Summary of significant accounting policies (Tables)

12 Months Ended

Dec. 31, 2016

Summary of significant accounting policies

Schedule of Marketable securities

Cash, cash equivalents, and marketable securities as of December 31, 2016 and 2015 consist of the following:

	Amortized		Unrealized		Unrealized		Fair
	Cost		Gains		Losses		Value
	(in thousands)
As of December 31, 2016
Money market funds included in cash and cash equivalents	$	36,003	$		$		$	36,003
Marketable securities:
U.S. Treasury notes		130,237		2		66		130,173
U.S. Government agency bonds		7,604		—		—		7,604
Total debt securities	$	137,841	$	2	$	66	$	137,777
Equity securities		1,220		140		—		1,360
Total marketable securities	$	139,061	$	142	$	66	$	139,137
Total money market funds and marketable securities	$	175,064	$	142	$	66	$	175,140
As of December 31, 2015
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

	Amortized		Unrealized		Unrealized		Fair
	Cost		Gains		Losses		Value
	(in thousands)
As of December 31, 2016
Money market funds included in cash and cash equivalents	$	36,003	$		$		$	36,003
Marketable securities:
U.S. Treasury notes		130,237		2		66		130,173
U.S. Government agency bonds		7,604		—		—		7,604
Total debt securities	$	137,841	$	2	$	66	$	137,777
Equity securities		1,220		140		—		1,360
Total marketable securities	$	139,061	$	142	$	66	$	139,137
Total money market funds and marketable securities	$	175,064	$	142	$	66	$	175,140
As of December 31, 2015
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

The estimated fair value of the Company’s marketable securities balance at December 31, 2016, by contractual maturity, is as follows:

Due in one year or less $ 137,777

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,
	2016	2015	2014
Redeemable convertible preferred stock	—	—	5,882,352
Unvested restricted common stock	1,167,984	1,818,261	2,578,817
Outstanding stock options	4,226,265	2,905,458	—
Total	5,394,249	4,723,719	8,461,169