Consolidated Balance Sheets (Parenthetical) (Unaudited) (USD $)	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012
Statement of Financial Position [Abstract]
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001	$ 0.001
Common stock, authorized (in shares)	100,000,000	100,000,000	100,000,000
Common stock, shares issued (in shares)	46,518,040	46,303,728	47,616,144
Common stock, outstanding (in shares)	46,518,040	46,303,728	47,616,144