Income Taxes (Tables)

12 Months Ended

Dec. 31, 2018

Income Tax Disclosure [Abstract]

Components of pre-tax book income (loss)

The components of pre-tax book income (loss) consist of the following:
	Year Ended December 31,
	2018			2017		2016
U.S.	$	(39.7	)	$	26.8	$	(86.6	)
Foreign	(30.9		)	28.6		(164.3		)
Total	$	(70.6	)	$	55.4	$	(250.9	)

Significant components of the income before income tax expense

Significant components of income tax expense consist of the following:
	Year Ended December 31,
	2018			2017			2016
Current:
U.S. federal current expense (benefit)	$	0.0		$	(0.1	)	$	(0.2	)
State current expense (benefit)	(1.1		)	1.2			(0.1		)
Foreign current expense	0.8			12.3			5.7
Total current expense (benefit)	(0.3		)	13.4			5.4
Deferred:
U.S. federal deferred benefit	(1.6		)	(2.5		)	(1.6		)
State deferred benefit	—			(0.0		)	—
Foreign deferred tax expense (benefit)	1.7			(3.3		)	(1.0		)
Total deferred expense (benefit)	0.1			(5.8		)	(2.6		)
Total income tax expense (benefit)	$	(0.2	)	$	7.6		$	2.8

Reconciliation of the statutory U.S. Federal income tax rate to the effective income tax rate on income (loss)

A reconciliation of the statutory U.S. Federal income tax rate to the effective income tax rate on income (loss) is as follows:
	2018		2017		2016
Federal Statutory Rate	21.0	%	35.0	%	35.0	%
Permanent differences	(25.7	)	57.5		7.7
State taxes, net of Federal benefit	3.5		(6.6	)	6.1
Rate change	(0.6	)	370.5		(4.2	)
Foreign earnings taxed at different rates than U.S.	11.8		(40.5	)	(13.5	)
Valuation allowance	81.2		(401.4	)	(27.5	)
Transition tax	(13.8	)	—		—
Net operating loss expiration and remeasurement	(75.8	)	—		—
Changes in uncertain tax reserves	(1.4	)	3.8		(1.0	)
Other	0.1		(4.6	)	(3.7	)
Effective tax rate	0.3	%	13.7	%	(1.1	)%

Significant components of deferred tax assets and liabilities

The significant components of our deferred tax assets and liabilities as of December 31 are as follows:  

	2018			2017
Deferred tax assets:
Accrued postretirement benefit cost	$	40.3		$	39.4
Accrued liabilities	10.9			3.1
Share-based compensation	2.1			1.3
Goodwill	0.4			2.0
Net operating losses and tax credits	482.8			551.1
Foreign basis differences	13.5			13.9
Ravenswood retiree legal settlement	2.4			3.1
Other	1.9			3.1
Total deferred tax assets	554.3			617.0
Valuation allowance	(552.5		)	(607.8		)
Net deferred tax assets	$	1.8		$	9.2
Deferred tax liabilities:
Tax over financial statement depreciation	$	(103.9	)	$	(109.7	)
Total deferred tax liabilities	(103.9		)	(109.7		)
Net deferred tax liability	$	(102.1	)	$	(100.5	)

Changes in valuation allowance

The changes in the valuation allowance are as follows:

	2018			2017			2016
Beginning balance, valuation allowance	$	607.8		$	839.1		$	768.8
Remeasurement of deferred tax assets	(32.1		)	(205.2		)	—
Release of valuation allowance	—			—			(6.0		)
Expiration of net operating losses	(12.3		)	—			—
Other change in valuation allowance	(11.0		)	(26.1		)	76.3
Ending balance, valuation allowance	$	552.5		$	607.8		$	839.1

Significant components of Net Operating Loss Carryforwards

The significant components of our net operating loss carryforwards ("NOLs") are as follows:

	2018		2017
Federal (1)	$	1,470.4	$	1,514.2
State (2)	2,205.0		2,480.5
Foreign (3)	398.2		532.6

⁽¹⁾  The federal NOL begins to expire in 2028.

⁽²⁾  The state NOLs begin to expire in 2027.

⁽³⁾  The Icelandic NOL begins to expire in 2019; the Netherlands NOL begins to expire in 2022.

Reconciliation of beginning and ending amounts of gross unrecognized tax benefits

A reconciliation of the beginning and ending amounts of gross unrecognized tax positions (excluding interest) is as follows:

	2018			2017			2016
Balance as of January 1,	$	8.4		$	6.4		$	3.8
Additions based on tax positions related to the current year	2.0			2.1			2.7
Decreases due to lapse of applicable statute of limitations	(0.9		)	(0.1		)	(0.1		)
Settlements	—			—			—
Balance as of December 31,	$	9.5		$	8.4		$	6.4

Significant components of unrecognized tax positions

The components of our unrecognized tax positions are as follows:

	2018		2017		2016
Highly certain tax positions	$	7.9	$	8.3	$	6.3
Other unrecognized tax benefits	1.6		0.1		0.1
Gross unrecognized tax benefits	$	9.5	$	8.4	$	6.4
Accrued interest and penalties related to unrecognized tax positions	$	0.1	$	0.0	$	—