Income Taxes - Summary of Components of Net Deferred Income Tax Asset (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Deferred income tax assets (liabilities):
Tax loss carryforwards	$ 423.9	$ 419.7
Tax credit carryforwards	280.6	294.0
Retirement benefit plans	82.9	59.1
Accrued liabilities	177.9	136.1
Self-insurance reserves	7.1	5.8
Current asset basis differences	43.3	43.7
Long-term asset basis differences	(36.5)	(65.4)
Deferred compensation	22.6	27.2
Recoverable customer engineering, development and tooling	67.1	(10.5)
Undistributed earnings of foreign subsidiaries	(71.7)	(76.7)
Derivative instruments and hedging activities	(5.2)	(5.2)
Other	(8.9)	(5.8)
Deferred tax assets, gross, total	983.1	822.0
Valuation allowance	(397.7)	(344.8)
Net deferred income tax asset	$ 585.4	$ 477.2

Deferred Tax Assets, Current Asset Basis Difference

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Deferred Tax Assets, Tax Credit Carryforwards, Net of Stock-Based Compensation Adjustment

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Deferred Tax Liabilities, Long-Term Asset Basis Difference

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences and carryforwards.

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Amount, after allocation of valuation allowances and deferred tax liability, of deferred tax asset attributable to deductible differences and carryforwards, without jurisdictional netting.

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Amount, before allocation of valuation allowance, of deferred tax asset attributable to deductible temporary differences from compensation and benefits, classified as other.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from postretirement benefits.

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Amount of deferred tax assets for which it is more likely than not that a tax benefit will not be realized.

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Amount of deferred tax liability attributable to taxable temporary differences from derivatives.

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Amount of deferred tax liability attributable to taxable temporary differences from undistributed earnings of subsidiary and other recognized entity not within country of domicile. Includes, but is not limited to, other basis differences.

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