Fair Value of Financial Instruments	3 Months Ended
Mar. 31, 2020
Fair Value of Financial Instruments [Abstract]
Fair Value of Financial Instruments	4. Fair Value of Financial Instruments Assets and Liabilities Measured at Fair Value on a Recurring Basis The carrying value of our cash and cash equivalents, accounts receivable and accounts payable approximate fair value because of their short-term nature. Our investments consist of U.S. treasury notes with maturities of less than one year. Fair value of investments is measured using Level 1 inputs (quoted prices for identical assets in active markets). We designate the appropriate classification of our investments at the time of purchase based upon the intended holding period. Investments, all of which are classified as held-to-maturity, are carried at amortized cost. The fair value of these investments exceeded the amortized cost by $2,857 as of March 31, 2020. We recognize a reserve for expected credit losses when lifetime credit losses are expected by management. As of March 31, 2020, our investment portfolio consisted entirely of US Treasury securities for which management has concluded that there is no risk of non-payment. No impairment charges were recognized on our investments for the three months ended March 31, 2020 and 2019. We also maintain a rabbi trust to fund obligations under a deferred compensation plan. Amounts in the rabbi trust are invested in mutual funds, which are designated as trading securities carried at fair value and are included in other assets on the condensed consolidated balance sheets. Fair value of mutual funds is measured using Level 1 inputs. The fair value of the investments in the rabbi trust was $13,279 and $12,811 as of March 31, 2020, and December 31, 2019, respectively. We record trading gains and losses in general and administrative expenses on the condensed consolidated statements of income, along with the offsetting amount related to the increase or decrease in deferred compensation to reflect our exposure to liabilities for payment under the deferred plan. Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis Assets recognized or disclosed at fair value on the condensed consolidated financial statements on a nonrecurring basis include items such as leasehold improvements, property and equipment, operating lease assets, goodwill, and other intangible assets. These assets are measured at fair value if determined to be impaired.

Fair Value of Financial Instruments

3 Months Ended

Mar. 31, 2020

Fair Value of Financial Instruments [Abstract]

4. Fair Value of Financial Instruments

Assets and Liabilities Measured at Fair Value on a Recurring Basis

The carrying value of our cash and cash equivalents, accounts receivable and accounts payable approximate fair value because of their short-term nature.

Our investments consist of U.S. treasury notes with maturities of less than one year. Fair value of investments is measured using Level 1 inputs (quoted prices for identical assets in active markets). We designate the appropriate classification of our investments at the time of purchase based upon the intended holding period.

Investments, all of which are classified as held-to-maturity, are carried at amortized cost. The fair value of these investments exceeded the amortized cost by $2,857 as of March 31, 2020. We recognize a reserve for expected credit losses when lifetime credit losses are expected by management. As of March 31, 2020, our investment portfolio consisted entirely of US Treasury securities for which management has concluded that there is no risk of non-payment. No impairment charges were recognized on our investments for the three months ended March 31, 2020 and 2019.

We also maintain a rabbi trust to fund obligations under a deferred compensation plan. Amounts in the rabbi trust are invested in mutual funds, which are designated as trading securities carried at fair value and are included in other assets on the condensed consolidated balance sheets. Fair value of mutual funds is measured using Level 1 inputs. The fair value of the investments in the rabbi trust was $13,279 and $12,811 as of March 31, 2020, and December 31, 2019, respectively. We record trading gains and losses in general and administrative expenses on the condensed consolidated statements of income, along with the offsetting amount related to the increase or decrease in deferred compensation to reflect our exposure to liabilities for payment under the deferred plan.

Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis

Assets recognized or disclosed at fair value on the condensed consolidated financial statements on a nonrecurring basis include items such as leasehold improvements, property and equipment, operating lease assets, goodwill, and other intangible assets. These assets are measured at fair value if determined to be impaired.