Mortgage Servicing Rights ("MSRs") and Related Liabilities - Servicing Revenue (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Transfers and Servicing [Abstract]
Contractually specified servicing fees	$ 307	$ 245	$ 588	$ 495
Other service-related income	32	28	82	56
Incentive and modification income	10	18	17	33
Late fees	27	22	52	46
Reverse servicing fees	8	14	17	33
Mark-to-market adjustments	(231)	19	(524)	171
Counterparty revenue share	(70)	(50)	(118)	(95)
Amortization, net of accretion	(56)	(48)	(79)	(96)
Total servicing revenue	$ 27	$ 248	$ 35	$ 643

All amounts that, per contract, are due to the servicer in exchange for servicing the financial asset and would no longer be received by a servicer if the beneficial owners of the serviced assets (or their trustees or agents) were to exercise their actual or potential authority under the contract to shift the servicing to another servicer. Depending on the servicing contract, those fees may include some or all of the difference between the interest rate collected on the asset being serviced and the rate to be paid to the beneficial owners of the asset.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 50
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=116651436&loc=d3e122596-111746

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration