12.	Income Taxes

The components of loss before income taxes are as follows (in thousands):

	Years Ended December 31,
	2015			2014			2013
Domestic	$	(66,411	)	$	(46,998	)	$	(3,107	)
Foreign		(19,126	)		(12,506	)		(11,836	)
Loss before provision for income taxes	$	(85,537	)	$	(59,504	)	$	(14,943	)

The provision for income taxes consists of the following (in thousands):

	Years Ended December 31,
	2015		2014		2013
Current:
Federal	$	—	$	—	$	—
State		2		—		—
Foreign		240		—		—
Total current	$	242	$	—	$	—
Deferred:
Federal	$	—	$	—	$	—
State		—		—		—
Foreign		—		—		—
Total deferred	$	—	$	—	$	—
Total provision from income taxes	$	242	$	—	$	—

The following is the reconciliation between the statutory federal income tax rate and the Company’s effective tax rate:

	Years Ended December 31,
	2015			2014			2013
Tax at statutory federal rate		34.0	%		34.0	%		34.0	%
State tax		—	%		—	%		—	%
Stock-based compensation expense		(4.6	)%		(4.6	)%		(5.7	)%
Net operating losses not benefitted		(21.7	)%		(22.4	)%		(1.6	)%
Foreign net operating losses benefitted		(7.6	)%		(7.1	)%		(26.9	)%
Other		(0.4	)%		0.1	%		0.2	%
Total		(0.3	)%		—	%		—	%

Significant components of the Company’s deferred tax assets are as follows (in thousands):

	December 31,
	2015			2014
Federal and state net operating loss carryforwards	$	53,393		$	44,748
Tax credit carryforwards		26,620			24,395
Foreign net operating loss carryforwards		8,421			6,485
Stock-based compensation		8,512			5,836
Lease obligations		4,335			5,204
Reserves and accruals		4,891			5,075
Deferred revenue		10,484			3,304
Other		915			950
Subtotal		117,571			95,997
Less: Valuation allowance		(116,718	)		(94,731	)
Net deferred tax assets		853			1,266

Fixed assets		(853	)		(1,266	)
Net deferred tax liabilities		(853	)		(1,266	)
Total net deferred tax assets	$	—		$	—

A valuation allowance has been provided to reduce the deferred tax assets to an amount management believes is more likely than not to be realized. Expected realization of the deferred tax assets for which a valuation allowance has not been recognized is based on upon the reversal of existing temporary differences and future taxable income.

The valuation allowance increased by $22.0 million, $21.6 million and $2.2 million for the years ended December 31, 2015, 2014 and 2013, respectively. Due to uncertainty surrounding the realization of the favorable tax attributes in the future tax returns, the Company has established a valuation allowance against its otherwise recognizable net deferred tax assets.

At December 31, 2015, the Company had net operating loss carryforwards available to offset future taxable income of approximately $185.1 million and $270.1 million for federal and state tax purposes, respectively. These carryforwards will begin to expire in 2026 for federal and 2018 for state purposes, if not utilized before these dates. The Company also had foreign net operating loss carryforwards of approximately $35.6 million which expire between 2016 and 2025 if not utilized.

At December 31, 2015, the Company had approximately $27.0 million of federal and $15.6 million of California research and development tax credit and other tax credit carryforwards available to offset future taxable income. The federal credits begin to expire in 2018 and the California research credits have no expiration dates.

The Company tracks a portion of its deferred tax assets attributable to stock option benefits in a separate memorandum account. Therefore, these amounts are not included in the Company’s gross or net deferred tax assets. The benefit of these stock options will not be recorded in equity unless it reduces taxes payable. As of December 31, 2015, the impact related to stock option benefits was approximately $15.8 million.

Federal and state tax laws impose substantial restrictions on the utilization of net operating loss and credit carryforwards in the event of an “ownership change” for tax purposes, as defined in IRC Section 382. The Company reviewed its stock ownership for year ended December 31, 2015 and concluded no ownership changes occurred which would result in a reduction of its net operating loss or in its research and development credits expiring unused. If additional ownership change occurs, the utilization of net operating loss and credit carryforwards could be significantly reduced.

Uncertain Tax Positions

The Company had unrecognized tax benefits of approximately $24.2 million as of December 31, 2015. These unrecognized tax benefits, if recognized, would not affect the effective tax rate. The interest accrued as of December 31, 2015 was immaterial. There were no interest or penalties accrued as of December 31, 2014.

A reconciliation of the beginning and ending amounts of unrecognized income tax benefits during the years ended December 31, 2013, 2014 and 2015 is as follows (in thousands):

	Federal and State
Balance as of January 1, 2013	$	12,545
Increase due to prior positions		294
Increase due to current year position		680
Balance as of December 31, 2013		13,519
Increase due to prior positions		1,493
Increase due to current year position		4,110
Balance as of December 31, 2014		19,122
Decrease due to prior positions		(2,382	)
Increase due to current year position		7,473
Balance as of December 31, 2015	$	24,213

Unrecognized tax benefits may change during the next twelve months for items that arise in the ordinary course of business. The Company does not anticipate a material change to its unrecognized tax benefits over the next twelve months that would affect the Company’s effective tax rate.

The Company classifies interest and penalties as a component of tax expense, if any.

The Company files income tax returns in the U.S. federal jurisdiction, U.S. state and other foreign jurisdictions. The U.S. federal and U.S. state taxing authorities may choose to audit tax returns for tax years beyond the statute of limitation period due to significant tax attribute carryforwards from prior years, making adjustments only to carryforward attributes. The foreign statute of limitation generally remains open from 2006 to 2015. The Company is not currently under audit in any tax jurisdiction.