CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Parenthetical) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Statement Of Income And Comprehensive Income [Abstract]
Unrealized gains on marketable securities, income taxes	$ 2,016	$ 258	$ (37)
Unrealized gains (losses) on derivative instruments, income taxes	(751)	(4,392)	(9,969)
Foreign currency translation, income taxes	(2,465)	2,964	3,851
Defined benefit plan adjustment, income taxes	(131)	(1,444)	27
Losses on derivative instruments included in net income, income taxes	4,991	1,313	5,541
Amortization of prior service costs and losses included in net income, income taxes	$ 389	$ 446	$ 553