Fair Value Measurements (Tables)

6 Months Ended

Jun. 30, 2018

Fair Value Measurements of Company's Financial Assets

The Company’s financial assets subject to fair value measurements on a recurring basis and the level of inputs used in such measurements were as follows (in thousands) as of June 30, 2018 and December 31, 2017:


	June 30, 2018
Description	Level 1		Level 2		Level 3		Total
Money market fund	$	36,883	$	—	$	—	$	36,883
U.S. treasury securities		—		22,936		—		22,936
Commercial paper		—		61,987		—		61,987
Corporate debt securities		—		67,052		—		67,052

Total assets	$	36,883	$	151,975	$	—	$	188,858


	December 31, 2017
Description	Level 1		Level 2		Level 3		Total
Money market fund	$	29,848	$	—	$	—	$	29,848
U.S. treasury securities		—		28,953		—		28,953
Commercial paper		—		46,184		—		46,184
Corporate debt securities		—		27,028		—		27,028

Total assets	$	29,848	$	102,165	$	—	$	132,013

Summary of Carrying Amount And Estimated Fair Value of Financial Instruments

The carrying amount and estimated fair value of financial instruments not recorded at fair value at June 30, 2018 and December 31, 2017 were as follows (in thousands):


	June 30, 2018				December 31, 2017
	Carrying Amount		Estimated Fair Value		Carrying Amount		Estimated Fair Value
Long-term debt, net ⁽¹⁾	$	14,700	$	14,709	$	4,676	$	4,812

(1)

Carrying amounts of long-term debt were net of unamortized debt discounts of $300,000 and $324,000 as of June 30, 2018 and December 31, 2017, respectively.