Mortgage Servicing Rights ("MSRs") and Related Liabilities - MSR's at Fair Value (Details) - USD ($) $ in Millions	2 Months Ended	7 Months Ended	9 Months Ended
Sep. 30, 2018	Jul. 31, 2018	Sep. 30, 2017
Servicing Asset at Fair Value, Amount [Roll Forward]
Fair value - end of period	$ 3,485
Mortgage servicing rights
Servicing Asset at Fair Value, Amount [Roll Forward]
Fair value - beginning of period	3,413
Servicing retained from mortgage loans sold	43
Purchases of servicing rights	72
Sales of servicing assets	(63)
Changes in valuation inputs or assumptions used in the valuation model	65
Other changes in fair value	(45)
Fair value - end of period	3,485	$ 3,413
Predecessor
Servicing Asset at Fair Value, Amount [Roll Forward]
Fair value - beginning of period		2,937
Predecessor \| Mortgage servicing rights
Servicing Asset at Fair Value, Amount [Roll Forward]
Fair value - beginning of period	$ 3,413	2,937	$ 3,160
Servicing retained from mortgage loans sold		162	151
Purchases of servicing rights		144	30
Sales of servicing assets		4	(24)
Changes in valuation inputs or assumptions used in the valuation model		330	(113)
Other changes in fair value		(164)	(248)
Fair value - end of period		$ 3,413	$ 2,956

Servicing Asset at Fair Value, Additions, Servicing Retained From Mortgage Loans Sold

No definition available.

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- Definition

The value of new servicing assets, subsequently measured at fair value, acquired or created during the current period through purchases or from transfers of financial assets.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 50
-Section 50
-Paragraph 3
-Subparagraph (a)(2)
-URI http://asc.fasb.org/extlink&oid=68078379&loc=d3e122625-111746

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- Definition

Fair value of an asset representing net future revenue from contractually specified servicing fees, late charges, and other ancillary revenues, in excess of future costs related to servicing arrangements.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 50
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6469459&loc=d3e122501-111745

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 50
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=68078379&loc=d3e122625-111746

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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

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- Definition

Amount of increase (decrease) in fair value from changes in the inputs, assumptions, or model used to calculate the fair value of the contract to service financial assets under which the benefits of servicing are expected to more than adequately compensate the servicer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 50
-Section 50
-Paragraph 3
-Subparagraph (a)(4)(i)
-URI http://asc.fasb.org/extlink&oid=68078379&loc=d3e122625-111746

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- Definition

Decrease in servicing assets subsequently measured at fair value resulting from conveyance of servicing rights to unrelated parties.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 50
-Section 50
-Paragraph 3
-Subparagraph (a)(3)
-URI http://asc.fasb.org/extlink&oid=68078379&loc=d3e122625-111746

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- Definition

Amount of increase (decrease) from changes in fair value classified as other for a contract to service financial assets under which the benefits of servicing are expected to more than adequately compensate the servicer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 50
-Section 50
-Paragraph 3
-Subparagraph (a)(4)(ii)
-URI http://asc.fasb.org/extlink&oid=68078379&loc=d3e122625-111746

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