Condensed Statements of Cash Flows (Unaudited) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013
Cash Flows from Operating Activities:
Net loss	$ (17,269)	$ (7,398)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation	1,320	518
Depreciation and amortization expense	78	75
Amortization of investment premiums	96
Issuance of common stock for services rendered	36	9
Other	(3)	8
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	38	(4)
Accounts payable, accrued expenses, and other liabilities	1,947	(1,214)
Net cash used in operating activities	(13,757)	(8,006)
Cash Flows from Investing Activities:
Purchases of available-for-sale securities	(2,619)
Maturities of available-for-sale securities	2,000
Purchases of property and equipment	(533)	(1)
Net cash used in investing activities	(1,152)	(1)
Cash Flows from Financing Activities:
Proceeds from equity financings	37,202	14,721
Dividends paid	(463)	(509)
Proceeds from exercise of common stock warrants and options and employee stock purchases	6,780	2
Payments on capital lease	(2)	(2)
Net cash provided by financing activities	43,517	14,212
Net increase in cash and cash equivalents	28,608	6,205
Cash and cash equivalents, beginning of period	26,278	10,096
Cash and cash equivalents, end of period	$ 54,886	$ 16,301