Assets and Liabilities Measured at Fair Value on a Recurring Basis

The following table summarizes our assets and liabilities that require fair value measurements on a recurring basis and their respective input levels based on the fair value hierarchy contained in accounting guidance for fair value measurements and disclosures:

Level 2 valuations for our marketable securities which consist of bank certificates of deposit and a U.S. Treasury bill approximate carrying value due to their short-term nature.

Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis

There have been no significant changes to our assets and liabilities measured at fair value on a nonrecurring basis during the six months ended June 30, 2012.

Fair Value of Other Financial Instruments

The carrying amounts of certain of our financial instruments of continuing operations, including cash and cash equivalents, short-term investments, accounts payable and accrued expenses, approximate fair value due to their short-term nature. The carrying amounts and fair values of our long-term obligations of continuing operations are as follows:

At June 30, 2012 and December 31, 2011, we determined the fair value of our long-term obligations using discounted cash flow models with discount rates that represent our respective estimated incremental borrowing rates as of that date for that type of instrument (level 2 inputs).