CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 62,567	$ 35,711	$ 45,268
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustments	(12,902)	(15,060)	(600)
Unrealized holding gains (losses) on short-term investments arising during period	(103)	(35)	38
Defined benefit pension plan:
Net loss arising from period (net of tax effect of $0, $0, and $(119))			(183)
Amortization of net actuarial loss included in net periodic pension cost (net of tax effect of $0, $0, and $28)			43
Final settlement of pension plan liability (net of tax effect of $0, $0, and $1,214)			1,901
Net change in defined benefit pension plan			1,761
Cash flow hedges:
Unrealized gains on change in fair value of interest rate swap contracts (net of tax effect of $0, $110, and $724)		195	1,140
Reclassification adjustment for losses included in net income (net of tax effect of $0, $(55), and $(368))		(97)	(580)
Net change in cash flow hedges		98	560
Other comprehensive income (loss), net of tax	(13,005)	(14,997)	1,759
Total comprehensive income, net of tax	$ 49,562	$ 20,714	$ 47,027