8. Debt Instruments

        In May 2011, we entered into a $30.0 million credit facility with a syndicate of financial institutions. At our option, drawn amounts under the credit facility bore an interest rate of either an adjusted London Interbank Offered Rate, or LIBOR, plus 2.75% - 3.00% or an alternate base rate plus 1.75% - 2.00%, both of which were per annum rates based on outstanding borrowings. Adjusted LIBOR is LIBOR for a particular interest period multiplied by the statutory reserve rate. The alternate base rate is the greatest of the prime rate, the federal funds effective rate plus 0.5% and adjusted LIBOR plus 1%. In addition, the credit facility included a non-usage charge on the available balance of 0.5% - 0.625% per annum based on outstanding borrowings. Under the credit facility, we could request the issuance of up to $5.0 million in letters of credit by the financial institutions. The annual charge for any outstanding letters of credit was 2.75% - 3.00% per annum based on outstanding borrowings.

        In September 2013, we amended this credit facility. The amendment increased the aggregate commitment amount from $30.0 million to $60.0 million and extended the maturity date from May 12, 2015 to September 12, 2018. The amendment further decreased the interest rate on borrowings by 0.75% to either LIBOR plus 2.00% - 2.25% or an alternate base rate plus 1.00% - 1.25%, both of which are per annum rates based on outstanding borrowings. In addition, the amendment decreased the non-usage fee to 0.375% per annum. The amount of available letters of credit under the amended credit facility was increased from $5.0 million to $15.0 million and the annual charge for outstanding letters of credit was reduced by 0.75% to 2.00% - 2.25% per annum based on outstanding borrowings.

        The amount of borrowings available under the credit facility at any time is based on our monthly accounts receivable balance at such time and the amounts borrowed are collateralized by our personal property, including such accounts receivable but excluding intellectual property. The credit facility contains customary events of default, conditions to borrowing and covenants, including restrictions on our ability to dispose of assets, make acquisitions, incur debt, incur liens and make distributions to stockholders. The credit facility also includes a financial covenant requiring the maintenance of minimum liquidity of at least $5.0 million. During the continuance of an event of a default, the lenders may accelerate amounts outstanding, terminate the credit facility and foreclose on all collateral.

        As part of the original credit facility, we had entered into a cash collateral agreement in connection with the issuance of letters of credit that were used to satisfy deposit requirements under facility leases. Under the amended credit facility, the cash collateral agreement was terminated and, as a result, letters of credit no longer require cash collateral. In connection with the termination of the cash collateral agreement, all cash collateral that was considered restricted cash was returned to us in September 2013.

        In July 2013, we borrowed approximately $10.0 million from the credit facility to enhance our working capital position. This amount was paid off in full in August 2013. As of December 31, 2013 we had no borrowings outstanding, $1.1 million in letters of credit outstanding and $58.9 million of available borrowing capacity under the credit facility.

        As of January 31, 2013, we had no borrowings outstanding, $0.8 million in letters of credit outstanding and $29.2 million of available borrowing capacity under the credit facility. As of January 31, 2013, $0.8 million in cash collateral for letters of credit was considered to be restricted cash and was included in other-long term assets.

        Total debt issuance costs associated with the May 2011 credit facility were $1.0 million, which were amortized as interest expense over the four-year term of the May 2011 credit facility agreement. As part of the amendment, the amortization period for the remaining unamortized costs incurred in connection with the May 2011 credit facility was adjusted to reflect the amended term of the credit facility. We further incurred $0.5 million in debt issuance costs in connection with the amendment, which are being amortized over the term of the amended credit facility. For the twelve months ended January 31, 2012 and 2013 and the eleven months ended December 31, 2013 $0.2 million, $0.3 million and $0.2 million of debt issuance costs, respectively, were amortized and included in interest expense.