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

Our investments are comprised of U.S. Treasury securities, a corporate debt security, non-marketable equity securities, and an equity method investment. We also maintain a deferred compensation plan with related assets held in a rabbi trust. We designate the appropriate classification of our investments at the time of purchase based upon the intended holding period.

Held-to-Maturity Investments

U.S. Treasury Securities

As of March 31, 2022, we held $539,499 of U.S. Treasury securities with maturities of up to 27 months, of which $240,379 mature within one year. As of December 31, 2021, we held $501,288 of U.S. Treasury securities with maturities of up to 24 months, of which $260,945 matured within one year. Our investments in U.S. Treasury securities are held at amortized cost. The fair value of our held-to-maturity U.S. Treasury security investments is measured using Level 1 inputs (quoted prices for identical assets in active markets). As of March 31, 2022 and December 31, 2021, the fair value of our securities were $532,510 and $500,172, respectively. We recognize a reserve for expected credit losses when lifetime credit losses are expected by management. As of March 31, 2022, management has concluded there is no risk of non-payment with respect to our U.S. Treasury security investments.

Corporate Debt Security

On September 30, 2021, we acquired a promissory note issued by a supplier in exchange for $18,000. The promissory note has a principal balance of $18,000 and bears interest at a rate equal to the 3-month U.S. dollar LIBOR plus a fixed interest spread. Accrued interest is paid quarterly in arrears and principal is payable in accordance with an amortization schedule beginning on December 31, 2022. The promissory note matures on September 30, 2028. Our investment in the corporate debt security is held at amortized cost. As of March 31, 2022, we maintained a reserve of $216 for expected credit losses associated with the investment. As of March 31, 2022, we determined the fair value of the investment to be $17,500. The fair value of the Corporate Debt Security is measured using Level 3 (unobservable) inputs. We determined the fair value using an internally-developed valuation model and unobservable inputs include credit and liquidity spreads and effective maturity.

Rabbi Trust

We maintain a rabbi trust to fund obligations under a deferred compensation plan. The rabbi trust is subject to creditor claims in the event of insolvency, but the assets held in the rabbi trust are not available for general corporate purposes. Amounts in the rabbi trust are invested in mutual funds, consistent with the investment choices selected by participants in their Deferred Plan accounts, 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 $20,803 and $19,330 as of March 31, 2022 and December 31, 2021, respectively. We record trading gains and losses, 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 in general and administrative expenses on the condensed consolidated statements of income and comprehensive income.

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, certain long-term investments, operating lease assets, other assets, and goodwill. 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 or if there has been an observable price change of a non-marketable equity security.

The following table summarizes our assets measured at fair value by hierarchy level on a nonrecurring basis:



		Carrying Value
		March 31,
	Level	2022		2021
Leasehold improvements, property and equipment, net	3	$	539	$	1,087
Operating lease assets	3		400		566
Total		$	939	$	1,653

Fair value of these assets was measured using Level 3 inputs (unobservable inputs for the asset or liability). Unobservable inputs include the discount rate, projected restaurant revenues and expenses, and sublease income if we are closing the restaurant. During the three months ended March 31, 2022 and 2021, we recorded asset impairments related to restaurants and offices of $731 and $2,709, respectively. Carrying value after the impairment charges approximates fair value.

On March 23, 2021, we acquired 766 shares of the Series C Preferred Stock of Nuro, Inc. (“Nuro”) in exchange for cash consideration of $10,000. Our investment represents a minority interest and we have determined that we do not have significant influence over Nuro. Nuro is a privately held company, and as such, the preferred shares comprising our investment are illiquid and fair value is not readily determinable. We have elected to measure our investment in the non-marketable equity securities of Nuro at cost, less impairments, if any, plus or minus changes resulting from observable price changes in orderly transactions for the identical or similar investment of the same issuer. The investment is included within long-term investments on the condensed consolidated balance sheets with a carrying value of $15,968 as of March 31, 2022 and December 31, 2021.