| Marketable securities | 12 Months Ended | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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| Dec. 31, 2013 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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| Marketable securities | Note 3. Marketable securities 
 There were no available-for-sale securities as of December 31, 2013. 
 Investments in available-for-sale securities at December 31, 2012 were: 
 
 
 The cost and market value of our investments at December 31, 2012 by contractual maturity were: 
 
 
 Investments in certificates of deposit are in brokered certificates of deposit at numerous banking institutions in the USA to take advantage of the FDIC insurance limits. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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- Details 
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- Definition The entire disclosure for investments in certain debt and equity securities. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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