Financial Instruments

12 Months Ended

Dec. 31, 2011

2.	Financial Instruments

Our financial instruments consist primarily of investments in cash and cash equivalents, receivables and certain other assets, and accounts payable, which approximate fair value at December 31, 2011, due to their short term nature. The carrying amounts of our debt obligations approximate fair value based on future payments discounted at current interest rates for similar obligations or interest rates which fluctuate with the market.

Concentrations of credit risk:

Financial instruments that potentially subject us to credit risk consist principally of cash and accounts receivable. We maintain cash and cash equivalents with various major financial institutions. We perform periodic evaluations of the financial institutions in which our cash is invested. Concentrations of credit risk with respect to trade and contract receivables are limited due to the large number of customers and various geographic areas. Additionally, we perform ongoing credit evaluations of our customers' financial condition.