Loss from operations before income taxes is categorized geographically as follows:

	Year Ended December 31,
(in thousands)	2018			2017			2016
United States	$	(152,045	)	$	(40,775	)	$	(64,220	)
Foreign		(2,547	)		718			(7,426	)
Total loss from operations before income taxes	$	(154,592	)	$	(40,057	)	$	(71,646	)

	Year Ended December 31,
(in thousands)	2018			2017			2016
Current income tax expense:
Federal	$	(70	)	$	(12	)	$	(6	)
State		48			23			45
Foreign		677			790			327
Total current income tax expense		655			801			366
Deferred income tax expense:
Federal		(483	)		(16,141	)		4,109
State		562			(248	)		311
Foreign		(586	)		(459	)		(82	)
Total deferred income tax expense		(507	)		(16,848	)		4,338
Total provision for (benefit from) income taxes	$	148		$	(16,047	)	$	4,704

A reconciliation of the Company’s effective tax rate to the federal statutory rate is as follows:

	Year Ended December 31,
(in thousands)	2018			2017			2016
Tax at federal statutory rate	$	(32,464	)	$	(14,020	)	$	(25,076	)
State income tax, net of federal tax benefit		(6,764	)		(3,898	)		(2,255	)
Foreign tax rate differential		626			(493	)		2,805
Stock-based compensation		2,378			2,645			1,981
Transition tax		—			2,261			—
Revaluation of deferred tax assets and liabilities		—			(10,259	)		—
Research and development credits		(5,247	)		(4,028	)		(992	)
Intangible asset write-off		—			—			2,434
Other		(106	)		659			2,092
Change in valuation allowance		41,725			11,086			23,715
Total provision for (benefit from) income taxes	$	148		$	(16,047	)	$	4,704

As of December 31, 2018 and 2017, the tax effects of temporary differences that give rise to significant portions of the Company’s deferred tax assets and liabilities are as follows:

(in thousands)	December 31, 2018			December 31, 2017
Deferred tax assets:
Net operating losses	$	41,419		$	27,046
Tax credits		23,359			12,110
Stock-based compensation		25,208			11,372
Accrued compensation and related expenses		4,061			1,843
Financing obligation- leased facility		29,842			24,122
Other		463			1,462
Total deferred tax assets:		124,352			77,955
Valuation allowance		(81,127	)		(34,664	)
Total deferred tax assets, net of valuation allowance:		43,225			43,291
Deferred tax liabilities:
Depreciation and amortization		(26,844	)		(30,708	)
Goodwill		(19,307	)		(16,017	)
Total deferred tax liabilities:		(46,151	)		(46,725	)
Total net deferred tax liabilities:	$	(2,926	)	$	(3,434	)

As of December 31, 2018, the Company had federal and state net operating losses of $162.2 million and $63.8 million, respectively. If not utilized, the federal and state net operating loss carryforwards will begin to expire in 2019.

As of December 31, 2018, the Company had federal research and development credits of $14.7 million which will begin to expire in 2032; state research and development credits of $10.8 million which will carryforward indefinitely; and foreign research and development credits of $1.1 million which will begin to expire in 2037.

Assessing the realizability of the Company’s deferred tax assets is dependent upon several factors, including the likelihood and amount, if any, of future taxable income in relevant jurisdictions during the periods in which those temporary differences become deductible. The Company has evaluated the criteria for realization of deferred tax assets and, as a result, has determined that certain deferred tax assets are not realizable on a more likely than not basis. Accordingly, the Company recorded a valuation allowance of $81.1 million as of December 31, 2018. The valuation allowance increased by $46.5 million and decreased by $14.5 million during the years ended December 31, 2018 and 2017, respectively.

Internal Revenue Code Section 382 and similar state provisions limit the use of net operating losses and tax credit carryforwards in certain situations where changes occur in the stock ownership of a company. In the event the Company has a change of ownership, utilization of net operating losses and tax credit carryforwards may be limited. Certain acquired net operating losses and tax credits are subject to limitations. Net operating losses and tax credits have been reduced to reflect the amounts that can be utilized to reduce taxes payable in the future.

