Summary of Significant Accounting Policies (Tables)

9 Months Ended

Sep. 30, 2018

Accounting Policies [Abstract]

Summary of Potential Common Shares Excluded from Calculation of Diluted Net Loss per Share

The following potential common shares, presented based on amounts outstanding at each period end, were excluded from the calculation of diluted net loss per share attributable to common stockholders for the periods indicated because including them would have had an anti-dilutive effect:

	Three and Nine Months Ended September 30,
	2018		2017
Stock options to purchase common stock		7,444,040		6,133,596
Unvested restricted stock units		289,908		401,900
		7,733,948		6,535,496

Schedule of Reconciliation of Cash, Cash Equivalents and Restricted Cash

A reconciliation of the cash, cash equivalents, and restricted cash reported within the balance sheet that sum to the total of the same amounts shown in the statement of cash flows is as follows:

	September 30,		December31,		September 30,		December31,
	2018		2017		2017		2016
Cash and cash equivalents	$	55,713	$	36,088	$	46,025	$	54,539
Restricted cash		1,513		1,513		1,513		1,400
Total cash, cash equivalents and restricted cash as shown in the    statement of cash flows	$	57,226	$	37,601	$	47,538	$	55,939