Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Allowance for doubtful accounts	$ 226	$ 185
Common stock, par value (per share)	$ 0.001	$ 0.001
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	68,235,179	67,321,769
Common stock, shares outstanding	68,034,386	67,159,511
Treasury stock, shares	200,793	162,258
Convertible Preferred Stock
Convertible preferred stock, par value (per share)	$ 0.001	$ 0.001
Convertible preferred stock, shares authorized	5,000,000	5,000,000
Convertible preferred stock, shares issued	0	0
Convertible preferred stock, shares outstanding	0	0