
Significant components of income tax expense consist of the following:
	Year Ended December 31,
	2020		2019		2018
Current:
U.S. federal current expense (benefit)	$	—	$	—	$	0.0
State current expense (benefit)	—		(0.1)		(1.1)
Foreign current expense	4.0		0.1		0.8
Total current expense (benefit)	4.0		(0.0)		(0.3)
Deferred:
U.S. federal deferred benefit	(1.2)		(2.2)		(1.6)
State deferred benefit	—		(0.2)		—
Foreign deferred tax expense (benefit)	(5.9)		(6.0)		1.7
Total deferred expense (benefit)	(7.1)		(8.4)		0.1
Total income tax expense (benefit)	$	(3.1)	$	(8.4)	$	(0.2)


A reconciliation of the statutory U.S. Federal income tax rate to the effective income tax rate on income (loss) is as follows:
	2020		2019		2018
Federal Statutory Rate	21.0	%	21.0	%	21.0	%
Permanent differences	(1.2)		(13.1)		(25.7)
State taxes, net of Federal benefit	—		(0.1)		3.5
Rate change	(0.2)		(3.5)		(0.6)
Foreign earnings taxed at different rates than U.S.	(0.3)		(3.3)		11.8
Valuation allowance	(4.3)		72.8		81.2
Transition tax	—		—		(13.8)
Foreign restructuring	(2.3)		—		—
Foreign dividends	(1.5)		—		—
Net operating loss expiration and remeasurement	(10.8)		(66.2)		(75.8)
Changes in uncertain tax reserves	1.4		1.2		(1.4)
Other	0.6		1.0		0.1
Effective tax rate	2.4	%	9.8	%	0.3	%

On January 1, 2019, the Company adopted ASU 2018-02, "Income Statement-Reporting Comprehensive Income (Topic 220), Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income," which provides for the reclassification from accumulated other comprehensive income to retained earnings of stranded tax effects resulting from the Tax Cuts and Jobs Act ("the Act"). In accordance with the provisions of the ASU, $1.3 million of stranded tax effects related to the Act were reclassified from accumulated other comprehensive loss to retained earnings in the first quarter of 2019. This reclassification includes the impact of the change in the federal corporate income tax rate and the related federal benefit of state taxes.

The Company’s accounting policy with respect to releasing income tax effects from accumulated other comprehensive income is to apply a security by security approach whereby the tax effects are measured based on the change in the unrealized gains or losses reflected in other comprehensive loss.

On March 27, 2020, the Coronavirus Aid, Relief and Economic Security Act (the "CARES Act") was enacted in response to the coronavirus ("COVID-19") pandemic. The CARES Act is aimed at providing assistance and health care for individuals, families, and businesses affected by COVID-19 and generally supporting the U.S. economy. The CARES Act, among other things, includes provisions related to refundable payroll tax credits, deferment of the employer portion of social security payments, net operating loss carryback periods, modifications to the net interest deduction limitations, and technical corrections to tax depreciation methods for qualified improvement property. The CARES Act did not have a material impact on the Company’s consolidated financial condition or results of operations for the year ended December 31, 2020. On December 27, 2020, the Consolidated Appropriations Act (“CAA”) was enacted in further response to the COVID-19 pandemic, in combination with omnibus spending for the 2021 federal fiscal year. The CAA extended many of the provisions enacted by the CARES Act, the extension of which likewise did not have a material impact on the Company’s consolidated financial statements for the year ended December 31, 2020.


