Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Net income	$ 51,351	$ 48,879	$ 42,282
Other comprehensive income, net of tax:
Foreign currency translation adjustments	(600)	4,272	(2,866)
Unrealized holding gains (losses) on short-term investments arising during period	38	2	(3)
Defined benefit pension plan:
Net loss arising from period (net of tax effect of $(119), $(62), and $(629))	(183)	(119)	(972)
Amortization of net actuarial loss included in net periodic pension cost (net of tax effect of $28, $97, and $48)	43	152	75
Final settlement of pension plan liability (net of tax effect of $1,214, $0, and $0)	1,901
Net change in defined benefit pension plan	1,761	33	(897)
Cash flow hedges:
Unrealized gains (losses) on change in fair value of interest rate swap contracts (net of tax effect of $724, $128, and $(387))	1,140	200	(684)
Reclassification adjustment for gains (losses) included in net income (net of tax effect of $(368),$(153), and $41)	(580)	(240)	66
Net change in cash flow hedges	560	(40)	(618)
Other comprehensive income (loss), net of tax	1,759	4,267	(4,384)
Total comprehensive income, net of tax	$ 53,110	$ 53,146	$ 37,898