Condensed Consolidated Balance Sheets (Parenthetical) (Unaudited) (USD $)	Jun. 30, 2012	Dec. 31, 2011
Statement of Financial Position [Abstract]
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares outstanding	47,413,878	46,878,474
Treasury stock at cost, shares	13,398,367	11,201,634