Income Taxes - Schedule of Effective Tax Rates (Detail) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Federal provision	35.00%	35.00%	35.00%
State provision	0.50%	2.30%	0.20%
Foreign rate differential	(20.00%)	(3.60%)	(7.80%)
Transaction costs	5.00%	0.00%	0.00%
Tax reserves	0.00%	(3.20%)	(2.00%)
Permanent items	10.20%	14.70%	6.00%
Change in valuation allowance(4)	8.20%	20.70%	(5.60%)
Other(5)	0.80%	0.70%	1.90%
Effective rate	39.70%	66.60%	27.70%
Consent Order, Consumer Finance Protection Bureau
Loss Contingencies [Line Items]
Litigation settlement penalty		$ 10.0

Effective Income Tax Rate Reconciliation, Nondeductible Expense, Transaction Costs, Percent

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Effective Income Tax Rate Reconciliation Tax Reserves

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Penalty awarded to (against) the company

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Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to changes in the valuation allowance for deferred tax assets.

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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations applicable to statutory income tax expense (benefit) outside of the country of domicile.

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Percentage of the difference, between reported income tax expense (benefit) and the expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations, that is attributable to tax exempt income, equity in earnings (loss) of an unconsolidated subsidiary, minority interest income (expense), tax holiday, disposition of a business, disposition of an asset, repatriation of foreign earnings, repatriation of foreign earnings jobs creation act of 2004, change in enacted tax rate, prior year income taxes, change in deferred tax asset valuation allowance, and other adjustments.

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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations applicable to state and local income tax expense (benefit), net of federal tax expense (benefit).

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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