Fair Value Measurement (Tables)

12 Months Ended

Dec. 31, 2020

Summary of Investments Measured at Fair Value on Recurring Basis

The following table summarizes the Company’s investments at December 31, 2020 and 2019 measured at fair value on a recurring basis (in thousands):

	December 31, 2020							December 31, 2019
			Gross							Gross
			Unrealized							Unrealized
			Gains			Recorded				Gains			Recorded
	Cost		(Losses)			Basis		Cost		(Losses)			Basis
Current:
Cash equivalents:
Money market funds	$	42,007	$	—		$	42,007	$	35,526	$	—		$	35,526
Total cash equivalents		42,007		—			42,007		35,526		—			35,526
Investments:
Corporate bonds		50,918		884			51,802		53,493		156			53,649
Asset backed securities		36,948		(146	)		36,802		14,017		(13	)		14,004
U.S. government agency securities		7,396		752			8,148		7,408		282			7,690
Mortgage backed securities		4,367		24			4,391		2,737		1			2,738
U.S. treasuries		100		1			101		4,500		9			4,509
Total current investments		99,729		1,515			101,244		82,155		435			82,590
Restricted cash and investments ⁽¹⁾:
Corporate bonds		88,902		4,091			92,993		98,481		1,931			100,412
Mortgage backed securities		48,795		2,356			51,151		62,930		837			63,767
Money market funds		40,063		(4	)		40,059		29,046		—			29,046
U.S. government agency securities		29,737		2,466			32,203		27,885		642			28,527
Mutual funds		5,036		—			5,036		3,466		—			3,466
Supranational bonds		4,775		3			4,778		4,770		30			4,800
U.S. treasuries		4,371		19			4,390		16,906		21			16,927
Asset backed securities		256		4			260		303		—			303
Total restricted cash and investments		221,935		8,935			230,870		243,787		3,461			247,248
Total investments	$	363,671	$	10,450		$	374,121	$	361,468	$	3,896		$	365,364

(1) Included in restricted cash and investments within the consolidated balance sheets as of December 31, 2020 and 2019 is restricted cash of $124.3 million and $197.0 million, respectively, which is excluded from the table above. Restricted cash and investments are classified as current and noncurrent on the balance sheet based on the nature of the restriction.

Summary of Assets Measured at Fair Value on Recurring Basis

The following table summarizes the Company's investments at December 31, 2020 and 2019 measured at fair value on a recurring basis by fair value hierarchy level (in thousands):

	December 31, 2020										December 31, 2019
	Total										Total
	Recorded										Recorded
	Basis		Level 1		Level 2		Level 3		Other ⁽¹⁾		Basis		Level 1		Level 2		Level 3		Other ⁽¹⁾
Cash equivalents:
Money market funds	$	42,007	$	—	$	—	$	—	$	42,007	$	35,526	$	—	$	—	$	—	$	35,526
Investments:
Corporate bonds		51,802		—		51,802		—		—		53,649		—		53,649		—		—
Asset backed securities		36,802		—		36,802		—		—		14,004		—		14,004		—		—
U.S. government agency securities		8,148		—		8,148		—		—		7,690		—		7,690		—		—
Mortgage backed securities		4,391		—		4,391		—		—		2,738		—		2,738		—		—
U.S. treasuries		101		—		101		—		—		4,509		—		4,509		—		—
Restricted cash and investments:
Corporate bonds		92,993		—		92,993		—		—		100,412		—		100,412		—		—
Mortgage backed securities		51,151		—		51,151		—		—		63,767		—		63,767		—		—
Money market funds		40,059		—		—		—		40,059		29,046		—		—		—		29,046
U.S. government agency securities		32,203		—		32,203		—		—		28,527		—		28,527		—		—
Mutual funds		5,036		5,036		—		—		—		3,466		3,466		—		—		—
Supranational bonds		4,778		—		4,778		—		—		4,800		—		4,800		—		—
U.S. treasuries		4,390		—		4,390		—		—		16,927		—		16,927		—		—
Asset backed securities		260		—		260		—		—		303		—		303		—		—
Total investments	$	374,121	$	5,036	$	287,019	$	—	$	82,066	$	365,364	$	3,466	$	297,326	$	—	$	64,572

(1) Investments in money market funds measured at fair value using the net asset value per share practical expedient are not subject to hierarchy level classification disclosure. The Company invests in money market funds that seek to maintain a stable net asset value. These investments include commingled funds that comprise high-quality short-term securities representing liquid debt and monetary instruments where the redemption value is likely to be the fair value. Redemption is permitted daily without written notice.

Summary of Contractual Maturities of Available for Sale Securities

The following table summarizes the contractual maturities of the Company’s available for sale securities at December 31, 2020 and 2019. Actual maturities may differ from contractual maturities because borrowers may have the right to prepay obligations with or without prepayment penalties.

	December 31, 2020
(In thousands)	Less than 1 Year		Between 1 to 5 Years		Between 5 to 10 Years		After 10 Years		Total
Corporate bonds	$	49,308	$	61,315	$	34,172	$	—	$	144,795
Money market funds		82,066		—		—		—		82,066
U.S. government agency securities		1,013		18,668		20,670		—		40,351
Asset backed securities		2		267		—		36,793		37,062
Supranational bonds		4,778		—		—		—		4,778
U.S. treasuries		1,367		1,504		1,620		—		4,491
Total	$	138,534	$	81,754	$	56,462	$	36,793	$	313,543

	December 31, 2019
(In thousands)	Less than 1 Year		Between 1 to 5 Years		Between 5 to 10 Years		After 10 Years		Total
Corporate bonds	$	7,238	$	120,887	$	25,936	$	—	$	154,061
Money market funds		64,572		—		—		—		64,572
U.S. government agency securities		2,128		6,425		27,664		—		36,217
U.S. treasuries		20,632		804		—		—		21,436
Asset backed securities		—		319		—		13,988		14,307
Supranational bonds		—		4,800		—		—		4,800
Total	$	94,570	$	133,235	$	53,600	$	13,988	$	295,393