Cash, Cash Equivalents and Investment Debt Securities

3 Months Ended

Mar. 31, 2020

Cash, Cash Equivalents, and Investment Debt Securities [Abstract]

Cash, Cash Equivalents, and Investment Debt Securities

4.    Cash, Cash Equivalents and Investment Debt Securities

The following table summarizes the Company’s cash, cash equivalents and investment debt securities as of March 31, 2020 and December 31, 2019:

	As of March 31, 2020
			Allowance		Gross		Gross
			for Credit		Unrealized		Unrealized
	Amortized Cost		Losses		Gains		Losses		Fair Value
	(in thousands)
Cash and cash equivalents:
Cash and money market funds	$	41,408	$	—	$	—	$	—	$	41,408
Total cash and cash equivalents		41,408		—		—		—		41,408
Investment debt securities:
Commercial paper		18,478		—		10		—		18,488
Corporate debt securities		486,490		—		189		(1,581)		485,098
U.S. treasuries		4,018		—		24		—		4,042
Total investment debt securities		508,986		—		223		(1,581)		507,628
Total cash, cash equivalents and investment debt securities	$	550,394	$	—	$	223	$	(1,581)	$	549,036

	As of December 31, 2019
			Gross		Gross
			Unrealized		Unrealized
	Amortized Cost		Gains		Losses		Fair Value
	(in thousands)
Cash and cash equivalents:
Cash and money market funds	$	62,557	$	—	$	—	$	62,557
Commercial paper		7,498		—		—		7,498
Total cash and cash equivalents		70,055		—		—		70,055
Investment debt securities:
Commercial paper		42,806		43		(1)		42,848
Corporate debt securities		538,965		835		(81)		539,719
Total investment debt securities		581,771		878		(82)		582,567
Total cash, cash equivalents and investment debt securities	$	651,826	$	878	$	(82)	$	652,622

The aggregate fair value of the Company’s available-for-sale investment debt securities that have been in a continuous unrealized loss position for less than twelve months or twelve months or longer is as follows:

	As of March 31, 2020
	Less than 12 months				12 months or longer				Total
	(in thousands)
			Gross				Gross				Gross
			Unrealized				Unrealized				Unrealized
	Fair Value		Losses		Fair Value		Losses		Fair Value		Losses
Corporate debt securities	$	326,320	$	(1,581)	$	—	$	—	$	326,320	$	(1,581)
Total	$	326,320	$	(1,581)	$	—	$	—	$	326,320	$	(1,581)

	As of December 31, 2019
	Less than 12 months				12 months or longer				Total
	(in thousands)
			Gross				Gross				Gross
			Unrealized				Unrealized				Unrealized
	Fair Value		Losses		Fair Value		Losses		Fair Value		Losses
Commercial paper	$	11,976	$	(1)	$	—	$	—	$	11,976	$	(1)
Corporate debt securities		121,684		(81)		—		—		121,684		(81)
Total	$	133,660	$	(82)	$	—	$	—	$	133,660	$	(82)

At March 31, 2020, the Company had 90 available-for-sale investment debt securities in an unrealized loss position without an allowance for credit losses. Unrealized losses on corporate debt securities have not been recognized into income because the issuers’ bonds are of high credit quality (rated A3/A- or higher), management does not intend to sell and it is likely that management will not be required to sell the securities prior to their anticipated recovery and the decline in fair value is largely due to market conditions and/or changes in interest rates. The issuers continue to make timely interest payments on the bonds. The fair value is expected to recover as the bonds approach maturity.

Accrued interest receivable on available-for-sale investment debt securities totaled $3.3 million at March 31, 2020, is excluded from the estimate of credit losses and is included in Prepaid expenses and other current assets.