Convertible Preferred Stock Warrants - Schedule of Assumptions Used to Determine Fair Value of Convertible Preferred Stock Warrants (Details) (Convertible Preferred Stock [Member], USD $) In Millions, unless otherwise specified	1 Months Ended	0 Months Ended
	Sep. 30, 2013	Dec. 31, 2012 Minimum [Member]	Dec. 31, 2012 Maximum [Member]
Class of Warrant or Right [Line Items]
Remaining contractual term	6 months	2 years 7 months 6 days	8 years 8 months 12 days
Risk-free interest rate		0.30%	1.50%
Volatility		55.00%	64.00%
Change of control probability		25.00%	50.00%
Control premium		40.00%	40.00%
IPO threshold		$ 600	$ 1,800