Cash, Cash Equivalents, and Investments

12 Months Ended

Dec. 31, 2020

Cash and Cash Equivalents [Abstract]

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

The Company’s cash balance included foreign bank balances totaling $225,853,000 and $123,499,000 as of December 31, 2020 and 2019, respectively.

Treasury bills consist of debt securities issued by the U.S. government; corporate bonds consist of debt securities issued by both domestic and foreign companies; asset-backed securities consist of debt securities collateralized by pools of receivables or loans with credit enhancement; sovereign bonds consist of direct debt issued by foreign governments; municipal bonds consist of debt securities issued by state and local government entities; certificates of deposit are time deposits held by financial institutions with a fixed interest rate; and agency bonds consist of domestic or foreign obligations of government agencies and government-sponsored enterprises that have government backing. All securities are denominated in U.S. Dollars, with the exception of the certificate of deposit held as of December 31, 2019 that was denominated in Korean Won.

Accrued interest receivable is included in "Prepaid expenses and other current assets" on the Consolidated Balance Sheet and amounted to $1,560,000 and $2,874,000 as of December 31, 2020 and 2019, respectively.

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

On January 1, 2020, the Company adopted Accounting Standards Update (ASU) 2016-13, “Measurement of Credit Losses on Financial Instruments,” using the modified-retrospective approach, which requires the Company to apply the standard on a prospective basis with a cumulative-effect adjustment to retained earnings as of the beginning of the period in which the guidance is effective. The Company did not record an adjustment to retained earnings, as there were no debt securities with credit losses as of the adoption date.

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 Company recorded gross realized gains on the sale of debt securities totaling $4,283,000 in 2020, $1,581,000 in 2019, and $669,000 in 2018, and gross realized losses on the sale of debt securities totaling $164,000 in 2020, $129,000 in 2019, and $168,000 in 2018.

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