Condensed Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Auction Rate Securities [Member]
Other comprehensive loss, net of tax:
Available-for-sale Securities Adjustment, Net of Tax	$ 88	$ (11)	$ 21	$ (25)
Available-for-sale Securities [Member]
Other comprehensive loss, net of tax:
Available-for-sale Securities Adjustment, Net of Tax	(101)	41	169	76
Net income	14,373	11,201	36,146	25,063
Foreign currency translation adjustments	(52)	(3,132)	(1,593)	(2,778)
Total other comprehensive loss, net of tax	(65)	(3,102)	(1,403)	(2,727)
Comprehensive income	$ 14,308	$ 8,099	$ 34,743	$ 22,336