Commitments and Contingencies - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019
Litigation and Regulatory Matters
Mortgage Servicing Rights [Line Items]
Legal fees	$ 51	$ 64
Reverse Mortgage Servicing Rights, Excluding Subservicing
Mortgage Servicing Rights [Line Items]
Principal amount outstanding on mortgage servicing rights	18,091	22,725
Reverse mortgage interests, net
Mortgage Servicing Rights [Line Items]
Principal amount outstanding on mortgage servicing rights	18,091	22,725
Maximum unfunded advance obligation	2,202	$ 2,617
Minimum \| Litigation and Regulatory Matters
Mortgage Servicing Rights [Line Items]
Reasonably possible loss	3
Maximum \| Litigation and Regulatory Matters
Mortgage Servicing Rights [Line Items]
Reasonably possible loss	$ 16

Mortgage Servicing Rights [Line Items]

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- Definition

Off-balance Sheet, Maximum Advance Obligation of Reverse Mortgages Serviced

+ References

No definition available.

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- Definition

The amount of expense provided in the period for legal costs incurred on or before the balance sheet date pertaining to resolved, pending or threatened litigation, including arbitration and mediation proceedings.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.3)
-URI http://asc.fasb.org/extlink&oid=120395209&loc=SL114868664-224227

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- Definition

Reflects the estimated amount of loss from the specified contingency as of the balance sheet date.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121557415&loc=d3e14435-108349

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-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 9
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-URI http://asc.fasb.org/extlink&oid=121557415&loc=d3e14557-108349

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 460
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=121555522&loc=d3e12021-110248

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- Definition

This is the sum of principal amount outstanding for both securitized and unsecuritized loans of all types.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121570589&loc=d3e107314-111719

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