Income taxes (Credit Carryforwards Narrative) (Details) $ in Millions	12 Months Ended
Dec. 31, 2015 USD ($)
Tax credit carryforwards, expiration dates	The net operating loss carry-forwards and research and development credits available to offset future taxable income, if any, will expire in varying amounts from 2018 to 2035, if not previously utilized.
R&D Tax Credit
Tax Credit Carryforward, Description	At December 31, 2015, we have net operating loss carry-forwards of approximately $359.7 million for federal income tax reporting purposes. In addition, we have research and development tax credits of $6.7 million.
Tax Credit Carryforward, Amount	$ 6.7
Tax Credit Carryforward, Expiration Date	Dec. 31, 2018
Tax credit carryforwards, expiration dates	The net operating loss carry-forwards and research and development credits available to offset future taxable income, if any, will expire in varying amounts from 2018 to 2035, if not previously utilized.
Capital Loss Carryforward
Tax Credit Carryforward, Description	In addition to the tax benefits above, we have $786,000 of capital loss carry-forwards that are scheduled to expire between 2016 and 2017.
Tax Credit Carryforward, Amount	$ 0.8
Tax Credit Carryforward, Expiration Date	Dec. 31, 2017
Tax credit carryforwards, expiration dates	In addition to the tax benefits above, we have $786,000 of capital loss carry-forwards that are scheduled to expire between 2016 and 2017.

The expiration date of each operating loss carryforward included in total operating loss carryforwards, or the applicable range of such expiration dates.

No definition available.

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The amount of the tax credit carryforward, before tax effects, available to reduce future taxable income under enacted tax laws.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32559-109319

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Carryforwards
-URI http://asc.fasb.org/extlink&oid=6506874

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- Definition

A description of the origin, nature, and characteristics of the tax credit carryforward.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32559-109319

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Carryforwards
-URI http://asc.fasb.org/extlink&oid=6506874

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Expiration date of the tax credit carryforward, in CCYY-MM-DD format.

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