Consolidated Balance Sheets (Unaudited) (Parenthetical) (USD $)	Jun. 30, 2011	Dec. 31, 2010
Stockholders' equity
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	500,000,000	500,000,000
Common stock, shares issued	24,178,734	23,221,287
Treasury stock, shares	1,547,025	1,343,201