Income taxes (Narrative) (Details) (USD $)
In Millions, unless otherwise specified

12 Months Ended

Dec. 31, 2012

Dec. 31, 2011

Income Taxes Narrative Details

Operating Loss Carryforwards

$ 305.9

Operating loss carryforwards, expiration dates

Will expire in varying amounts from 2017 to 2032

U.S. Federal Research Tax Credit Carryforwards

6.0

U.S. Federal Research Tax Credit Carryforwards, Expiration Dates

Will expire in varying amounts from 2017 to 2032

Annual limit on operating loss carryforwards

In certain circumstances, as specified in the Internal Revenue Code, a 50% or more ownership change by certain combinations of our stockholders during any three-year period would result in limitations on our ability to utilize our net operating loss carry-forwards. We have determined that such a change occurred during 1996 and the annual utilization of loss carry-forwards generated through the period of that change will be limited to approximately $1.6 million.

Accrued penalties and interest

0

0

Unrecognized tax benefits

$ 0

$ 0

Tax years open for examination

The tax years 2009-2011 generally remain open to examination by major taxing jurisdictions in the United States to which we are subject.