Condensed Statements of Cash Flows (Unaudited) (USD $)	6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010
Operating activities
Net loss	$ (17,707,695)	$ (11,031,058)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	131,748	131,743
Stock-based expense	778,595	252,334
Accretion of bond discount	112,472	(3,076)
Non cash interest expense	471,258	68,882
Change in fair value on preferred stock warrants		(32,057)
Change in operating assets and liabilities:
Accounts and accrued interest receivable	(122,263)
Prepaid expenses and other assets	1,057,154	(18,650)
Accounts payable	1,082,582	415,239
Accrued interest, wages, benefits and other liabilities	878,461	(48,660)
Net cash used in operating activities	(13,317,688)	(10,265,303)
Investing activities
Purchases of property and equipment	(41,257)	(137,768)
Purchases of investments	(151,253,212)	(12,295,754)
Proceeds from sale of investments	96,998,670	21,007,856
Net cash provided by (used in) investing activities	(54,295,799)	8,574,334
Financing activities
Proceeds from issuance of subordinated convertible notes, net of issuance costs	3,590,837
Principal payments on borrowings	(1,337,131)	(3,052,305)
Proceeds from initial public offering, net of issuance costs	78,167,843
Proceeds from the exercise of stock options	41,777	42,623
Net cash provided by (used in) financing activities	80,463,326	(3,009,682)
Net increase (decrease) in cash and cash equivalents	12,849,839	(4,700,651)
Cash and cash equivalents at beginning of period	16,872,783	8,699,372
Cash and cash equivalents at end of period	$ 29,722,622	$ 3,998,721