CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME
Net income	$ 7,807	$ 10,120	$ 26,423	$ 50,015
Other comprehensive income:
Realized losses on short-term investments reclassified from accumulated other comprehensive income, net of tax of $5, $0, $3, and $0, respectively	(10)	(329)	(7)	(329)
Net change in unrealized gains and (losses) on available-for-sale investments, net of tax of ($380), $0, ($2,182) and $0, respectively	832	849	3,350	(803)
Comprehensive income	$ 8,629	$ 10,640	$ 29,766	$ 48,883