Income Taxes (Tables)

12 Months Ended

Dec. 31, 2016

Income Tax Disclosure [Abstract]

Summary of Deferred Tax Assets

The principal components of the Company’s deferred tax assets are as follows:

	As of December 31,
	2016			2015
Deferred tax assets:
Net operating loss carryforwards	$	102,963		$	67,958
Deferred revenue		2,240			1,732
Accrued bonus		2,963			1,822
Deferred rent		4,137			4,789
Nonaccrual receivables		8,437			9,353
Other		3,509			3,801
Research and development credits		12,512			9,534
Gross deferred tax assets		136,761			98,989
Deferred tax liability		(3,124	)		(6,862	)
Valuation allowance		(133,637	)		(92,127	)
Net deferred tax assets	$	—		$	—

Reconciliation of Income Tax Expense at Federal Tax rate

A reconciliation of the income tax expense at the federal statutory tax rate to the Company’s effective income tax rate follows:

	Year Ended December 31,
	2016			2015			2014
Statutory tax rate		34.0	%		34.0	%		34.0	%
State taxes, net of federal benefit		3.3	%		4.8	%		3.7	%
Permanent differences		(0.9	)%		(1.0	)%		(1.9	)%
Research and development credits		2.6	%		4.5	%		4.9	%
Other		(2.4	)%		(0.6	)%		—
Change in valuation allowance		(36.6	)%		(41.7	)%		(40.7	)%
Effective tax rate		0.0	%		0.0	%		0.0	%