Condensed Consolidated Statement of Changes in Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	$0.001 Par Value Common Stock [Member]	Additional Paid-in Capital [Member]	Treasury Stock [Member]	Accumulated Other Comprehensive Loss [Member]	Retained Earnings [Member]	Total
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adoption of new accounting standard (ASC 606), net of tax | ASC 606 [Member]					$ (32,527)	$ (32,527)
Balance at Dec. 31, 2017	$ 50	$ 618,416	$ (39,497)	$ (3,698)	337,074	912,345
Balance (ASC 606 [Member]) at Dec. 31, 2017	$ 50	618,416	$ (39,497)	(3,698)	304,547	$ 879,818
Balance (in shares) at Dec. 31, 2017	50,619,808		(1,214,443)			49,405,365
Balance (in shares) (ASC 606 [Member]) at Dec. 31, 2017	50,619,808		(1,214,443)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Employee equity plans activity	$ 1	21,762				$ 21,763
Employee equity plans activity (in shares)	783,777
Treasury stock			$ (145)			(145)
Treasury stock (in shares)			(2,843)
Net income					66,181	66,181
Foreign currency translations, net of tax				(968)		(968)
Balance at Sep. 30, 2018	$ 51	$ 640,178	$ (39,642)	$ (4,666)	$ 370,728	$ 966,649
Balance (in shares) at Sep. 30, 2018	51,403,585		(1,217,286)			50,186,299