Financial instruments (Policies)

3 Months Ended

Mar. 31, 2013

Fair Value Disclosures [Abstract]

Fair Value of Variable Rate Indebtedness

The fair value of our variable rate indebtedness is deemed to approximate book value and is a Level 2 input as defined by ASC Topic 820-10-35. The fair value of our fixed-rate indebtedness was based on the net present value of our remaining debt payments at an interest rate commensurate with our variable-rate debt which represents Level 3 inputs as defined in ASC Topic 820-10-35. Note that substantially all of the carrying value of our fixed-rate debt at December 31, 2012 and March 31, 2013 relates to a $1.1 million non-interest bearing note. Because it is non-interest bearing, we have calculated an imputed interest rate on the note and carry the note at a value discounted for such interest.