Changes in Stockholders' Equity (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Balance	$ 415,850
Net income	47,041	16,733
Dividends declared	(4,069)
Compensation and benefits paid or payable in Class A Common Stock	(76)
Options exercised	192
Currency translation adjustment	19,327
Amortization of pension liability	1,165
Change in derivative valuation adjustment	(211)
Balance	479,219
Class A Common Stock [Member]
Balance	37
Net income
Dividends declared
Compensation and benefits paid or payable in Class A Common Stock
Options exercised
Currency translation adjustment
Amortization of pension liability
Change in derivative valuation adjustment
Balance	37
Class B Common Stock [Member]
Balance	3
Net income
Dividends declared
Compensation and benefits paid or payable in Class A Common Stock
Options exercised
Currency translation adjustment
Amortization of pension liability
Change in derivative valuation adjustment
Balance	3
Additional Paid-in Capital [Member]
Balance	391,495
Net income
Dividends declared
Compensation and benefits paid or payable in Class A Common Stock	(76)
Options exercised	192
Currency translation adjustment
Amortization of pension liability
Change in derivative valuation adjustment
Balance	391,611
Retained Earnings [Member]
Balance	422,044
Net income	47,041
Dividends declared	(4,069)
Compensation and benefits paid or payable in Class A Common Stock
Options exercised
Currency translation adjustment
Amortization of pension liability
Change in derivative valuation adjustment
Balance	465,016
Accumulated Items of Other Comprehensive Income [Member]
Balance	(139,809)
Net income
Dividends declared
Compensation and benefits paid or payable in Class A Common Stock
Options exercised
Currency translation adjustment	19,327
Amortization of pension liability	1,165
Change in derivative valuation adjustment	(211)
Balance	(119,528)
Treasury Stock [Member]
Balance	(257,920)
Net income
Dividends declared
Compensation and benefits paid or payable in Class A Common Stock
Options exercised
Currency translation adjustment
Amortization of pension liability
Change in derivative valuation adjustment
Balance	$ (257,920)