Retirement savings plan (Narrative) (Details) (USD $)	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011
Retirement Savings Plan Narrative Details
401 (k) Employee Maximum Contribution Percentage	6.00%
Company matching employee contribution percentage	50.00%
Contribution to 401 (k) plan	$ 44,000	$ 242,000

The amount of payment into the fund established for purposes of making future disbursements to the individual in accordance with the terms and understanding of the deferred compensation arrangement.

No definition available.

Name:	us-gaap_DeferredCompensationArrangementWithIndividualEmployerContribution
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration