Cash, Cash Equivalents, and Investments (Tables)

12 Months Ended

Dec. 31, 2020

Dec. 31, 2019

Cash and Cash Equivalents [Abstract]

Components of Cash, Cash Equivalents and Investments

Cash, cash equivalents, and investments consisted of the following (in thousands):

	December 31,
	2020		2019
Cash	$	266,609	$	155,498
Money market instruments	2,464		15,933
Cash and cash equivalents	269,073		171,431
Treasury bills	35,403		92,914
Corporate bonds	32,714		65,624
Asset-backed securities	25,160		66,680
Sovereign bonds	8,660		6,294
Municipal bonds	1,303		4,630
Certificate of deposit	—		4,328
Current investments	103,240		240,470
Corporate bonds	203,428		146,474
Treasury bills	96,458		216,334
Asset-backed securities	67,058		46,403
Agency bonds	19,006		5,914
Municipal bonds	5,735		2,322
Sovereign bonds	3,440		16,005
Non-current investments	395,125		433,452
	$	767,438	$	845,353

Summary of Available-for-Sale Investments

The following table summarizes the Company’s available-for-sale investments as of December 31, 2020 (in thousands):

	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
Current:
Treasury bills	$	34,978	$	425	$	—	$	35,403
Corporate bonds	32,394		320		—		32,714
Asset-backed securities	24,999		161		—		25,160
Sovereign bonds	8,590		70		—		8,660
Municipal bonds	1,297		6		—		1,303
Non-current:
Corporate bonds	200,549		2,879		—		203,428
Treasury bills	95,522		936		—		96,458
Asset-backed securities	66,329		729		—		67,058
Agency bonds	18,913		93		—		19,006
Municipal bonds	5,725		10				5,735
Sovereign bonds	3,379		61		—		3,440
	$	492,675	$	5,690	$	—	$	498,365

Gross Unrealized Losses and Fair Value for Available-for-Sale Investments

Debt Securities, Available-for-sale, Allowance for Credit Loss

The following table summarizes changes in the allowance for credit losses (in thousands):

Balance as of December 31, 2018	$	—
Balance as of December 31, 2019	—
Increases to the allowance for credit losses	160
Decreases to the allowance for credit losses	(160)
Write-offs	—
Balance as of December 31, 2020	$	—

The following table summarizes changes in the allowance for credit losses (in thousands):

Balance as of December 31, 2018	$	—
Balance as of December 31, 2019	—
Increases to the allowance for credit losses	160
Decreases to the allowance for credit losses	(160)
Write-offs	—
Balance as of December 31, 2020	$	—

Effective Maturity Dates of Available-for-Sale Investments

The following table summarizes the effective maturity dates of the Company’s available-for-sale investments as of December 31, 2020 (in thousands):

	<1 Year		1-2 Years		2-3 Years		3-4 Years		4-5 Years		Total
Corporate bonds	$	32,714	$	69,534	$	119,328	$	13,488	$	1,078	$	236,142
Treasury bills	35,403		68,217		28,241		—		—		131,861
Asset-backed securities	25,160		46,842		18,755		1,461		—		92,218
Agency bonds	—		2,805		16,201		—		—		19,006
Sovereign bonds	8,660		—		3,440		—		—		12,100
Municipal bonds	1,303		5,096		639		—		—		7,038
	$	103,240	$	192,494	$	186,604	$	14,949	$	1,078	$	498,365