Comprehensive Income (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Comprehensive income
Net income	$ 100,216	$ 68,316
Foreign currency translation adjustments	28,180	17,505
Amortization of net prior service costs and net actuarial losses, net of taxes	3,397	3,249
Adjustments of marketable equity securities, net of taxes	(19)	19
Comprehensive income	131,774	89,089
Comprehensive income (Textual) [Abstract]
Tax effect of amortization of net prior service costs and net actuarial losses	(3,020)	(3,089)
Tax effect of adjustments of marketable equity securities	$ 12	$ (12)