Income Taxes (Tables)

12 Months Ended

Dec. 31, 2018

Income Tax Disclosure [Abstract]

Components of Provision for Income Taxes

The provision for income taxes is based on net loss before income taxes as follows:

	DECEMBER 31,
(in thousands)	2018			2017			2016
Net loss before income taxes:
United States	$	(203,230	)	$	(133,113	)	$	(88,123	)
Other	(29,336		)	(13,750		)	(10,743		)
Net loss before income taxes	$	(232,566	)	$	(146,863	)	$	(98,866	)
The components of the provision for income taxes are as follows:
	DECEMBER 31,
(in thousands, except percentages)	2018			2017			2016
Provision for income taxes:
Current:
United States	$	3		$	(24	)	$	193
Other	—			—			—
Total	$	3		$	(24	)	$	193
Deferred:
United States	$	—		$	(1,734	)	$	—
Other	—			—			—
Total	—			(1,734		)	—
Provision for income taxes	$	3		$	(1,758	)	$	193
Effective tax rate	—		%	1.20		%	(0.19		)%

Summary of Significant Components of Company's Net Deferred Income Tax Assets

Significant components of the Company’s net deferred income tax assets as of December 31, 2018 and 2017 consist of the following:

	DECEMBER 31,
(in thousands)	2018			2017
Net deferred tax assets:
Net operating loss carryforwards	$	112,375		$	58,172
Stock-based compensation	17,734			13,681
U.S. tax credit carryforwards	5,996			4,182
Envisia asset acquisition	5,888			7,107
Other assets	2,857			591
Other liabilities	(1,535		)	(349		)
Valuation allowance	(143,315		)	(83,384		)
Total net deferred income taxes	$	—		$	—

Reconciliation of U.S. Statutory Rate and Effective Tax Rate

A reconciliation of the statutory tax rates and the effective tax rates for the years ended December 31, 2018, 2017 and 2016 is as follows:

	DECEMBER 31,
	2018		2017		2016
U.S. federal tax rate	21.00	%	35.00	%	35.00	%
Impact of federal tax legislation	—	%	25.82	%	—	%
State income taxes, net of federal benefit	4.56	%	7.71	%	5.34	%
Non-taxable foreign loss	0.09	%	(0.51	)%	(2.69	)%
Stock-based compensation	1.97	%	(0.02	)%	(1.46	)%
Other	(1.13	)%	(2.19	)%	(0.18	)%
Change in valuation allowance	(26.49	)%	(64.61	)%	(36.20	)%
Effective tax rate	—	%	1.20	%	(0.19	)%