Mortgage Servicing Rights ("MSRs") and Related Liabilities - UPB related to owned MSRs (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Owned Service Loans [Line Items]
Fair Value	$ 3,481	$ 3,665
Mortgage servicing rights
Owned Service Loans [Line Items]
UPB	303,692	295,481
Fair Value	3,481	3,665
Credit sensitive \| Mortgage servicing rights
Owned Service Loans [Line Items]
UPB	153,565	135,752
Fair Value	1,626	1,495
Interest sensitive \| Mortgage servicing rights
Owned Service Loans [Line Items]
UPB	150,127	159,729
Fair Value	$ 1,855	$ 2,170

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.

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

Name:	us-gaap_ServicingAssetAtFairValueAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant