Condensed Consolidated Statements of Comprehensive Income (Unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Condensed Consolidated Statements of Comprehensive Income [Abstract]
Net income	$ 9,413	$ 10,479	$ 33,089	$ 30,988
Other comprehensive income, net of tax:
Foreign currency translation adjustments	6,091	(7,563)	4,609	(1,245)
Unrealized holding gains (losses) on short-term investments arising during period	2	(3)	2	(2)
Unrealized pension plan losses and prior service costs			(9)	4
Cash flow hedges:
Unrealized losses on change in fair value of interest rate swap contracts (net of tax effect of $13, $183, $74, and $446)	(20)	(293)	(118)	(713)
Reclassification adjustment for losses included in net income (net of tax effect of $49, $22, $100, and $33)	78	35	160	53
Net change in cash flow hedges	58	(258)	42	(660)
Other comprehensive income, net of tax	6,151	(7,824)	4,644	(1,903)
Total comprehensive income	$ 15,564	$ 2,655	$ 37,733	$ 29,085