Summary of significant accounting policies (Tables)

12 Months Ended

Dec. 31, 2015

Summary of significant accounting policies

Marketable securities as of December 31, 2015 consist of the following:


			Gross		Gross
	Amortized		Unrealized		Unrealized		Fair
	Cost		Gains		Losses		Value
	(in thousands)
As of December 31, 2015
Money market funds included in cash and cash equivalents	$	29,601	$	—	$	—	$	29,601
Total money market funds included in cash and cash equivalents	$	29,601	$	—	$	—	$	29,601
Marketable securities:
U.S. Treasury notes		158,166		—		185		157,981
U.S. Government agency bonds		35,121		—		66		35,055
Total marketable securities	$	193,287	$	—	$	251	$	193,036
Total money market funds and marketable securities	$	222,888	$	—	$	251	$	222,637

Estimated fair value of marketable securities by contractual maturity

The estimated fair value of the Company’s marketable securities balance at December 31, 2015, by contractual maturity, is as follows:


Due in one year or less	$	163,028
Due after one year through two years		30,008
Total marketable securities	$	193,036

Outstanding potentially dilutive securities excluded in the calculation of diluted net loss per share

The following table sets forth the outstanding potentially dilutive securities that have been excluded in the calculation of diluted net loss per share attributable to common stockholders because to do so would be anti‑dilutive (in common stock equivalent shares):


	As of December 31,
	2015	2014	2013
Redeemable convertible preferred stock	—	5,882,352	—
Unvested restricted common stock	1,818,261	2,578,817	—
Outstanding stock options	2,905,458	—	—
Total	4,723,719	8,461,169	—