Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2018

Accounting Policies [Abstract]

Schedule of assets and liabilities measured at fair value on a recurring basis

The following tables summarize certain information for assets and liabilities measured at fair value on a recurring basis:

	Fair Value Measurements as of
	December 31, 2018
	Estimated Fair Value		Level 1		Level 2		Level 3
Assets
Cash equivalents:
Money market funds	$	94,700	$	94,700	$	—	$	—
Total cash equivalents	94,700		94,700		—		—
Short-term investments:
Commercial paper	$	27,898	$	—	$	27,898	$	—
Corporate bonds	28,012		—		28,012		—
Asset-backed securities	17,055		—		17,055		—
U.S. government securities	17,957		17,957		—		—
Total short-term investments	90,922		17,957		72,965		—
Total assets	$	185,622	$	112,657	$	72,965	$	—

	Fair Value Measurements as of
	December 31, 2017
	Estimated Fair Value		Level 1		Level 2		Level 3
Assets
Cash equivalents:
Money market funds	$	6,446	$	6,446	$	—	$	—
Commercial paper	1,099		—		1,099		—
Total cash equivalents	7,545		6,446		1,099		—
Short-term investments:
Commercial paper	5,384		—		5,384		—
Corporate bonds	1,804		—		1,804		—
Total short-term investments	7,188		—		7,188		—
Total assets	$	14,733	$	6,446	$	8,287	$	—
Liabilities
Preferred stock warrants	$	157	$	—	$	—	$	157

Schedule of reconciliation of preferred stock warrant liabilities

The following table provides a reconciliation of the beginning and ending balances of our preferred stock warrant liabilities:

	Year Ended December 31,
	2018		2017		2016
Balance at beginning of period	$	157	$	53	$	248
Initial fair value of preferred stock warrants issued	103		4		—
Reclassified to equity	(855)		—		—
Change in fair value of preferred stock warrants	595		100		(195)
Balance at end of period	$	—	$	157	$	53