Concentrations of Credit Risk
Financial instruments that are potentially subject to concentrations of credit risk consist primarily of cash and cash equivalents, marketable securities and trade receivables. Our cash and cash equivalents are generally held with large, diverse financial institutions worldwide to reduce the amount of exposure to any single financial institution. Investment policies have been implemented that limit purchases of marketable debt securities to investment grade securities. We generally do not require collateral to secure accounts receivable. The risk with respect to trade receivables is mitigated by credit evaluations we perform on our customers, the short duration of our payment terms for the significant majority of our customer contracts and by the diversification of our customer base. No single customer accounted for 10% or more of our total revenues in fiscal 2013, 2012 or 2011.