Statements of Redeemable Convertible Preferred Stock and Stockholders' Equity (Deficit) (Parentheticals) $ in Thousands	12 Months Ended
	Dec. 31, 2014 USD ($)
Convertible Preferred Stock [Member] | Series D Preferred Stock [Member]
Issuance of Series D redeemable convertible preferred stock, discount associated with investors rights and obligations	$ 6,639
Issuance of Series D redeemable convertible preferred stock, issuance costs	452
Issuance of Series D redeemable convertible preferred stock, issuance costs	$ 452