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Income taxes (Tables) | 3 Months Ended
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Mar. 31, 2012
Income Tax Disclosure [Abstract] |
Significant components of unrecognized tax positions | The components of our unrecognized tax positions are as follows:
| March 31, 2012 | December 31, 2011
Highly certain tax positions | $ | 15,700 |  | $ | 15,100 |
Other unrecognized tax benefits | 800 |  | 800 |
Gross unrecognized tax benefits | $ | 16,500 |  | $ | 15,900 |
Accrued interest and penalties related to unrecognized tax benefits | 100 |  | 100 |

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- Definition Tabular disclosure of unrecognized tax benefits for which a material change is reasonably possible in the next twelve months, typically including the nature of the uncertainty, the event(s) that could cause a material change, and an estimate of the range of the reasonably possible change or a statement that an estimate of the range cannot be made. An unrecognized tax benefit is the difference between a tax position taken in a tax return and the amounts recognized in the financial statements for which it is more likely than not, based on the technical merits of the position, that the tax position will not be sustained upon examination. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name FASB Interpretation (FIN) -Number 48 -Paragraph 21 -Subparagraph d -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 15 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32718-109319 + Details
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