balance	493,511				415,850								493,511	415,850
Balance, shares	31,400,000				31,300,000				31,200,000				31,400,000	31,300,000	31,200,000
Common Class A [Member]
Balance				37				36				36	37	36	36
Balance, shares				36,541,000				36,442,000				36,149,000	36,541,000	36,442,000	36,149,000
Compensation and benefits paid or payable in shares														1
Compensation and benefits paid or payable in shares, shares													34,000	57,000	296,000
Options exercised
Options exercised, shares													67,000	42,000	7,000
Shares issued to Directors
Shares issued to Directors, shares
Net income/(loss)
Dividends declared
Cumulative translation adjustments
Settlement of certain pension plan liabilities
Pension and postretirement liability adjustments
Derivative valuation adjustment
Balance	37				37				36				37	37	36
Balance, shares	36,642,000				36,541,000				36,442,000				36,642,000	36,541,000	36,442,000
Common Class B [Member]
Balance				3				3				3	3	3	3
Balance, shares				3,236,000				3,236,000				3,236,000	3,236,000	3,236,000	3,236,000
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
Net income/(loss)
Dividends declared
Cumulative translation adjustments
Settlement of certain pension plan liabilities
Pension and postretirement liability adjustments
Derivative valuation adjustment
Balance	3				3				3				3	3	3
Balance, shares	3,236,000				3,236,000				3,236,000				3,236,000	3,236,000	3,236,000
Additional Paid-in Capital [Member]
Balance				391,495				387,876				382,674	391,495	387,876	382,674
Compensation and benefits paid or payable in shares													2,573	2,712	4,659
Options exercised													1,352	883	576
Shares issued to Directors													(39)	24	(33)
Net income/(loss)
Dividends declared
Cumulative translation adjustments
Settlement of certain pension plan liabilities
Pension and postretirement liability adjustments
Derivative valuation adjustment
Balance	395,381				391,495				387,876				395,381	391,495	387,876
Retained Earnings [Member]
Balance				422,044				403,048				380,335	422,044	403,048	380,335
Compensation and benefits paid or payable in shares
Options exercised
Shares issued to Directors
Net income/(loss)													30,977	34,938	37,636
Dividends declared													(17,246)	(15,942)	(14,923)
Cumulative translation adjustments
Settlement of certain pension plan liabilities
Pension and postretirement liability adjustments
Derivative valuation adjustment
Balance	435,775				422,044				403,048				435,775	422,044	403,048
Accumulated Other Comprehensive Income (Loss) [Member]
Balance				(139,809)				(106,672)				(82,136)	(139,809)	(106,672)	(82,136)
Compensation and benefits paid or payable in shares
Options exercised
Shares issued to Directors
Net income/(loss)
Dividends declared
Cumulative translation adjustments													11,452	(13,070)	(10,208)
Settlement of certain pension plan liabilities													79,204
Pension and postretirement liability adjustments													(30,584)	(17,749)	(14,052)
Derivative valuation adjustment													(284)	(2,318)	(276)
Balance	(80,021)				(139,809)				(106,672)				(80,021)	(139,809)	(106,672)
Treasury Stock [Member]
Balance				(257,920)				(258,031)				(258,299)	(257,920)	(258,031)	(258,299)
Balance, shares				8,480,000				8,485,000				8,497,000	8,480,000	8,485,000	8,497,000
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													256	111	268
Shares issued to Directors, shares													(12,000)	(5,000)	(12,000)
Net income/(loss)
Dividends declared
Cumulative translation adjustments
Settlement of certain pension plan liabilities
Pension and postretirement liability adjustments
Derivative valuation adjustment
Balance	$ (257,664)				$ (257,920)				$ (258,031)				$ (257,664)	$ (257,920)	$ (258,031)
Balance, shares	8,468,000				8,480,000				8,485,000				8,468,000	8,480,000	8,485,000