Income Taxes (Tables)

12 Months Ended

Dec. 31, 2016

Income Taxes

Schedule of loss before income taxes by jurisdiction

	Year Ended December 31,
	2016		2015		2014
U.S. operations	$	(40,597)	$	(11,823)	$	(8,517)
Foreign operations		(7,482)		(8,740)		—
Loss before income taxes	$	(48,079)	$	(20,563)	$	(8,517)

Reconciliation of statutory to effective rate

	Year Ended December 31,
	2016		2015		2014
Federal statutory income tax rate	(34.0)	%	(34.0)	%	(34.0)	%
State taxes, net of federal benefit	(5.2)		(3.8)		(6.6)
Foreign rate differential	3.2		6.0		—
Permanent differences	1.8		—		—
Research and development tax credits	(2.0)		(1.5)		(1.0)
Change in deferred tax asset valuation allowance	36.2		33.3		41.6
Effective income tax rate	—	%	—	%	—	%

Schedule of Deferred Tax Assets and Liabilities [Table Text Block]

		December 31,
	2016		2015
Deferred tax assets:
Net operating loss carryforwards	$	16,836	$	5,750
Capitalized start up costs		8,840		4,401
Research and development tax credit carryforwards		1,480		500
Capitalized research and development expenses		594		611
Intangible asset		1,403		1,650
Stock‑based compensation expenses		2,629		373
Property and equipment		199		—
Other		2		1
Total deferred tax assets		31,983		13,286
Deferred tax liabilities:
Section 481(a) adjustment		(1,257)		—
Other		—		—
Total deferred tax liabilities		(1,257)		—
Valuation allowance		(30,726)		(13,286)
Net deferred tax assets	$	—	$	—

Changes in deferred tax asset valuation allowance

		Year Ended December 31,
		2016		2015		2014
Valuation allowance at beginning of year	$	(13,286)	$	(6,444)	$	(2,899)
Decreases recorded as benefit to income tax provision		—		—		—
Increases recorded to income tax provision		(17,440)		(6,842)		(3,545)
Valuation allowance as of end of year	$	(30,726)	$	(13,286)	$	(6,444)

Schedule of Changes in Unrecognized Tax Benefits

	Year ended December 31,
	2016		2015		2014
Unrecognized tax benefits at beginning of year	$	(4,400)	$	—	$	—
Increases related to prior year tax provisions				(2,624)		—
Decreases related to prior year tax provisions		4,400		—		—
Increases related to current year tax provisions				(1,776)		—
Unrecognized tax benefits as of end of year	$	—	$	(4,400)	$	—