Condensed Consolidated Statements of Comprehensive Income (Unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Condensed Consolidated Statements of Comprehensive Income [Abstract]
Net income	$ 11,870	$ 9,015	$ 23,676	$ 20,509
Other comprehensive income, net of tax:
Foreign currency translation adjustments	(4,773)	410	(1,482)	6,318
Unrealized holding losses on short-term investments arising during period		1		1
Unrealized pension plan losses and prior service costs			(9)	4
Cash flow hedges:
Unrealized gains (losses) on change in fair value of interest rate swap contracts (net of tax effect of $(33), $263, $61, and $263)	53	(420)	(98)	(420)
Reclassification adjustment for losses included in net income (net of tax effect of $49, $11, $51, and $11)	80	18	82	18
Net change in cash flow hedges	133	(402)	(16)	(402)
Other comprehensive income, net of tax	(4,640)	9	(1,507)	5,921
Total comprehensive income	$ 7,230	$ 9,024	$ 22,169	$ 26,430