Consolidated Statement of Stockholders' Equity (Deficit) (Parenthetical) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Statement of Stockholders' Equity [Abstract]
Issuance costs of common stock from initial public offering			$ 6,013
Issuance costs of common stock from conversion of convertible notes			18
Issuance costs of common stock from secondary offering		3,564
Issuance costs of common stock from financing agreement, (in usd per share)		$ 3.86
Issuance of common stock from financing agreement, issuance cost		96
Issuance costs of common stock from July 2012 offering	$ 3,328