(12)    Investments

Auction Rate Certificates

Auction rate certificates are long-term securities structured to reset their coupon rates by means of an auction. We accounted for our investment in auction rate certificates as available-for-sale securities. In January 2010, our investment in the auction rate certificates was called by the issuer at par plus accrued interest, or $9,456, resulting in a gain of $425 in the year ended December 31, 2010.

Long Term Restricted Investments

Restricted investments relate to reimbursement obligations under letters of credit issued for the benefit of lessors of office space. As of December 31, 2011 and December 31, 2010, our Long-term restricted investments were $3,973 and $3,396, respectively. During the year ended December 31, 2011, $250 of obligations relating to these letters of credit were terminated and a new letter of credit agreement was entered into for $826 for additional space.