	2020		2019
Deferred tax assets:
Accrued postretirement benefit cost	$	38.9	$	39.3
Accrued liabilities	7.2		10.8
Share-based compensation	0.7		0.9




Net operating losses and tax credits	430.3		432.8
Foreign basis differences	16.2		15.0
Ravenswood retiree legal settlement	1.7		1.9
Other	10.1		2.8
Total deferred tax assets	505.1		503.5
Valuation allowance	(499.4)		(492.4)
Net deferred tax assets	$	5.7	$	11.1
Deferred tax liabilities:
Derivatives	$	—	$	(3.5)
Tax over financial statement depreciation	(95.0)		(102.4)



Total deferred tax liabilities	(95.0)		(105.9)
Net deferred tax liability	$	(89.3)	$	(94.8)

We regularly assess the likelihood that deferred tax assets will be recovered from future taxable income. To the extent we believe that it is more likely than not that a deferred tax asset will not be realized, a valuation allowance is established. When a valuation allowance is established or increased, an income tax charge is included in the consolidated statement of operations and net deferred tax assets are adjusted accordingly. Future changes in tax laws, statutory tax rates and taxable income levels could result in actual realization of the deferred tax assets being materially different from the amounts provided for in the consolidated financial statements. If the actual recovery amount of the deferred tax asset is less than anticipated, we would be required to write-off the remaining deferred tax asset and increase the tax provision.

We have a valuation allowance of $499.4 million recorded for all of our U.S. deferred tax assets, and a portion of our Icelandic deferred tax assets as of December 31, 2020. The Company is subject to the provisions of ASC 740-10, Income Taxes, which requires that the effect on deferred tax assets and liabilities of a change in tax rates be recognized in the period the tax rate change was enacted. The overall increase in deferred tax assets, and the related valuation allowances, are primarily a result of the generation of Federal net operating loss carryforwards ("NOLs") and U.S. interest expense limitation carryforward, offset by the expiration of certain foreign NOLs.


	2020		2019		2018
Beginning balance, valuation allowance	$	492.4	$	552.5	$	607.8
Remeasurement of deferred tax assets	—		(41.6)		(32.1)
Release of valuation allowance	—		—		—
Expiration of net operating losses	(11.7)		(10.8)		(12.3)
Other change in valuation allowance	18.7		(7.7)		(11.0)
Ending balance, valuation allowance	$	499.4	$	492.4	$	552.5

Our ability to utilize our deferred tax assets to offset future federal taxable income may be significantly limited if we experience an "ownership change" as defined in the Code. In general, an ownership change would occur if our "five-percent shareholders," as defined under the Code, collectively increase their ownership in us by more than 50 percentage points over a rolling three-year period. Future transactions in our stock that may not be in our control may cause us to experience such an ownership change and thus limit our ability to utilize net operating losses, tax credits and other tax assets to offset future taxable income.


	2020		2019		2018
Balance as of January 1,	$	8.2	$	9.5	$	8.4
Additions based on tax positions related to the current year	—		—		2.0



Decreases due to lapse of applicable statute of limitations	(1.7)		(1.3)		(0.9)
Settlements	—		—		—
Balance as of December 31,	$	6.5	$	8.2	$	9.5

Included in the above balances are tax positions relating to temporary differences where there is uncertainty about the timing of tax return inclusion, but not that the amounts will ultimately be tax deductible. Because of the impact of deferred tax accounting, other than interest and penalties, the timing would not impact the annual effective tax rate. The remaining amounts of unrecognized tax benefits would affect our effective tax rate if recognized. It is our policy to recognize potential accrued interest and penalties related to unrecognized tax benefits in income tax expense.


	2020		2019		2018
Unrecognized tax benefits - Temporary Differences	$	5.1	$	6.8	$	7.9
Other unrecognized tax benefits	1.4		1.4		1.6
Gross unrecognized tax benefits	$	6.5	$	8.2	$	9.5
Accrued interest and penalties related to unrecognized tax benefits	$	—	$	—	$	0.1

Our federal income tax returns have been reviewed by the IRS through 2010. However, we have NOLs beginning in 2008 that are available for carryforward to future years. Under U.S. tax law, NOLs may be adjusted by the IRS until the statute of limitations expires for the year in which the NOL is used. Accordingly, our 2008 and later NOLs may be reviewed until they are used or expire. Material state and local income tax matters have been concluded for years through 2016.