Condensed Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Auction Rate Securities [Member]
Other comprehensive income (loss), net of tax:
Available-for-sale Securities Adjustment, Net of Tax	$ (59)	$ (19)	$ (67)	$ (14)
Available-for-sale Securities [Member]
Other comprehensive income (loss), net of tax:
Available-for-sale Securities Adjustment, Net of Tax	52	4	270	35
Net income	11,198	7,899	21,773	13,862
Foreign currency translation adjustments	(2,039)	105	(1,541)	354
Total other comprehensive income (loss), net of tax	(2,046)	90	(1,338)	375
Comprehensive income	$ 9,152	$ 7,989	$ 20,435	$ 14,237