Cash Equivalents — Cash equivalents consist of highly liquid investments with original or remaining maturities of 90 days or less at the time of purchase that are readily convertible into cash. As of December 31, 2022 and 2021, the Company held $69.8 million and $124.2 million, respectively, of cash and cash equivalents.

Available-for-Sale Investment — The Thirona convertible note is classified as an available-for-sale security and is included in other assets in the consolidated balance sheet. Available-for-sale investments are subsequently measured at fair value. Unrealized holding gains and losses are excluded from earnings and reported in other comprehensive income until realized. The Company determines fair value of its available-for-sale investments using level 3 inputs. As of December 31, 2022, the Company evaluated the fair value of its investment in Thirona using a Monte Carlo simulation which resulted in a fair value of $7.1 million. In addition, the Company determined that there was a related credit loss of $0.9 million on the investment which was recognized in the consolidated statements of operations for the year ended December 31, 2022.

Held-to-Maturity Investments — Investments consist of highly liquid investments that are intended to facilitate liquidity and capital preservation. As of December 31, 2022, the Company held $101.1 million of short-term investments and $2.0 million of long-term investments. As of December 31, 2021, the Company held $79.9 million of short-term investments and $56.6 million of long-term investments. The amortization or accretion of the Company’s investments is recognized as interest income in the consolidated statements of operations and was approximately $0.7 million and $0.5 million for the years ended December 31, 2022 and 2021, respectively. No allowance for credit losses on held-to-maturity securities was required as of December 31, 2022 or 2021.

The contractual maturities of the Company’s held to maturity investments as of December 31, 2022 and 2021 are summarized below (in thousands):

	December 31, 2022				December 31, 2021
	Amortized Cost Basis		Aggregate Fair Value		Amortized Cost Basis		Aggregate Fair Value
Due in one year or less⁽¹⁾		152,862		156,976	$	103,733	$	103,669
Due after one year through five years		1,961		1,948		56,619		56,433
Total		154,823		158,924	$	160,352	$	160,102

The fair value of the cash equivalents, long-term and short-term investments are disclosed below (in millions):

	December 31, 2022
	Investment Level	Amortized Cost (Carrying Value)			Gross Unrealized Holding Losses			Estimated Fair Value
Commercial bonds and paper	Level 2	$	66.8		$	(0.6	)	$	66.2
Money market funds	Level 1		51.8			—		$	51.8
U.S. Treasuries	Level 2		36.3			(0.6	)	$	35.7
Total cash equivalents and investments		$	154.9		$	(1.2	)	$	153.7
Less cash equivalents			(51.8	)		—			(51.8	)
Total Investments		$	103.1		$	(1.2	)	$	101.9

	December 31, 2021
	Investment Level	Amortized Cost (Carrying Value)			Gross Unrealized Holding Losses		Estimated Fair Value
Commercial bonds and paper	Level 2	$	115.2		$	0.2	$	115.0
Money market funds	Level 1		21.3			—		21.3
U.S. Treasuries	Level 2		23.9			0.1		23.8
Total cash equivalents and investments		$	160.4		$	0.3	$	160.1
Less cash equivalents			(23.8	)		—		(23.8	)
Total Investments		$	136.6		$	0.3	$	136.3

As of December 31, 2022, there was $0.6 million of accrued interest receivable and $5.1 million of amount receivable on matured investment recognized as prepaid expense and other current assets in our consolidated balance sheets. As of December 31, 2021, there was $0.3 million of accrued interest receivable recognized as other assets in our consolidated balance sheets.