Redeemable Convertible Preferred Stock (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance, Preferred Stock Issued and Outstanding				$ 118,343,000
Issuance of preferred stock				76,985,000
Exercise of preferred stock warrants				13,207,000
Accretion of dividends on preferred stock	$ 0	$ 3,628,000	$ 0	9,828,000
Ending Balance, Preferred Stock Issued and Outstanding		218,363,000		218,363,000
Series A [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance, Preferred Stock Issued and Outstanding				2,559,000
Issuance of preferred stock				0
Exercise of preferred stock warrants				0
Accretion of dividends on preferred stock				98,000
Ending Balance, Preferred Stock Issued and Outstanding		2,657,000		2,657,000
Series B [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance, Preferred Stock Issued and Outstanding				22,918,000
Issuance of preferred stock				0
Exercise of preferred stock warrants				5,982,000
Accretion of dividends on preferred stock				960,000
Ending Balance, Preferred Stock Issued and Outstanding		29,860,000		29,860,000
Series C [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance, Preferred Stock Issued and Outstanding				24,749,000
Issuance of preferred stock				0
Exercise of preferred stock warrants				0
Accretion of dividends on preferred stock				1,226,000
Ending Balance, Preferred Stock Issued and Outstanding		25,975,000		25,975,000
Series C-1 [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance, Preferred Stock Issued and Outstanding				5,401,000
Issuance of preferred stock				0
Exercise of preferred stock warrants				7,225,000
Accretion of dividends on preferred stock				306,000
Ending Balance, Preferred Stock Issued and Outstanding		12,932,000		12,932,000
Series D [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance, Preferred Stock Issued and Outstanding				62,716,000
Issuance of preferred stock				0
Exercise of preferred stock warrants				0
Accretion of dividends on preferred stock				3,610,000
Ending Balance, Preferred Stock Issued and Outstanding		66,326,000		66,326,000
Series E [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance, Preferred Stock Issued and Outstanding				0
Issuance of preferred stock				76,985,000
Exercise of preferred stock warrants				0
Accretion of dividends on preferred stock				3,628,000
Ending Balance, Preferred Stock Issued and Outstanding		$ 80,613,000		$ 80,613,000
Redeemable Convertible Preferred Stock [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Ending Balance, Preferred Stock Issued and Outstanding	$ 0		$ 0