Common stock Common stock and preferred stock warrants (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Change in Fair Value Of Warrant Liability Recorded in Other Income (Expense)	$ 0	$ (1,600,000)	$ (1,000,000)
Proceeds from Warrant Exercises	226,000	0	0
Common stock
Class of Warrant or Right, Outstanding	44,491
Class of Warrant or Right, Exercise Price of Warrants or Rights	6.61
Cashless Exercise [Member] | Common stock
Stock Issued During Period, Shares, Exercise of Stock Warrants	0	78,487
Gross Stock Warrants used in cashless exercise		108,155
Cash Exercise [Member]
Proceeds from Warrant Exercises	226,000
Cash Exercise [Member] | Common stock
Stock Issued During Period, Shares, Exercise of Stock Warrants	34,142	0
Proceeds from Warrant Exercises	$ 200,000