Fair Value of Financial Instruments	9 Months Ended
Sep. 30, 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 up to 15 months, with $342,819 maturing in less than one year from September 30, 2020. 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 $402 as of September 30, 2020. We recognize a reserve for expected credit losses when lifetime credit losses are expected by management. As of September 30, 2020, our investment portfolio consisted entirely of U.S. 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 and nine months ended September 30, 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 rabbi trust investments in mutual funds is measured using Level 1 inputs. The fair value of the investments in the rabbi trust was $14,774 and $12,811 as of September 30, 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, other assets, goodwill, and other intangible assets. Fair value of these assets are measured using Level 3 inputs (unobservable inputs for the asset or liability). These assets are measured at fair value whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Equity Method Investment On August 6, 2020, we acquired an additional 3.2% of the common stock of a supplier in exchange for cash consideration of $2,500. After this transaction, we own approximately 12.9% of the supplier’s common stock and have invested total cash consideration of $10,000. As we are a significant customer of the supplier and maintain board representation, we are accounting for our investment under the equity method. The investment is included within other assets on the condensed consolidated balance sheet as of September 30, 2020, with a carrying value of $9,816.

Fair Value of Financial Instruments

9 Months Ended

Sep. 30, 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 up to 15 months, with $342,819 maturing in less than one year from September 30, 2020. 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 $402 as of September 30, 2020. We recognize a reserve for expected credit losses when lifetime credit losses are expected by management. As of September 30, 2020, our investment portfolio consisted entirely of U.S. 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 and nine months ended September 30, 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 rabbi trust investments in mutual funds is measured using Level 1 inputs. The fair value of the investments in the rabbi trust was $14,774 and $12,811 as of September 30, 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, other assets, goodwill, and other intangible assets. Fair value of these assets are measured using Level 3 inputs (unobservable inputs for the asset or liability). These assets are measured at fair value whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable.

Equity Method Investment

On August 6, 2020, we acquired an additional 3.2% of the common stock of a supplier in exchange for cash consideration of $2,500. After this transaction, we own approximately 12.9% of the supplier’s common stock and have invested total cash consideration of $10,000. As we are a significant customer of the supplier and maintain board representation, we are accounting for our investment under the equity method. The investment is included within other assets on the condensed consolidated balance sheet as of September 30, 2020, with a carrying value of $9,816.