CONDENSED CONSOLIDATED BALANCE SHEETS Parenthetical (USD $)	Jun. 30, 2013	Dec. 31, 2012
Stockholders' equity:
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	200,000,000	200,000,000
Common stock, issued (in shares)	40,461,327	40,824,932
Common stock, outstanding (in shares)	40,461,327	40,824,932
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized (in shares)	5,000,000	5,000,000
Preferred stock, issued (in shares)	0	0
Preferred stock, outstanding (in shares)	0	0