Fair Value of Financial Instruments	9 Months Ended
Sep. 30, 2019
Fair Value of Financial Instruments [Abstract]
Fair Value of Financial Instruments	4. Fair Value of Financial Instruments 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 up to 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 and approximated fair value as of September 30, 2019. We recognize impairment charges when management believes the decline in the fair value of the investment below the carrying value is other-than-temporary. No impairment charges were recognized on our investments for the three and nine months ended September 30, 2019 and 2018. As of September 30, 2018, we transferred the classification of our investments from available-for-sale to held-to-maturity. As of September 30, 2019, the unrealized holding loss and offsetting discount, created as a result of this reclassification, was fully amortized to interest and other income on the condensed consolidated statement of income. 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 sheet. Fair value of mutual funds is measured using Level 1 inputs. The fair value of the investments in the rabbi trust was $12,452 and $10,872 as of September 30, 2019, and December 31, 2018, respectively. We record trading gains and losses in general and administrative expenses on the condensed consolidated statement 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. Other than as disclosed in Note 5. “Corporate Restructuring Costs” and Note 9. “Leases” as of September 30, 2019 and December 31, 2018, we had no material non-financial assets or liabilities that were measured using Level 3 inputs.

Fair Value of Financial Instruments

9 Months Ended

Sep. 30, 2019

Fair Value of Financial Instruments [Abstract]

4. Fair Value of Financial Instruments

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 up to 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 and approximated fair value as of September 30, 2019. We recognize impairment charges when management believes the decline in the fair value of the investment below the carrying value is other-than-temporary. No impairment charges were recognized on our investments for the three and nine months ended September 30, 2019 and 2018.

As of September 30, 2018, we transferred the classification of our investments from available-for-sale to held-to-maturity. As of September 30, 2019, the unrealized holding loss and offsetting discount, created as a result of this reclassification, was fully amortized to interest and other income on the condensed consolidated statement of income.

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 sheet. Fair value of mutual funds is measured using Level 1 inputs. The fair value of the investments in the rabbi trust was $12,452 and $10,872 as of September 30, 2019, and December 31, 2018, respectively. We record trading gains and losses in general and administrative expenses on the condensed consolidated statement 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.

Other than as disclosed in Note 5. “Corporate Restructuring Costs” and Note 9. “Leases” as of September 30, 2019 and December 31, 2018, we had no material non-financial assets or liabilities that were measured using Level 3 inputs.