Held-to-Maturity Investments — Investments consist of highly liquid investments that are intended to facilitate liquidity and capital preservation. As of March 31, 2022, the Company held $95.2 million of short-term investments and $70.5 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. For the three months ended March 31, 2022, the Company recognized $0.4 million of interest income on investments and $0.3 million of amortization on certain investments. The interest income net of amortization on investments is reflected as interest income, net on the condensed consolidated statement of operations. For the three months ended March 31, 2021, the Company recognized a de minimis amount of interest income on investments. No allowance for credit losses on held-to-maturity securities was required as of March 31, 2022.

Available-for-Sale Investment — The Thirona convertible notes are classified as available-for-sale securities and are included in other assets in the condensed 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. The Company evaluated the fair value of its investment in Thirona as of March 31, 2022 by applying a Monte Carlo simulation and determined that the fair value was $6.9 million. The fair value of the investment in Thirona as of December 31, 2021 was $3.0 million, which approximated carrying value. For the three months ended March 31, 2022, an unrealized holding loss of $1.1 million was recognized as other comprehensive loss in our condensed consolidated statements of comprehensive loss and condensed consolidated statements of stockholders’ deficit.

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

	March 31, 2022
	Investment Level	Amortized Cost (Carrying Value)			Gross Unrealized Holding Losses		Estimated Fair Value
Commercial bonds and paper	Level 2	$	119.5		$	0.8	$	118.8
Money market funds	Level 1		50.7			—		50.7
U.S. Treasuries	Level 2		49.3			0.5		48.8
Total cash equivalents and investments		$	219.5		$	1.3	$	218.3
Less cash equivalents			(53.8	)		—		(53.8	)
Total Investments		$	165.7		$	1.3	$	164.5

	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 March 31, 2022 and December 31, 2021, there was $0.5 million and $0.3 million, respectively, of interest receivable included in our condensed consolidated balance sheets as prepaid expenses and other current assets.