rates or if the decline in fair value of our publicly traded debt or equity investments is judged to be other-than-temporary. We may suffer losses in principal if we are forced to sell securities that decline in market value due to changes in interest rates. However, because any debt securities we hold are classified as “available-for-sale,” no gains or losses are realized in our statement of income due to changes in interest rates unless such securities are sold prior to maturity or unless declines in market values are determined to be other-than-temporary.  These securities are reported at fair value with the related unrealized gains and losses included in accumulated other comprehensive income, a component of stockholders’ equity, net of tax.



As of January 26, 2014 and January 27, 2013, we had $4.67 billion and $3.73 billion, respectively, in cash, cash equivalents and marketable securities.  Our investment policy requires the purchase of high grade investment securities, the diversification of asset types and includes certain limits on our portfolio duration, as specified in our investment policy guidelines. These guidelines also limit the amount of credit exposure to any one issue, issuer or type of instrument. As of January 26, 2014, we were in compliance with our investment policy.  As of January 26, 2014, our investments in U.S. government agencies and U.S. government sponsored enterprises represented approximately 42% of our total investment portfolio, while the financial sector accounted for approximately 27% of our total investment portfolio. Substantially all of our investments are with A/A3 or better rated securities.



We performed an impairment review of our investment portfolio as of January 26, 2014.  Based on our quarterly impairment review, we concluded that our investments were appropriately valued and did not record any impairment during fiscal year 2014.   



Net realized gains were $2.4 million, $0.5 million and $0.4 million for fiscal years 2014, 2013 and 2012, respectively.  As of January 26, 2014, we had a net unrealized gain of $4.8 million, which was comprised of gross unrealized gains of $7.2 million, offset by $2.4 million of gross unrealized losses.  As of January 27, 2013, we had a net unrealized gain of $10.9 million, which was comprised of gross unrealized gains of $11.7 million, offset by $0.8 million of gross unrealized losses. 



Our accounts receivable are highly concentrated.  One customer accounted for approximately 23% of our accounts receivable balance at January 26, 2014. We maintain an allowance for doubtful accounts for estimated losses resulting from the inability of our customers to make required payments. This allowance consists of an amount identified for specific customers and an amount based on overall estimated exposure. As of January 26, 2014, our allowance for doubtful accounts receivable was 0.2% of our gross accounts receivable balance.



Our cash balances are held in numerous locations throughout the world, including substantial amounts held outside of the United States. As of January 26, 2014, we had cash, cash equivalents and marketable securities of $2.06 billion held within