Convertible Preferred Stock - Additional Information (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended	0 Months Ended			0 Months Ended
	Mar. 31, 2014	Jun. 07, 2005 Series G Convertible Preferred Stock	Mar. 31, 2014 Series G Convertible Preferred Stock	Dec. 31, 2013 Series G Convertible Preferred Stock	Jun. 01, 2009 Series H Convertible Preferred Stock	Mar. 31, 2014 Series H Convertible Preferred Stock	Dec. 31, 2013 Series H Convertible Preferred Stock
Temporary Equity [Line Items]
Convertible preferred stock issued		5,391,441	0	5,391,441	4,124,986	0	4,124,986
Convertible preferred stock, per share		$ 11.00		$ 0.0001	$ 16.69		$ 0.0001
Aggregate cash purchase price		$ 59.3			$ 68.8
Convertible preferred stock, net of issuance costs		59.1			63.8
Issuance Costs		$ 0.2			$ 5.0
Total aggregate shares of common stock after conversions	38,065,708