Preferred stock (Details) (USD $) In Millions, except Share data, unless otherwise specified	1 Months Ended	0 Months Ended
	Feb. 28, 2014 Director	Feb. 21, 2014	Jan. 21, 2013
Class of Stock [Line Items]
Number of directors appointed	3
Number of directors of the board before expansion	7
Number of directors of the board after expansion	9
Convertible Preferred Stock [Member]
Class of Stock [Line Items]
Issuance of series A preferred stock (in shares)			1,000
Preferred stock conversion to common stock (in shares)		8,200,000
Warrant [Member]
Class of Stock [Line Items]
Adjustments to Additional Paid in Capital, Settlement of Warrant Liability			15.1
Warrant liability mark to market adjustment recorded in other expense, net			2.9
Fair value of warrant liability			15.1