Net Income Per Share - (Basic and Diluted Net Income Per Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Earnings Per Share [Abstract]
Net income	$ 8,751	$ 7,789	$ 15,069	$ 13,983
Weighted-average shares outstanding — basic	36,120	35,661	36,072	35,451
Dilutive effect of employee stock plans (in shares)	910	957	915	1,027
Weighted-average shares outstanding — diluted	37,030	36,618	36,987	36,478
Net income per share — basic	$ 0.24	$ 0.22	$ 0.42	$ 0.39
Net income per share — diluted	$ 0.24	$ 0.21	$ 0.41	$ 0.38
Anti-dilutive weighted-average shares related to stock award plans (in shares)	377	353	356	1,347