Condensed Consolidated Balance Sheets (Parenthetical) (USD $)	Mar. 31, 2013	Dec. 31, 2012
Condensed Consolidated Balance Sheets
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	50,000,000	50,000,000
Common stock, shares issued	39,142,277	39,024,337
Common stock, shares outstanding	30,800,986	30,825,123
Treasury stock, shares	8,341,291	8,199,214