Cash, Cash Equivalents and Marketable Securities

9 Months Ended

Sep. 30, 2018

Cash and Cash Equivalents [Abstract]

Cash, Cash Equivalents, and Marketable Securities

Cash, Cash Equivalents and Marketable SecuritiesThe following table summarizes the amortized cost and fair value of the Company's cash, cash equivalents and marketable securities as of September 30, 2018 (in thousands):

	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Estimated Fair Value
(in thousands)
Current assets:
Cash	$	4,747	$	—	$	—	$	4,747
Cash equivalents:
Commercial paper	58,127		—		—		58,127
Corporate debt securities	1,624		—		—		1,624
Money market funds	97,686		—		—		97,686
Certificate of deposits	854		—		—		854
Total cash equivalents	158,291		—		—		158,291
Total cash and cash equivalents	163,038		—		—		163,038
Marketable securities:
Commercial paper	174,769		1		(1)		174,769
Corporate debt securities	47,416		—		(30)		47,386
Certificate of deposits	118,775		—		—		118,775
U.S. Treasuries	35,173		—		(16)		35,157
Total marketable securities	376,133		1		(47)		376,087
Total cash, cash equivalents and marketable securities	$	539,171	$	1	$	(47)	$	539,125

The following table summarizes the cost and fair value of marketable securities based on stated effective maturities as of September 30, 2018 (in thousands):

	Amortized Cost		Fair Value
Due within one year	$	345,678	$	345,644
Due between one and two years	30,455		30,443
Total	$	376,133	$	376,087

The Company did not hold any marketable securities as of December 31, 2017.

There have been no significant realized gains or losses on available-for-sale securities for the periods presented. Available-for-sale debt securities that were in a continuous loss position but were not deemed to be other than temporarily impaired were immaterial at September 30, 2018.

See Note 4 for further information regarding the fair value of the Company's financial instruments.