Condensed Statements of Cash Flows (Unaudited) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013
Cash Flows from Operating Activities:
Net loss	$ (26,724)	$ (12,136)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation	2,086	994
Depreciation and amortization expense	135	106
Amortization of investment premiums	149
Issuance of common stock for services rendered	62	18
Other	(8)	41
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(228)	(199)
Accounts payable, accrued expenses, and other liabilities	2,718	(1,499)
Net cash used in operating activities	(21,810)	(12,675)
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	(891)	(4)
Net cash used in investing activities	(1,510)	(4)
Cash Flows from Financing Activities:
Proceeds from equity financings	37,137	40,538
Proceeds from issuance of note payable	850
Dividends paid	(582)	(1,067)
Proceeds from exercise of common stock warrants and options and employee stock purchases	8,132	1,864
Payments on capital lease	(4)	(3)
Net cash provided by financing activities	45,533	41,332
Net increase in cash and cash equivalents	22,213	28,653
Cash and cash equivalents, beginning of period	26,278	10,096
Cash and cash equivalents, end of period	$ 48,491	$ 38,749