Unaudited Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Jun. 30, 2015	Dec. 31, 2014
Statement Of Financial Position [Abstract]
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	150,000,000	150,000,000
Common stock, shares issued	80,339,000	79,263,000
Treasury stock, shares	31,997,000	31,310,000