Cash Equivalents and Investments (Tables)

3 Months Ended

Mar. 31, 2018

Investments, Debt and Equity Securities [Abstract]

Amortized Cost and Fair Value of Cash Equivalents and Investments

The amortized cost and fair value of cash equivalents and investments at March 31, 2018 and December 31, 2017 were as follows (in thousands):

	March 31, 2018
	Amortized		Gross Unrealized					Fair
	Cost		Gains		Losses			Value
Money market fund	$	17,963	$	—	$	—		$	17,963
U.S. treasury securities		34,986		—		(53	)		34,933
Commercial paper		51,923		—		—			51,923
Corporate debt securities		68,895		—		(250	)		68,645
Total available-for-sale securities	$	173,767	$	—	$	(303	)	$	173,464
Classified as:
Cash equivalents								$	26,938
Short-term investments									116,018
Long-term investments									30,508
Total available-for-sale securities								$	173,464

	December 31, 2017
	Amortized		Gross Unrealized					Fair
	Cost		Gains		Losses			Value
Money market fund	$	29,848	$	—	$	—		$	29,848
U.S. treasury securities		29,005		—		(52	)		28,953
Commercial paper		46,184		—		—			46,184
Corporate debt securities		27,095		—		(67	)		27,028
Total available-for-sale securities	$	132,132	$	—	$	(119	)	$	132,013
Classified as:
Cash equivalents								$	36,813
Short-term investments									87,271
Long-term investments									7,929
Total available-for-sale securities								$	132,013