On December 22, 2017, the Tax Cuts and Jobs Act of 2017 (the “Tax Act”) was signed into law making significant changes to the U.S. Internal Revenue Code. Changes include, but are not limited to, a federal corporate tax rate decrease from 35% to 21%, effective for tax years beginning after December 31, 2017, the transition of U.S. international taxation from a worldwide tax system to a territorial system, and the creation of a Global Intangible Low-taxed Income inclusion (“GILTI”).

ASC 740, Income Taxes, requires companies to recognize the effect of the tax law changes in the period of enactment. However, the SEC staff issued Staff Accounting Bulletin No. 118 (“SAB118”) which allowed companies to record provisional amounts during a measurement period not extending beyond one year from the Tax Act enactment date. The final amount related to the one-time transition tax on the mandatory deemed repatriation of foreign earnings was $0.4 million, which was fully offset with available net operating loss carryforwards. There were no changes to the amount recorded for the remeasurement of certain deferred tax assets and liabilities based on tax rates at which they are expected to reverse in the future and no changes to the amount of benefit recorded related to a valuation allowance release due to tax reform changes in the treatment of indefinite-lived attributes. As of December 31, 2018, the Company completed the accounting for all the impacts of the Tax Act.

The Tax Act subjects a US shareholder to tax on GILTI earned by certain foreign subsidiaries. The FASB Staff Q&A, Topic 740, No. 5, Accounting for Global Intangible Low-Taxed Income ("GILTI"), states that an entity can make an accounting policy election to either recognize deferred taxes for temporary basis differences expected to reverse as GILTI in future years or provide for the tax expense related to GILTI in the year the tax is incurred as a period expense. The results of the Company’s foreign operations did not give rise to a GILTI inclusion in the year ended December 31, 2018.

No additional income taxes have been provided for any remaining undistributed foreign earnings not subject to the one-time, mandatory transition tax, or additional outside basis difference of $4.8 million, as these amounts continue to be indefinitely reinvested in foreign operations.

The Company recorded cumulative unrecognized tax benefits pursuant to ASC 740-10 in the amount of $3.4 million, $1.5 million and $4.3 million during the years ended December 31, 2018, 2017 and 2016, respectively.

The Company’s policy is to recognize interest and penalties related to unrecognized tax benefits within the provision for income taxes. Amounts accrued for interest and penalties were not significant as of December 31, 2018 and 2017, respectively or during years ended December 31, 2018, 2017 and 2016, respectively. During the year ended December 31, 2017, the IRS concluded its audit of the Company’s 2014 tax returns. Upon closing of the 2014 audit, the Company assessed the impact on unrecognized tax positions for all open years and recorded any necessary adjustments. The Company believes that it has provided adequate reserves for its income tax uncertainties in all open tax years. As the outcome of the audits cannot be predicted with certainty, if any issues addressed in the Company's tax audits are resolved in a manner inconsistent with management's expectations, the Company could be required to adjust its provision for income taxes in the period such resolution occurs.

Changes in balances during 2018 and 2017 and ending balances as of December 31, 2018 and 2017 in gross unrecognized tax benefits were as follows:

(in thousands)	December 31, 2018			December 31, 2017
Beginning balances	$	1,486		$	4,273
Increases related to tax positions taken during a prior year		584			2
Increases related to tax positions taken during the current year		1,351			288
Decreases related to tax positions taken during a prior year		(70	)		(2,785	)
Decreases related to tax settlements with taxing authorities		—			(292	)
Ending balances	$	3,351		$	1,486

The Company does not anticipate that the amount of existing unrecognized tax benefits will significantly increase or decrease within the next 12 months.

The Company files income tax returns in the U.S. federal, state, and certain foreign jurisdictions. The Company’s U.S federal income tax return years 2015 through 2018 remain open to examination. The Company’s respective state and foreign income tax return years 2012 to 2018 remain open to examination. There are no income tax audits currently in progress.