Cash Equivalents and Short-Term Investments (Tables)

12 Months Ended

Dec. 31, 2017

Investments, Debt and Equity Securities [Abstract]

Cash, Cash Equivalents and Investments

The amortized cost and fair value of our cash equivalents and short-term investments are as follows (in thousands):

	December 31, 2017
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Money market funds	$	70,502	$	—	$	—		$	70,502
U.S. Treasury securities	68,702		—		(49		)	68,653
Total	$	139,204	$	—	$	(49	)	$	139,155
Classified as:
Cash equivalents								$	70,502
Short-term investments								68,653
Total								$	139,155

	December 31, 2016
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Money market funds	$	36,412	$	2	$	—		$	36,414
U.S. Treasury securities	62,066		2		(28		)	62,040
Total	$	98,478	$	4	$	(28	)	$	98,454
Classified as:
Cash equivalents								$	36,414
Short-term investments								62,040
Total								$	98,454