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Income Taxes - Additional Information (Details) - USD ($) $ in Millions | 12 Months Ended |  |
--- | --- | --- | ---
Dec. 31, 2018 | Dec. 31, 2017 | Jul. 31, 2018 | Mar. 31, 2018
Tax Credit Carryforward [Line Items] |  |  |  |
Valuation allowance | $ 295 |  |  |
Tax benefit remeasurement of deferred tax assets and liabilities | 3 |  |  |
Unrecognized tax benefits, uncertain tax positions |  | $ 19 |  |
Interest and penalties expense |  | $ 2 |  |
Unrecognized tax benefits, net effect |  |  |  | $ 6
WMIH Corp |  |  |  |
Tax Credit Carryforward [Line Items] |  |  |  |
Valuation allowance |  |  | $ 1,300 |
Federal Net Operating Loss Carryforwards And Other Deferred Tax Assets |  |  |  |
Tax Credit Carryforward [Line Items] |  |  |  |
Release of valuation allowance | $ 990 |  |  |

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- Definition Amount of deferred tax assets for which it is more likely than not that a tax benefit will not be realized. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32537-109319 + Details
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- Definition Amount of expense for interest on an underpayment of income taxes and penalties related to a tax position claimed or expected to be claimed in the tax return. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 15 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32718-109319 + Details
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