CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $)	Jun. 30, 2013	Dec. 31, 2012
Stockholders' equity:
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized (in shares)	30,000,000	30,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Class A Stock
Stockholders' equity:
Common Stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common Stock, shares authorized (in shares)	40,000,000	40,000,000
Common Stock, shares issued (in shares)	2,038,920	2,069,187
Common Stock, shares outstanding (in shares)	2,038,920	2,069,187
Common Stock
Stockholders' equity:
Common Stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common Stock, shares authorized (in shares)	160,000,000	160,000,000
Common Stock, shares issued (in shares)	96,662,313	95,223,525
Common Stock, shares outstanding (in shares)	96,662,313	95,223,525