Consolidated Balance Sheets (Parenthetical) (USD $)	Jun. 30, 2013	Dec. 31, 2012
Consolidated Balance Sheets
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized	5,000,000	5,000,000
Series A convertible participating preferred stock, shares issued	0	0
Series A convertible participating preferred stock, shares outstanding	0	0
Common stock, par value (in dollars per share)	$ 0.002	$ 0.002
Common stock, shares authorized	175,000,000	175,000,000
Common stock, shares outstanding	65,457,373	65,113,880
Treasury stock, shares	16,042,202	16,042,202