Consolidated Balance Sheets (Parenthetical) (USD $)	Dec. 31, 2011	Dec. 31, 2010
Stockholders' equity:
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, authorized (in shares)	100,000,000	100,000,000
Common stock, shares issued (in shares)	47,366,997	49,381,678
Common stock, outstanding (in shares)	47,366,997	49,278,578