Condensed Consolidated Statements of Comprehensive Income - Unaudited (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Net income	$ 12,072	$ 11,870	$ 26,970	$ 23,676
Other comprehensive income, net of tax:
Foreign currency translation adjustments	(901)	(4,773)	(9,689)	(1,482)
Unrealized holding losses on short-term investments arising during period	(55)		(56)
Defined benefit pension plan:
Net loss arising from period (net of tax effect of $0, $0, $(119), and $0)			(183)
Amortization of prior service cost included in net periodic pension cost (net of tax effect of $0, $0, $28, and $0)			43	(9)
Partial settlement of pension plan liability (net of tax effect of $0, $0, $336, and $0)			546
Net change in defined benefit pension plan			406	(9)
Cash flow hedges:
Unrealized gains (losses) on change in fair value of interest rate swap contracts (net of tax effect of $104, $33, $171, and ($61))	342	133	552	(16)
Reclassification adjustment for losses included in other income (expense) (net of tax effect of $(113), $(49), $(179), and $(51))	(178)	(80)	(282)	(82)
Net change in cash flow hedges	164	53	270	(98)
Other comprehensive income, net of tax	(792)	(4,720)	(9,069)	(1,589)
Total comprehensive income	$ 11,280	$ 7,150	$ 17,901	$ 22,087