Mortgage Servicing Rights ("MSRs") and Related Liabilities - MSR's at Fair Value (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Servicing Asset at Fair Value, Amount [Roll Forward]
Fair value - beginning of period	$ 3,665
Fair value - end of period	3,481
Mortgage servicing rights
Servicing Asset at Fair Value, Amount [Roll Forward]
Fair value - beginning of period	3,665
Servicing retained from mortgage loans sold	66
Purchases of servicing rights	409
Sales of servicing assets	(260)
Changes in valuation inputs or assumptions used in the valuation model	(332)
Other changes in fair value	(67)
Fair value - end of period	$ 3,481
Predecessor \| Mortgage servicing rights
Servicing Asset at Fair Value, Amount [Roll Forward]
Fair value - beginning of period		$ 2,937
Servicing retained from mortgage loans sold		68
Purchases of servicing rights		19
Sales of servicing assets		0
Changes in valuation inputs or assumptions used in the valuation model		239
Other changes in fair value		(69)
Fair value - end of period		$ 3,194

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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