Fair value (Details 1) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value at beginning of year	$ (109)
Change in fair value recorded in other income (expense)	(1,800)	0
Reclassification to additional paid-in capital upon the merger	1,909
Fair value at end of year		(109)
Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value at beginning of year	(109)	0
Issuances	0	128
Change in fair value recorded in other income (expense)	1,800	(19)
Reclassification to additional paid-in capital upon the merger	(1,909)	0
Fair value at end of year	$ 0	$ (109)