Income Taxes (Narrative) (Detail) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Non Variable Interest Entities [Line Items]
NOL carryforward	$ 3,100.0
Alternative minimum tax credit carryforward - Other assets	12.7
Foreign tax credit	61.0
Unrecognized Tax Benefits	0.0
Valuation allowance on net deferred tax asset	$ 923.0	$ 873.0

Non-Variable Interest Entities [Line Items]

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible foreign tax credit carryforwards.

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Amount, before allocation of valuation allowance, of deferred tax asset attributable to deductible tax credit carryforwards, classified as other.

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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 operating loss carryforward, before tax effects, available to reduce future taxable income under enacted tax laws.

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Amount of unrecognized tax benefits.

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