Net Income Per Share - (Basic and Diluted Net Income Per Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Earnings Per Share [Abstract]
Net income	$ 30,760	$ 30,518	$ 23,979
Weighted-average shares outstanding — basic	35,857	35,650	34,736
Add: Dilutive effect of employee stock plans	861	972	1,041
Weighted-average shares outstanding — diluted	36,718	36,622	35,777
Net income, basic (usd per share)	$ 0.86	$ 0.86	$ 0.69
Net income, diluted (usd per share)	$ 0.84	$ 0.83	$ 0.67
Anti-dilutive weighted-average shares related to stock award plans	555	640	850